WO2001059961A1

WO2001059961A1 - High altitude optical telecommunications system and method

Info

Publication number: WO2001059961A1
Application number: PCT/US2001/003959
Authority: WO
Inventors: Yee Chun Lee; Alexander P. Haig; Elena A. Novakovskaia; Robert W. Phillips, Jr.
Original assignee: Sky Station International, Inc.
Priority date: 2000-02-08
Filing date: 2001-02-08
Publication date: 2001-08-16
Also published as: AU2001234904A1; WO2001059961A9

Abstract

A high altitude laser telecommunications system and method is provided having a novel high altitude platform with an optically clear housing for housing a laser controlled by a fast steering mirror for optically linking high altitude gateway and relay platforms in a chain where each optically linked high altitude gateway and relay platform moves in an independent relationship to each other and the optical links to the chain are maintained by the fast steering mirrors. The novel system and method includes one or more high altitude gateways at each end of the chain with ground-based gateways communicating with the high altitude gateways to allow high data rate communications in the 1 Gigabit per second to 1,000 Terabits per second range through the optically linked chain. Ground-based gateways communicate with the high altitude gateways at extremely high frequency range of from about 100 GHz to 500 GHz and include ground antennae disposed in a manner to accommodate local climatic conditions while maintaining the high data rate communications. The novel system and method of the invention provide a ground to ground telecommunications system of optically linked high altitude chains with systems for bridging the optically linked telecommunications chains that provide an alternative to hardwired coaxial cable and fiberoptic transoceanic and transcontinental cable links.

Description

HIGH ALTITUDE OPTICAL TELECOMMOTTCOVTIONS \ SYSTEM

AND METHOD

BACKGROUND OF THE INVENTION

1. Field Of The invention The invention pertains to a high altitude optical telecommunications system and method having RF . telecommunications links to the ground to provide a ground to ground telecommunications system as an alternative to transoceanic and transcontinental cable links. More particularly, the invention pertains to a high speed and data rate communications system in which RF telecommunications gateways disposed on the ground communicate with high altitude platforms or gateways to provide high speed transmission of data. The ground-based gateways communicate with high altitude gateways in frequencies of 100 giga-Hertz or greater which high speed RF bidirectional communications signals are converted into high speed optical signals to provide a transmission of data in the range of about 1 Terabits per second or greater. The advantages of. the invention are provided in the transmission of data in the range of about one Gigabit per second to 1,000 Terabits per secotid.

The high speed and high volume of optical data signals are transmitted from the high altitude gateway to ^' one or more high altitude relays or to a second high altitude gateway or platform disposed 500 to about 700 kilo eters from the first high altitude relay or gateway. The optical data signals are reconverted at the second high altitude gateway into high speed radio frequency signals for transmission back to the second ground-based gateway in the 100 giga-Hertz (GHz) or greater transmission frequency to provide for the hig speed and high volume transmission of data from a ground to ground telecommunications system. The high altitude gateways and relays are optically linked in a straight line of sight chain which may branch at either end to link with one or mor£ ground-based gateways that interface with local telephone, Internet and telecommunications net o ks.

The systerit and method of the invention also includes the utilization of high altitude relay platforms disposed between the first high altitude gateway and the second high altitude gateway which operate as relay stations to receive and retransmit optical laser signals in the one Terabits per second rate of data. Some of the high altitude relay platforms are designed to receive, split ahd retransmit optical signals in two separate line of sight telecommunications chains, other high altitude relay platforms are designed to receive, split and reconvert a portion of the optical signals into RF signals and transmit one portion of the signals to a satellite or the ground while relaying one or more other portions of the optical signals to other chains that terminate in a combination of a high altitude gateway: nd ground-based gateway combination to provide a high speed high data communications system bridging remote locations. The high altitude relay platforms as well as the first and second high altitude gateways may also include ADD-DROP multiplexers for purposes of dividing laser signals and relaying a portion of the laser signals to a third location or to a satellite when laser communications satellites become available. The high altitude relay stations may also Convert a portion of the optical signals into RF signals and this portion of the signals may be transmitted to either a satellite, third ground-based gateway or a third high altitude gateway to provide an alternative line of communications links to pr vide a high speed high data end to ttiulti-end communications system.

The system and method of the invention in providing an alternative optical data link or RF frequency link to a satellite allows non-instantaneous and low data rate telecommunications to be separated from real time high data rate bidirectional telecommunications so that low data rate telecommunications can be shunted to satellites. The RF frequency link or optical communications link can also be utilized to provide an alternative telecommunications link for purposes of redundancy or specialized communications links for chain bridging capabilities for E-mail or other low data rate types of telecommunications service that tolerate large latencies. i The novel high altitude telecommunications system and method provide for one or more straight chains having line of sight high altitude optical telecommunications capabilities for the high speed transmission o large volumes of data signals. ADD-DROP multiplexers ' in relay high altitude platforms and high altitude gateway platforms allow the splitting and insertion of trunk traffic at those locations in order to provision the trunk traffic from a single origination point to a plurality of destinations_* The novel high altitude optical telecommunications system and method employs ground-based gateways that interface with existing telecommunications infrastructure to provide a high altitude optically linked communications system alternative to the prior art transoceanic and transcontinental linking by coaxial cable or fiberoptic cable telecommunications systems that are currently the state of the art for transoceanic, transatlantic and transcontinental telecommunications requiring the bidirectional real time transmission of high volumes of data.

The novel high altitude optical telecmmunications system and method further contemplates the use f novel features including RF telecommunications between ground- based gateways and high altitude gateways in frequency ranges of above 100 GHz' and preferably in the range of about 150 to 550 GH2 to reduce the si2e of ground antennae as well as the corresponding size of antennae on the high altitude platforms. The novel system and method of the invention further employs high altitude telecommunications platforms having gimbaled lasers which utilize slow steering and fast steering mechanisms for positioning the lasers and interconnecting laser communications with other high altitude optically linked relay and gateway platforms.

The novel high altitude platforms may also utilize optically clear components such as nose covering in combination with diametrically opposed pairs of optically clear communications θds on the nose and tail of the high altitude platform or employ optically clear communications pods on sides of the high altitude platform as well as optic fiber links in the high altitude platform to provide passive- amplification of the optical signals in the high altitude platform. The novel high altitude platforms may also include optical regenerators for amplifying the signals between lasers disposed diametrically opposed to each other on the high altitude relay or high altitude gateway to provide high speed high data telecommunications links in a ground to ground telecommunications system. The novel ground to ground communications system of the invention disposes the components in the upper tropopause_; or in the stratosphere to use the upper tropopause and stratosphere as the transmission medium in a free space optical communications systeft instead of under the ground or under the ocean coaxial cable or optical fiber cables as has heretofore been utilised with transcontinental br transoceanic communications systems.

2. D&aetiήtion Of The Prior Art

A free space optical communication system is basically composed of three parts. First a light source, second a transmission medium and third a detector. The earliest light source, Was the sun which was utilized in a photophone patented in^' 1880 by Alexander Graham ^'Bell. The trans ission medium in that case was the atmosphere. Then, as now, losses encountered in the atmospheric transmission path together with the brightness of the light source, amplification and sensitivity of the detector have imposed limitations on the transmission distance limit of the system. In the case of the photophone, as today with ground-based laser systems, disruptions due to fog, rain and snow and other forms of atmospheric moisture or particles impose severe limitations upon a free space optical communications sys'teitt in the troposphere.

The problems of moisture, particulate matter and atmospheric conditions of the atmosphere as a transmission medium have resulted in first the use of coaxial cables and later the use of fiberoptic cables to link long distances together such as with the transatlantic cable. These transoceanic and transcontinental coaxial communication cable systems have led way to laser communications systems that are now linked by transoceanic and transcontinental fiberoptic cable systems due to the ability of lasers to communicate high volumes of data at high speed.

The fiberoptic cable systems, while providing for the bidirectional transmission of high volumes Of data between and across 'continents, are limited by the fiberoptic systems connecting the lasers and the requirement for such cable to be buried in the ground or follow the deep ocean floor from continent to continent which is a distance equal to or longer than the free space optical communications distance of the invention. Further the prior art fiberoptic systems have required the use of amplifiers and optical signal regenerators due to losses inherent in fiberoptic cables. The fiberoptic cables, amplifiers and regenerators on the ocean floor are also inaccessible and expensive to fix and upgrade, uh ik'e the combination of ground-based gateways, high altitude gateways and relays of the invention.

As a result of the expense and limitations of fiberoptic lines for transmitting large volumes of data at high data rates a number of prior art patents and publications have suggested the utilization of high altitude platforms as a telecommunications station for receiving and transmitting optical signals. The most pertinent of this prior art appears to be the Bozzay, et al_* Publication Nos. O98/35506 and W099/33279 which pertain to the laser communication system between the earth and a satellite or between a high altitude platform and a satellite. Of the two publications W098/35506 appears to be the most relevant in providing for an RF communication link below 50 GHz between the earth and one or more relay systems. The relay high altitude systenti converts the RF signals to Optical signals which are sent to satellites that are optically linked together. The optically linked satellites send the optical signals back to another high altitude relay platform for reconversion of the optical signals back to RF signals that are then transmitted back to earth. The high altitude relay platforms are maintained at a substantially' stationary position at from about 9 (15 km) to 26 (41 km) ttiles above the earth's surface_*

The prior art also recognizes the relationship between RF communications bandwidth, antenna size and power requirements. Bozzay, et al. Publication WO98/35506 (Fig. 1C) recognizes that large antennae are required to transmit narrow beams and that antenna size is a key problem for satellites. Antenna size can be reduced by utilizing higher RF frequencies however the advantages of higher RF frequencies are limited by attenuation problems which result in practical radio frequency communications with satellites below 50 GHz due to 'atmospheric losses. The RF frequency limitations of below 50 GHz are based upon tables and software calculations of the prior art that describes the disadvantages of utilizing frequencies above 50 GHz.

The advantages of the invention are in part due to the findings that the impact specific attenuation due to rain and moisture flattens out at frequencies higher than 70 GHz and the development of a specific equation that provides specific information for the effects of rain attenuation for specific frequency. This discovery in combination with providing multiple ground gateways provides for the communications of broadband high speed and data rate and volume communications With high altitude platforms having smaller antenna arrays consistent with the performance ' capabilities of high altitude platforms. .

Unlike the present invention Publication O98/35506 utilizes RF communications below 50 GHz and utilizes a bandwidth o about 5 GHz due to problems of RF frequency communications below 50 GHz due to atmospheric and technical limitations. Further the high altitude platform and optical link with satellites in accordance with Publication WO98/35506 provides for data rates of 5 Gigabits per second rather than the one Terabits or greater per second as utilized in accordance with the invention. The method and system of the invention is distinct ^rom the inventions in Bo2zay Publication Nos. WO98/35506 and

W099/33279 in providing for a high data rate, high speed telecommunications _; system in which RF frequencies at or above 70 GHz are utilized between the ground gateway and the high altitude gateway to provide for the optical transmission of Terabits per second of data signals from the high altitude gateway to high altitude relays before the optical signals are reconverted by a remote high altitude gateway into RF frequencies at or above 70 GHz that are then communicated back to a remote ground-based gateway. The invention contrasts from the prior art by providing a high volume high data rate RF communications link between the ground-based gateway and the high altitude gateway to enable the optical laser link in the high tropopause or stratosphere to cortifttuhica e at the rate of Terabits per second. All this is accomplished without the problem of latency and power requirements for communicating with satellites. ^:

A number of prior art systems pertain to optical communications systems between satellites with RF communications from ground gateways to satellites. Although all known communications in operation utilize RF communications links,' optical links between various types of satellites, including GEO (geosynchronous earth orbit) and LEO (low earth orbit) satellites are disclosed in Grant, et al. U.S. Patent NoS_* 4,933,928 and 5,119,225. These combined RF communication links to satellites With optical links to GEO and LEO satellites are different from the present invention which provides for not only high speed but also high volume a d data rate transmissions utilizing smaller antennae for a given power and optical system size. In part due to the difference in distance between a ground gateway and a satellite or a ground gateway and a high altitude gateway platform, for a given antenna Size and a given laser size, a high altitude platform provides for higher speed and greater volumes of communications while requiring far less laser and RF power.

Ultrahigh Speed optical data links for interactive video and the Internet require high volume and data rate communications that cannot be provided by satellites but can be provided by hardwired fiberoptic systems and by the high altitude optical telecommunications system and method of the invention. One of the reasons is that geostationary satellites are typically 36,000 kilometers (22^320 mi) above the earth while the high altitude platforms of the invention are typically deployed at an altitude of about 15 km (9 mi) to 41 km (26 mi) above the surface of the earth resulting in less time delays for RF communications to go to and from the high altitude platform as opposed to going to and from a geostationary satellite, in addition due to antenna size limitations for satellites, bit rate for high speed communications with geostationary satellites is limited.

In contrast to the satellite prior art the distance between the RF ground gateway and the high altitude gateway and relays to high altitude gateway to ground gateway is actually less than the distance of the transoceanic fiberoptic cable following the contours of the ocean floor. The substantially instantaneous transmission between the high altitude gateway and the relays through optical telecommunications allows the novel system and method of the invention to provide for both high speed and high data rate and volume bidirectional real time telecommunications from ground to ground than can be provided by satellite communications systems. in general a high altitude platform Is disposed between about 15 km (9 mi) and 41 km (26 mi) above the earth's surface in the high tropopause or stratosphere as opposed to a LEO satellite constellation which is disposed at about 1,400 kilometers (868 mi) from the earth's surface and a MEO satellite constellation which is disposed at about 10,100 kilometers (6,200 mi) above the earth's surface, while a GEO satellite is located at about 36,000 kilometers (22,320 mi) above the earth's surface. The losses in communication between a ground gateway and a high altitude gateway platform using for example 300 GHz in accordance with the invention are 168 dB at 20 kilometers above the surface while the losses between a ground gateway and a LEO are about 37 dB highe (205 dB in total) while the losses in communication ro the^! ground gateway to a MEO are about 54 dB higher (222 dB in total) and for a GEO the losses are about 65 dB higher (233 dB in total) . These additional losses result in decreases in bit rate. For example with a LEO the data rate is reduced by a factor of 5 x lO³ while for a MEO the factor is 250 x 10³ while for a GEO the factor is 3 x 10⁶.

A number of prior art patents generally discuss optical communications between high altitude platforms without describing the type of communications link with the ground or any particular frequency as it relates to antenna size on the high altitude platform or on the array on the ground. Included in such prior art is McNultey latent Application GB 2 082 995, Wong U.S. Patent Nos_* 5,678,783 and 5,912,396 as well as Paulson U.S. Patent No_* 6,010,093 and a Japanese Publication entitled Stratospheric! Platform (November, 1999). ^: ϊή έuch prior art the laser communication links between high altitude platforms are arranged to provide a network of geostationary platforms to provide a regional or global telecommunications network.

None of these prior art references alone or in combination discuss an_: optically linked line of sight chain of high altitude platforms to provide transocea ic or transcontinental cd unicatiσns systems for replacing high speed, high data rate transatlantic or transoceanic ground- based cable systems. This high altitude platform art, like the satellite prior art, provides for a global array of high altitude platforms¹ in a geodesic pattern. Wong U.S. Patent No. 5,678,783 (Fig*, 11) which like the geodesic_. rray provided for by satellites in Bloom, et al. U.S. Patent No. 5,710,652 (Fig. 2) provides an integrated communications coverage for the entire earth.

In accordance with the invention it has been found that it is neither necessary nor desirable to provide a fully integrated geodesic pattern of high altitude platforms to cover the entire globe unless the communications system is a cellular communications system. In contrast the invention provide for one or more line of sight chains of high altitude platforms in combination with one or more ground gateways that interface with existing I, telecommunications networks to replace transoceanic cable and transcontinental cable links. Unlike the prior art the present invention pertains to a ground to ground system for replacing transoceanic and transcontinental cable systems with a free space optical communications system that utilizes the high troiόpause and stratospheric atmosphere as the link between lasers that are arranged in substantially straight chains that link continents together Without the necessity of providing for an entire geodesic high altitude platform system.

A complete global geodesic arrangement of high altitude platforms' is' also neither necessary nor desirable to provide a ground to ground and ground to multi-end communication links utilizing the method and system of the invention. It has aϊέό been found that it is neither necessary nor desirable to use a ground gateway to connect a high altitude gateway with optical links to satellite to satellite as is described in the prior art. As a result the invention unlike the prior art utilizes single chains' which provide a practical end to end communications system by employing a ground gateway with a high altitude gateway to connect the substantially straight line of sight chain of high altitude relay platforms to a high altitude gateway platform. The invention also provides for ADD-DROP multiplexers for dividing signals between high altitude platforms. as ell as optical to RF signal converters to provide for the division of communications between high altitude platforms and satellites in alternative chain arrangements. The invention unlike the prior art employs a combination of ADD-DROP multiplexers with optical to RF signal converters to provide an alternative path for telecommunications between the high altitude platform and existing satellites of either LEO, MEO or GEO class to provide redundancy and/or to provide for low volume low data rate forms of communication tolerable to higher latencies such as E-mail. The invention further provides for broadband RF communications between ground gateway and high altitude gateway as well as for the narrow band RF communications between high altitude gateway or relay with existing satellites through existing ^'RF communication links as well as for the provision of optical links with satellites when they become available on telecommunications' satellites.

The communications between ground and satellite in all systems known to be in use utilize RF communications even though a number of patents as heretofore discussed propose optical communications links between a high altitude platform and existing satellite systems. In addition all communications between the satellites as known to be in use are currently RF communications links as opposed to the optical links as described in some of the prior art. Notwithstanding these limitations in actual use it is contemplated that, when such optical links between satellites become commercially available, the invention can be readily changed over to optical communications links with satellites in the satellite system by merely substituting or adding one additional high altitude relay or gateway in the optically linked chain to provide redundancy and alternative pathways for lower bit rate communications . In contrast to hardwired telecommunications cables the present invention is readily adapted for modification or maintenance without removing the cable front the ocean floor or from the ground. Unlike the prior art the system and method of the invention contemplates the use of terrestrial gateways utilizing an extremely high frequency of about 70 GH2 to 550 GHz and preferably about 100 to 300 GHz to Commnicate with a gateway high altitude platform disposed in the high tropopause or stratosphere. Unlike the prior art it has been discovered that attenuation and scattering effects of these higher frequencies at lower altitude are,not as great as contemplated by the prior art. It has been discovered that at higher rain and moisture rates the specific attenuation due to rain flattens out at frequencies above 70 GHz and that a specific formula provides specific attenuation data for a specific frequency.

Therefore unlike the prior art of Bozzay, et al. Publication No. W099V33279 and WO98/35506 the present invention provides an extremely high frequency communications link between the ground-based gateway and the high altitude gateway in accordance with the method and system of the invention. The extremely high-f equency RF communications link of above 70 GHz is needed to provide both high speed and high data rate communications between the ground-based gateway and the high altitude gateway to efficiently take advantage of the high data rates of 1 Terabits per second or greater that can be achieved by optical transmissions between high altitude gateway and high altitude gateway or high altitude gateway and to high altitude relay to high altitude relay to high altitude gateway in the optidaliy linked chain. In U.S. Patent No. 5,949,766 a high altitude gateway platform is provided for cellular and satellite communications that is Similar to that provided for in the high altitude platform system in Bozzay, et al_* W099/33279 and WO98/35506. The high altitude gateway in U»S, Patent No. 5,949,766 for communicating with satellites provides for communication utilizing optical or radio frequency links between the ground and high altitude platform and satellites. U.S. Patent No. 5,949,766 further cites the application of Sky Station International, Inc. before the Federal Communications Commission on March 20, 1996 as prior art which describes RF¹ communications with high altitude platforms and laser communications links between platforms but does not teach or describe a combination of ground gateways with high altitude gateways and relays ' for providing an optically linked chain for replacing cable or fiberoptic cable for transatlantic, transoceanic and transcontinental communications.

The invention provides for line of sight chainlike communication between high altitude platforms employing optical lasers to ptovide the Terabits per second high volume high speed data communication links across the tropopause or stratosphere with high bandwidth frequency communications from* ground gateways to high altitude gateways disposed at either end or one or more multiple gateways at the end of the optically linked chain. In achieving these advantages the invention utilizes many prior art subcomponents such as optical signal transceivers, dense wavelength division multiplexers, fast steering mirrors combined with gimbaled lasers and fast motor drives for providing for fast, έtήgular adjustments of optically linked lasers on moving high altitude platforms. Som of these components are subject to separate patents such as Rice U.S. Patent No. 5,347,387 and Nower, et al. U.S. Patent No. 5,684,578 which are illustrative of the optical laser pointing art.

In addition to the prior art components and assembling the components in a novel arrangement, the invention also utilizes novel components and subcomponents to achieve the advantages of the invention. Novel components utilized to provide additional advantages for the invention include an optically clear nose or area in the nose of a high altitude platform which is utilized as a housing for a novel articulated laser utilizing both a mechanical glmbal and a fast steering mirror to. ove a light beam quickly and point it to a specific direction and stabilize the light beam.

This combination of a mechanically gimbaled laser and a fast steering ^'mirror ensures optical link continuity of transmission and reception between optically linked platforms in the optical chain as individual platforms constantly move in relationship to each other in response to changes in altitude, longitude and latitude as a result of changes in atmospheric conditions and propulsion requirements. The invention also utilizes a high speed motor for moving the laser in combination with mechanical means for allowing the laser to tapidly travel 90° to its horizontal axis in any direction to accommodate the relative positional relationship between high altitude platforms in the upper tropopause¹ and stratosphere as well as to provide telecommunications redundancy by shunting all or a portion of the communication signals to a satellite or to provide for telecommunications chain bridging. The optically clear nose or an area in the nose and the mounting of a laser within the optically clear nose or area of the nose of a high altitude platform has not been uncovered in the prior art. The most relevant patent pertaining to an optically clear airship is Peterson U. S . Patent No. 5,115,997 Which discloses an airship hich is virtually, if not entirely, invisibly transparent. U.S. Patent No. 5,115,9^7 does not disclose an optically clear nose as opposed to other portions of the airship or disclose the application of an optically clear nose as a housing for laser communications.

The prior art has not utilized a high speed high data rate frequency for linking a ground-based gateway with a high altitude gateway for interconnecting a chain of line of sight relay platforms in a ground to ground communication system utilizing at both ends a high altitude gateway for communicating with a ground-based gateway utilizing extremely high RF communication links to provide,a high speed, high data rate communications link to aliow Terabits of information to be' transferred from one ground station to another remote ground gateway station.

The prior art has not provided a system wherein one or more of the high altitude gateway or high altitude relay platforms utilize an ADD-DROP multiplexer for dividing the optically transmitted signal into one or mote branching chains to provide ground to multiple ground point or multiple ground point to multiple ground point, communication systems for replacing transoceanic and transcontinental interlinking communications systems. The prior' art has not provided a system of failsaf or alternative routes rom ground gateways to relay stations to satellites to provide a failsafe communication system or a communication system where low volume or low data rate signals either optical or radio frequency are separated from high, volume high data rate bidirectional real time communication signals. Further the prior art has not provided for a systeM of cable or optical chain bridging utilizing one or more high altitude gateway or relay platforms to provide fo satellite bidirectional communications for chaih bridging communications between optically linked communications chains. The prior art has also not provided an optically linked high altitude system of relays and gateways to replace the transoceanic and transcontinental communications cables of the prior art. SϋMMARY OF THE INVENTION

The invention provides for a high speed, high data rate telecommunications system utilizing a combination of ground-based gateways- and high altitude gateways in combination with an optical telecommunications system for replacing the expensive and inefficient coaxial cable and fiberoptic cable systems of the prior art. The invention utilizes an RF gateway system capable of the bidirectional communication of one Terabits per second or greater by utilizing an extremely high RF frequency link of about 70 GHz band up to about 550 GHz and preferably between 275 - 550 GHz between a ground-based terrestrial gateway and the high altitude platform gateway. Thereafter optical links are utilized in combination with high altitude relay stations and high altitude gateway stations to optically link the high altitude gateways with a ground-based terrestrial gateway, at a distant location.

The advantages of the invention are achieved by utilizing a geostationary high altitude pla forϊft maintained at a geostatic position with respect to the earth's surface in relation to position and altitude. The geostatic position with respect to a point on the earth's surface must be maintained within a cylindrical area having diameter of about 1 km (.62 mi) to 10 km (6.2 mi) and the geostationary position within an altitude of about 1 km (.62 mi) to 3 km (1.9 mi). High altitude platforms that are capable of operating in the upper atmosphere, which, for the purposes of the invention, is an altitude of 15 to 41 kilometers (9 to 26 miles) which is preferably in the high tropopause or stratosphere above the Jetstream and most dense atmosphere. High altitude platforms (gateway or relay) may pitch, roll or yaw up to about 90 degrees to each other and still maintain the optical communications link by Utilizing the gimbaled laser and fast steering mirror combination as will be described hereinafter in greater detail.

High altitude platforms capable of maintaining a geostationary position or geostatic position within these limits are referred to hereinafter as high altitude gateway, high altitude relay or high altitude platforms, Lighter- than-air aircraft generally include a lifting gas, a thermal management system along with propellers or other propulsion means for maintaining the aircraft within the altitude and positional requirements. Aircraft that are not, lighter- than-air require a wing, either stationary o rotary, and propulsion means to fly within the prescribed geostationary or geostatic position_*. Hybrid aircraft utilize both, a lifting gas and a wing, either rotary or fixed, to supplement the lifting gas to hover or fly within the prescribed geostationary or geostatic position. All such aircraft are included In the meaning of high altitude aircraft that constitute a high altitude relay or high altitude gateway in accordance with the invention. The high altitude platform, whether manned or unmanned, must be able to provide an optical link between two gateway high altitude platforms or between a gateway high altitude platform and one or more relay high altitude platforms maintained in a line of sight chain to provide optical links between the platforms.

Since a laser beam does not bend an optical link must be maintained within a line of sight to provide an optical link with a second laser disposed on another high altitude platform_* The high altitude platforπt is maintained at a distance from about 500 to 700 kilometers from each other high altitude platform to prevent impingement of the laser beam on the denser atmosphere at the lower altitudes below the high altitude platform. The optical lihk between high altitude platforms is provided by lasers which are gimbaled to provide a 360 degree articulation around the center axis of the laser and at an angle of about 90 degrees to the center axis of the laser beam. The 360 degree articulation within about a 1 to 3 degree angular travel up, down, right, left and all degrees around a 360 degree angular travel is constantly controlled by a fast steering mirror to provide and maintain an optical link with a similarly disposed laser in a high altitude platform disposed at a distance from about 500 to 700 kilometers. The lasers Utilized are preferably laser transceivers that utilize fast steering mirrors to move the laser beam quickly and point it to a specific direction and then stabilize it in that direction. This is necessary so that a corresponding fast steering mirror associated with the corresponding laser transceiver on the second high altitude platform is capable of intercepting the laser beam from the first high altitude platform to provide an optical link between the two platforms. This optical link allows about 2 degrees of freedom from the central axis of each of the laser transceivers to allow both fast steering mirrors in the lasers to quickly intercept and stabilize the light beams from the optically linked high altitude platforms to provide a communications link. The relay high altitude platform in the best mode includes sets of two separate laser transceivers on each high altitude platform for receiving and transmitting optical signals. Each set of laser transceivers is directed to one particular side of the high altitude platform to provide laser communications to platforms on either side of each high altitude platform. The first laser transceiver with a fast steering mirror connects first high altitude platform to one of the optical transceivers on the second high altitude platform. Within each set the first laser transceiver on the first high altitude platform is optically connected to a second optical transceiver on the first high altitude platform. Preferably the first laser transceiver and the second optical transceiver on each high altitude platform are interconnected by an optical fiber. Preferably the first and second laser transceivers are disposed at diametrically opposed locations on the high altitude platform to receive and transmit the optical signals. Additional sets of laser transceivers may be added for redundancy or provided for future expansion of the optically linked chain.

The optical fiber connecting the first optical transceiver with the second optical transceiver oh the relay high altitude platform or the gateway high altitude platform may also include either or both passive amplification means as well as active amplification means. Preferably the high altitude platform employs passive amplification means for providing amplification of the optical signals.

The relay high altitude platform may also include ADD-DROP multiplexers for dividing received or transmitted optical signals and transmitting the divided optical signals to two different relay or gateway high altitude platforms. The relay high altitude platforms may also include an RF multiplexer for transmission of a portion of the divided optical signals as RF si ials to a ground gateway or to a satellite to provide for redundancy, a shunt for signal requiring lower speed or data rates, such as E-mail, or to provide for chain bridging between two different chains. The high altitude gateway platforms generally include RF communications transceivers and antenna with an RF to optical signal converter. The high altitude gateway platforms also include an optical laser transceiver and may also include an ADD/DROP multiplexer for transmitting optical signals to two different high altitude platforms. The high altitude gateway platforms may also include a second RF transceiver for communicating with a satellite to provide for bridging of chains or for purposes of redundancy.

The high altitude platforms not only include the optical laser transceivers with fast steering mirrors for providing optical communications links between high altitude platforms but also a motor for moving the entire laser 90 degrees to its center axis in any direction, and, if desired, to point the laser toward a satellite to provide redundancy or an alternative optical link for chain bridging. Redundancy is provided for in the event that one of the relay platforms or one of the high altitude gateway platforms are taken out for maintenance or have been incapacitated. Since most of the satellites now available, i.e. LEO (low earth orbit), MEO (middle earth orbit) and GEO (geosynchronous earth orbit) utilize RF signal transmissions the invention contemplates the alternative redundancy link by connecting existing RF satellite communications with either a relay platform or a high altitude gateway platform having a second RF transceiver for providing corresponding radio frequency signals compatible with existing satellites. Satellites can be used in an emergency to transmit the RF signals back to either a high altitude platform gateway or a ground-based gateway to provide redundancy in the system.

The redundancy aspect of the invention can also be utilized for low data rate or with large latency communications where high data rates are not necessary such as in E-mail communications. It is contemplated that in accordance with the invention high altitude platforms can communicate with satellites either through the traditional radio frequency communications or through optical links when such become available in satellites. These lower speed messages can be separated at the high altitude platform with an ADD-DROP multiplexer and communication signals not requiring instantaneous bidirectional communications or interactive video, such as utilized in E-mail, can be separated from high speed transmissions to allow such low data rate communications to be shunted to a satellite, whereas interactive video and high data rate communications are sent through the optically linked high altitude platforms to a high altitude gateway for subsequent retransmission to a ground-based-gateway which is interfaced with existing ground-based telecommunications systems. In addition the high' altitude gateway at the signal destination may also include ADt>-DROP multiplexers for dividing a portion of the signal for retransmission to another chain of high altitude gateways or relays for transmission to different destinations.

The advantages of the invention are achieved utilizing optical transceivers disposed on high altitude platforms to transmit optical signals with a wavelength in the range of 1.3 to 1.5 microns (10"⁶ m) . The radio frequency communication link between the terrestrial gateway and the high altitude gateway is in the extremely high frequency range of 70 GHz up to about 550 GHz and preferably in the range of about 100 to 300 GHz to provide higher antenna gain and reduce the antenna size that must be carried by the upper tropopause or stratospheric high altitude platform*

Communications between a ground-based gateway and high altitude gateway are not affected by tropospheric conditions in hot and humid weather as much as originally believed. In the course of studies leading to the invention a formula was developed which provides specifid information as to specific frequencies for losses due to attenuation for rain. The formula confirms the results of the prior art at the specific parameters studied by the prior art. It demonstrates that losses due to attenuation in even heavy rain at frequencies above 70 GHz flatten out and are only weakly dependent upon rain and moisture in the air. Further, it provides information in specific rain attenuation that interpolates from those studies of the prior art. It was believed, owing to the difficulties in computing rain attenuation losses at frequencies above 70 GHz, that frequencies above the 50 GHz range would be more affected by tain and moisture in the atmosphere than was discovered in calculations conducted in accordance with the invention.

As a result the RF communication link between the ground-based gateway" ahd the high altitude gateway utilize frequencies at or greater than 100 GHz to reduce the size of the antenna disposed on the high altitude platform.

Attenuation losses due to heavy rain are accommodated in accordance with the invention by adequate link margins and providing a plurality of ground gateway stations separated by a distance sufficient to accommodate local Climatic conditions and heavy weather cells. Typically ,the ground gateway stations are separated by about 10 kilometers to provide spatial diversity since in most places this is the largest size of a heavy rain cell or storm that would be sufficient to disrupt RF communications. In some temperate climate zones, where large rain cells may blanket an area of greater than 10 kilometers (6.2 mi) , and in such cases the invention separates the plurality of ground-based antennae for the ground-based gateway with a distance commensurate to accommodate local climatic conditions. As a result the transmission antennae for the ground-based gateway are arranged in accordance with climatic condition and separated by typical rain cell sizes encountered in heavy or severe rain conditions to provide alternative terrestrial antenna sites for communicating with the high altitude gateway. In accordance with the best mode of the invention an antenna such as the coherent dish array is utilized to transmit and receive RF signals on the same frequency between the ground-based gateway and.the high altitude gateway.

Links between the high altitude gateway and the high altitude relay platforms are all optical links to provide high speed high data rate communications using optical laser links between the platforms to provide a bidirectional transmission of data at a rate of 1 Terabits per second or greatet_* The 1 Terabits per second data rate is based upon the utilization of an aperture of the optical system of about 5 to 20 centimeters and utilizing a power of about 1 to 20 Watts. . Obviously, if larger lasers are utilized, or greater power is utilized, or the RF frequencies betwee the ground-based gateway and the high altitude are increased, the volume of data and signals transmitted through the novel system can be similarly increased. The high altitude gateway and relay platforms may include optically clear area in the nose or optically clear nose cones or laser housing pods for housing the' optical laser transceiver fόt receiving and transmitting laser communications. In addition the high altitude platform may include optical fibers internally mounted within the skin of the high altitude platform to connect the laser transceivers on each of the high altitude platforms. Active and passive amplification of the optical signals may also be provided for on the high altitude platform. The novel method and system of the invention also preferably utilizes dense wavelength division multiplexing to provide high speed communication to efficiently and simultaneously transfer multiple wavelengths. The method of the invention provides for the utilization of a chain of optically linked platforms analogous to the coaxial or fiber optic communications cables that have bee laid across the ocean or buried transcontinentally in the ground. The method of the invention provides for optically linked chains that terminate in ends having a high altitude gateway coupled to a terrestrial based gateway. These optically linked chains may have a single ground gateway linked to a single high altitude gateway or ends with multiple high altitude gateways with each high altitude gateway linked by an RF telecommunications iink to a ground-based gateway which interface with an existing telecommunications . infrastructure. In this manner the invention provides an alternative to the telecommunications cables deployed across continents and oceans to provide telecommunications capabilities.

The method of the invention further contemplates the creation of a ground-based gateway and a high altitude gateway suitable for Optically interconnecting with any of the optical chains provided in accordance with the invention. The invention further provides for bridging of optically linked chains while providing high data rate, high speed telecommunications utilizing frequencies at or above 100 GHz to provide the necessary broad bandwidth for communication to allow Terabits of information to be transmitted between high altitude relays and gateways.

BRIEF DESCRIPTION OF THE DRAWING

The objects and advantages of the invention will become more apparent to those skilled in the art from the following Description of the Preferred Embodiment in relation to the accompanying drawings in whichJ

FIG. 1 is a top planar projection of the world illustrating two of the optically linked chains of the novel high altitude optical ' telecommunications system with an optional satellite linkage bridging the optically linked chains;

FIG. 2 is an elevational view comparatively illustrating data losses and time delays in satellite telecommunications uέing for example a frequency of 300 GHz for comparison with the data losses and time delays utilizing the novel high altitude optical telecommunications system of the invention;

FIG. 3 is a prior art ground to ground telecommunications system utilizing high altitude platforms as gateways to satellites telecommunications;

FIG. 4 is an elevational view illustrating an embodiment of the novel high altitude optical telecommunications system of the invention;

FIG. 5 is a graph illustrating a comparison between a LEO, MEO or GEO satellite and a novel high altitude platform with an onboard antenna size of 2.5 meters in relation to transmission frequency and bit rate per link;

FIG. 6 is a graph illustrating a comparison between a LEO, MEO or GEO satellite and a novel high altitude platform with an onboard antenna size of 1 meter in relation to transmission frequency and bit rate per link; FIG. 7 is a graph illustrating a comparison between a LEO, MEO σ GEO satellite and a novel high altitude platform with an onboard antenna size of 0.75 meter in relation to transmission frequency and bit rate per link; FIG. 8 is a prior art graph illustrating specific attenuation due to rain in relation to RF frequency in giga- Hertz;

FIG. 9 is a comparison of specific attenuation due to rain up to the 1,000 GHz limits of the prior art; FIG. 10 is an elevational view illustrating a further embodiment of the novel high altitude optical telecommunications system of the invention;

FIG. 11 is an elevational view illustrating the positional relationships between high altitude gateway platforms and high altitude relay platforms for providing the advantages of the invention;

FIG. 12 is a side elevational view illustrating various types of high altitude aircraft for use as high altitude gateway and relay platforms for achieving the advantages of the novel high altitude optical telecommunication system of the invention;

FIG. 13 is a ide elevational view illustrating optical laser links between high altitude platforms with the angular links withih the control of fast steetiiig mirrors; FIG. 14 is a further embodiment of the invention illustrating additional applications for the novel high altitude optical telecommunications system of the invention; FIG. 15 is a diagrammatic view illusttating the various electronic components that can be utilized in the high altitude gateway and high altitude relay platforms in accordance with the invention;

FIG. 16 is a side view of an embodiment of a high altitude relay platform of the novel high altitude optical telecommunications system of the invention;

FIG. 17 is a further embodiment of the high altitude relay of FIG. 16;

FIG. 18 is a further embodiment of a novel high altitude relay of the novel high altitude optical telecommunications system of the invention;

FIG. 19 is an elevational view of an embodiment of a high altitude gateway platform of the novel high altitude optical telecommunications system of the invention;

FIG. 20 is a side view of a high altitude platfotm having an optically clear portion of the nose and optically clear pods for housing a laser in accordance with the novel high altitude telecommunications system of the invention; FIG. 21 is a schematic view of an optical laser with a 2 degree of freedom gimbal and a fast steering mirror for use in the high ^; altitude telecommunications system of the invention; and

FIG. 22 is a perspective view of the base supporting the laser and a fast steering mirror for use in the novel high altitude optical telecommunications system of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 the invention provides an alternative to ground and transoceanic telecommunications cables from one point 18 such as Washington, D.C. on the earth 20 to another point 22 such as Lisbon, Portugal on the earth 20 utilizing an optically linked chain 24 of high altitude relay platforms 26 having a high altitude gateway platform 28 at the ends of the chain 24. The high altitude gateway platforms ,28 are also optically linked to the high altitude relay platforms 26. The high altitude gateway platforms 28 at eithet end of the optically linked chain 24 are linked via RF Signals to a ground gateway 30 (Fig. 4) at either end of the optically linked chain 24 to provide a high speed data communications system capable of carrying high volume of data signals in not only Gigabits but above and beyond one Terabits (10¹² bits per second) to about 1,000 Terabits per second.of communication signals _*

. Referring o^t to FIG. 1 and 4 the invention provides for transoceanic and transcontinental high speed high data rate communications by utilizing at least one high altitude gateway platform 28 linked by an RF communications link to a ground gateway 30 through at least one ground antenna 32 communicating with a corresponding high altitude antenna 34 disposed oh the high altitude gateway 28. The RF communications link between the ground antenna 32 and high altitude antenna 34 is preferably in the extremely high radio frequency range of about 100 GHz to about 550 GHZ; Preferably the RF link between the high altitude gateway and the ground gateway is in the range of 120 GHz to 300 GHz or greater as higher fadlό frequencies allow reduction in the size of ground antenna 32 and corresponding high altitude antenna 34 as will be described hereinafter in greater detail.

As illustrated in FIGs. 1 and 4 the first high altitude gateway 28 includes an RF to optical converter 36 to convert the radio frequency signal into optical signals which are then transmitted by a first laser 38 to a second laser 40 located on the second high altitude gateway 42 which also includes¹ an RF to optical convertet 36 fot converting the optical signals transmitted through the optical link back into radio frequency signals* The reconverted radio frequency signals are transmitted back across a second RF link preferably also at an extremely high frequency of 100 giga-Hertz band or greater back to a second ground antenna 44 to a second ground gateway 46 disposed at a remote distance of from about 200 to 700 kilometers from the first ground gateway 30. In applications where the distance between the first ground gateway 30 and the second ground gateway 46 is more than 700 kilometers one or more high altitude relays 26 are disposed between the first high altitude gateway 28 and the second high altitude gateway 42 to optically link high altitude gateway 28 with high altitude gateway 42.

One or more of the high altitude relay platforms 26 or high altitude gateway platforms 28 and 42 may include an optical or radio frequency link to a satellite 48 to link optically linked chain 24 to a third high altitude gateway 50 near Cape Town, South Africa, or to a second optically linked chain 52 with a link to a fourth high altitude gateway 54 disposed near Rio de Janeiro, Brazil. The optical or radio frequency link between a high altitude relay 26 or a high altitude gateway 28 in chain 24 with satellite 48 and between satellite 48 and a high altitude relay or high altitude gateway in chain 52 may be utilized to bridge two optically linked chains.

Alternatively satellite 64 is used to link with high altitude relay, high altitude gateway or from satellite 64 to a ground station for purposes of providing communication redundancy_* Satellite 64 can also be utilized for communication setvices which do not require vast amounts of data such as E-mail or between two remote locations. In contrast communication services requiring high data rates such as real time video conferencing and bidirectional video telephone require the bidirectional communication of high volume digital signals through ground-based communications cables or the optically linked chains in accordance with the invention.

Referring now to FIGs. 1, 3 and 4, the distinction between the prior art and present invention are readily apparent. The prior art Fig. 3 employs a ground station 51 for providing an RF communications link with a first stratospheric platform 53 which serves the function of a relay or gateway to a satellite 55. The RF signals may be transmitted to satellite 55 or converted to optical signals which are transmitted to satellite 55 which theh retransmits those signals either in an optical or an RF mode to the second stratospheric platform 57 which signals are (in the case of RF signals) relayed to a second ground station 59 or if the RF signals Were converted by the first stratospheric platform 53 into Optical signals then the second stratospheric platform 57 reconverts those optical signals into RF signals for transmission to the second ground station 59. In the prior art the satellite 55 is the indispensable communications link that links the two stratospheric platforms together. There are no optical communication links between the stratospheric platforms 53 and 57 and there are no optically linked chains 24 of platforms (Fig. 1). , Further -there are no satellite bridges between optically linked chains 52 disposed in other parts

> ... I of the world. Telecommunications shunted through either GEO, MEO or LEO satellites are plagued by propagation losses and latency problems and in some cases because of their non- geostationary nature that are not present in high altitude platform communications due to the shorter distance for communications to travel between the ground gateway 30 and the high altitude gateway 28.

The invention (FIG. 4) in further optically linking the first high altitude gateway 28 with a second high altitude gateway 42 at a distance of about 500 to 700 km provides for a more reliable optical link as well as the high speed and highet volume of data that can be transferred between the high altitude platforms. The RF communications link between the ground gateway and the high altitude gateway in accordance With the novel communications frequencies and method also enables greater volumes of data to be transferred between ground gateway 30 and high altitude gateway 28., In the case of the use of a satellite 48 as illustrated in FIG. 1 the satellite either provides for redundancy or allows the bridging or linking of optically linked chains that are dispersed by long distances as illustrated in FIG. 1. The differences in the system and method of the invention will be recognized by reference to FIGs. 1, 2, 4-7 which compare the differences between available data rates and data rate losses assuming ail the same conditions including power and antenna size utilizing RF ground communications between GEO, MEO and LEO satellites as compared to the use of the high altitude gateways of the invention. Communications with satellites are generally in accordance with ITU-R (International Telecommunications Union Radio Bureau) Document 4-9S/17 which in Table I provides the following technical characteristics of proposed fixed service systems operating in the 37.0-57.2 GHz frequency band: TABLE I

In order to attempt to compare the advantages of the invention with atellite communications at the extremely high RF communications iink a 300 GHz frequency and a 0.5 meter antenna onboatd the novel high altitude platform, LEO, MEO and GEO satellites is compared in FIG. 2 and presented in detail in Table II.

TABLE II

RF Link Altitude Free Space Bit Rate Losses

High Altitude 20 km 168 dB 180 Gbps Platform

LEO 1,400 km 205 dB 180 Mbps

MEO 10>300 km 222 dB 3 Mbps

GEO 36,000 km 233 dB 250 Kbps

The calculation is based on the assumption that a bandwidth equaling 10% of the carrier frequency. is available for the system under consideration. Thus if the carrier frequency is 1 GΑz, then a 100 MHZ bandwidth is available. Similarly, if the carrier frequency is 100 GHz or 300 GHz, the bandwidths available are 10 GHz and 30 GHz respectively. In practice, the specttum below 50 GHz is vety crowded, hence the 10% assumption may not be valid.

The calculation also assumes that ah &F power of 1 Watt/100 Mbps is used for transmission. This is a very modest transmission power. Satellites typically use much higher power per bit rate, even though their top bit rates are very modest. The calculation takes into account both rain attenuation and atmospheric absorption in a region where the climate is relatively moderate (i.e., not too wet, and no too dry) . FlGs. 5, 6 and 7 graphically illustrate a comparison in bit rate per link with on board antenna of 2.5 meters, 1 meter and 0,75 meters respectively. These comparative example^'s demonstrate:

• 1. At the smallest -antenna aperture (75 cm) considered here, the top bit rate for the novel ^'■ high altitude system and method of the invention is around 180 Gbps per iink, so it will take just 6 gateway antennae to achieve the 1 Terabit rate at 300 GHz.₍ For satellite systems,^' the peak data rates are much lower.

The GEO system considered here could not even go past 1 Mbps. There is also little reason for the satellite systems to go beyond 50 GHz, since the gains in bit rate are quite minimal .

2. At somewhat larger antenna aperture (1 m), the novel high altitude system and method of the invention still has overwhelming advantage over the satellite systems. The LEO System is starting to show improvement achieving speeds of almost 10 Gbps.

• 3. At the largest antenna aperture (2_*5 m) considered, the gap between the novel high altitude system and method and the LEO system narrows but at the expense of bearing larger antenna apertures. The MEO system and GEO system are reaching speeds of 7 Gbps and 130

MbpS per link, respectively.

• 4. For satellite systems in general, there does not seem to be a need to go much beyond 50 GHz to achieve a higher bit rate.

5. For the novel high altitude system and method of the invention larger antenna apertures do not seem to improve the bit rate much.

^• 6. Beyond 500 GHz, the theoretically achievable data rate declines sharply for all systems. The latency (FIG. 2) in communication signals between ground station 70 and a high altitude platform gateway 28 in accordance with the invention are substantially smaller at 20 kilometers above the earth's surface than the losses between the ground station 70 and satellites. Specifically, the losses in communication from the ground station 70 to a LEO 72 is about 37 dB higher than the losses in communication from the ground Station 70 to a high altitude gateway, while the losses in communication from the ground station 70 to a MEO 74 are about 54 dB greater and a GEO 76 is about 65 dB greater, respectively. In addition losses in bit rate is negligible between the RF ground gateway and the high altitude gateway, ; whereas with the LEO it is 5 x 10^ while the bit rate loss with the MEO is 250 x 10³ while the bit rate loss with the GEO is 3 x 10^β.

As will be recognized by those skilled in the art radio frequency (RF) communications have been used for years for telephony and television broadcast systems* ' The limitations in bandwidth and data rates for point to point interactive links has limited access to a very small number of sites and thereby has limited access to only selected viewers. Among the reasons for limited broadband coverage are the relatively large footprints of satellite RF spot beams which prohibits efficient frequency reuse and the long time delays between an RF ground station 70 and a GEO 76. In addition, the individual links of a GEO 76 also have relatively low bit rates, except in the case where very large diameter antennae are used. This limitation of bit rate is due to a number of factors including the distance of the GEO 76 from the RF ground station 70 which greatly attenuates the signal strength of the communication. To compensate for such severe signal attenuation would dramatically increase the power requirements for RF

,1 transmissions from the^'RF ground station 70 to the GEO 76 as well as physical requirements such as increasing the antenna size for GEO 76 and RF ground station 70_*

Transmissions between a ground station 70 and a LEO 72 are further aggravated by the fast antenna tracking requirement since a LEO 72 is typically only visible for about 15-23 minutes per pass.

Similar ptoblems are encountered between transmissions between RF ground station 70 and MEO 74. The time delays between the RF ground station 70 and a MEO 74 are less than a GEO but still substantial. Communications between the ground Station 70 and the MEO 74 provide greater broadband capabilities, but once again the amount of data loss limits the amount_: of data rates.

Communications systems utilizing LEOs between a ground station 70 and a LEO 72 for the same power requirements and same antenna size result in an increase in the available bit rate for communications between RF ground station 70, LEO 72 to LEO and back to earth 20 as a result of the shorter distance between RF ground station 70 and LEO 72. However the resultant greater broadband capabilities of LEO is still insufficient to provide the data rates necessary for widespread Internet real time video and video telephone conferencing as will be required in the 21^st century. In contrast to the prior art limitations on bandwidth of about 50 GHz or less and maximum data rate transfers of a few gigabits per second for satellite communications and the expense of installing and maintaining terrestrial cable systems the invention provides a ground- based gateway 30 communicating with a high altitude gateway 28 in an RF frequency of 70 to 550 GHz and preferably in the range of 275 to 345 GHz. These extremely high frequencies not only result in a significant reduction in antenna size but also allow large data transfer rates without propagation losses and signal scattering through long distances of optical fiber cable systems.

The advantages of the invention are in part due to the discovery that specific attenuation due to rain above the 50 GHz can be overcome with the gain in directivity of the antenna as frequency increases. Another advantage of the invention is the recognition that adaptively reducing the bit rate while keeping the RF power constant can largely overcome the additional rain fade without introducing higher data error rate.

In addition the disadvantages due to attenuation due to heavy rains can be accommodated by providing a plurality of ground-based antenna gateways which are separated by at least a distance which is equivalent to the typical size of severe rain cells in a given geographic location. If heavy rain cells in a particular geographic location are separated by five to six kilometers then the plurality of antennae of for example two to five antennae can be separated in a triangular or circular pattern outside of the typical area of rain cells as illustrated in FIG. 10. The ground communications gateway can switch traffic among the various antennae to redirect more traffic toward an antenna located outside the area of severe rain in the local area without slowing down the Overall data traffic. Typically a separation of three antennae by about ten kilometers in a triangular pattern is sufficient to avoid the problem of specific attenuation due to rain.

Referring now to FIGs. 8 and 9, the specific attenuation due to rain is illustrated. In FIG. 8 the prior art graph indicates; an increase in specific attenuation due to rain increase with frequency at higher rain rates with greater attenuation with increases in frequency. FIG. 9 represents a graph baSed on calculations in accordance with the invention where a specific attenuation information can be obtained for a specific frequency without the necessity of relying upon exttapόlative tables or graphs_* ^' The significant advantage of the new calculation is that it can be performed using the formula as illustrated itt FIG. 9. As can be see from FIG. 9, at higher rain rates specific attenuation due to rain is only weakly^'.dependent upon frequencies greater than 50 GHz. At these higher frequencies rain attenuation is only slightly larger than for lower frequencies in the range of 50 to 70 GHz. The slight increase and attenuation due to rain is easily overcome by the significant increase in antenna gain which allows smaller antennae to be utilized on the high altitude gateways as well as their closer proximity to the earth. Specific attenuation due to rain for different climatic zones as well as excess attenuation due to atmospheric gases, ater vapor, mist, fog, o ygen and other gases can be accommodated in accordance with the invention by the utilization of multiple ground-based antennae separated by a distance sufficient to accommodate the local climatic conditions. Typically these climatic conditions can be accommodated virtually everywhere by the separation of ground-based gateway antennae by about two to fifteen kilometers . The higher frequency ranges employed in accordance with the invention of greater than 100 GHz up to.550 GHz allows a higher antenna gain which reduces the antenna array size necessary to support high speed high data communications between_; the ground gateway 30 and the high altitude gateway 28. The matching antenna sizes necessary for providing these very high frequency RF communications links for 100 GHz is an array size of about a 15 x 15 square meter (m²) array made Up of small dish antennae which are easily attached and borne by the high altitude gateway platform 28.

Within the array the relationship between antenna gain and frequenc for the same antenna size is related by the equation 20 log (f) (or about f² if in linear units) where f ^« frequency. This allows antennae of a relatively small size to provide high gain performance and this Way it permits the total payload antenna package to fit within the current carrying capability requirements fot high altitude platforms utilizing the advantages of the invention. As an example, when the frequency is 120 giga-Hertz and the antenna diameter as about 70 centimeters the antenna gain is 54.2 dBi while when the frequency is 274 giga-Hertz the diameter of the antenna can be decreased to a 30 centimeter diameter to provide the same antenna gain. Referring now to FIGs. 10, 11, 12 and 13 the advantages of the invention for replacing hardwired transcontinental and transoceanic cable communications systems is illustrated. Ground gateway 30 is Connected at one end to an inte faee 84 which connects existing telecommunications in the country or region to the ground gateway 30 which is connected to a plurality of ground antennae 32. Ground antennae 32 are separated by about two to twenty kilometers depending upon the size of heavy rain cells in the geographic area. Ground antennae 32 communicate RF signals with the high altitude gateway 28.

High altitude gateway 28 includes an RF optical converter 36 for converting RF signals into optical signals for transmission by laser 38 to one or more high altitude relay platforms 26 where N is any number of relay platforms necessary to optically link high altitude gateway 28 to high altitude gateway 42.

High altitude relay platform 26 includes a first laser 86 and a second laser 88 for receiving and transmitting optical signals between the first gateway platform and a second gateway platform 42. Alternatively each number N of relay platform 26 having a first laser 86 and a second laser 88 relays optical signals until the optical signals are received by second high altitude gateway 42. Second high altitude gateway 42 includes laser 40 and RF optical signal converter 36 which reconverts the optical signals back into extremely high radio frequency signals and transmits those signals back to a second ground gateway 46 through one of the antennae 32 based at a remote location. In the event one of the antennae 32 is covered by a large rain cell 90 any of the other antennae 32 outside of the heavy rain cell continues to receive and transmit without disruption of the communications signals between ground gateway 30 that for example is in America and ground gateway 46 that for example is in Europe. Second ground gateway 46 is similatly interfaced with an existing communications system 92 for a particular region or area.

High altitude relay platform 26 may be one or more relay platforms separated by a distance of from about 200 to 700 kilometers optically linked in a chain spanning the transoceanic or transcontinental area for which the novel high altitude telecommunications system serves. The first high altitude gateway 28 and second high altitude gateway 42 as well as the one or more high altitude relays.26 are high altitude aircraft capable of sustained deployment in the high tropopause or .stratosphere. The sustained deployment may be manned or unmanned aircraft that are sustained in a geostationary or geostatic position to maintain the communications link until substituted by a replacement high altitude platform. The area of deployment of the high altitude platform is in the high tropopause and stratosphere or is that part of the earth's high atmosphere that is above the Jetstream which is about 16 km as indicated in FIG. 2. Some references have incorrectly listed the Jetstream as extending to 15 - 25 km instead of the more accurate distance of 6 - 15 km above the earth's surface.

The high altitude relays or gateways are preferably long duration platforms or gateways that are unmanned. However it is possible also to utilize the novel system and method of the invention by utilizing manned high altitude aircraft, in either case the high altitude platform needs to maintain a geostationary or geostatic position within a radius of about 10 km as well as within an altitude of 3 km as illustrated in FIG. 13 to provide the high altitude gateway Or high altitude relay utilized in accordance with the invention.

The high altitude platforms used as high altitude relays and high altitude gateways may be aircraft of the lighter-than-air category, heavier-than-air or hybrid aircraft. Lighter-than-air aircraft include gas-filled balloons and dirigibles, heavier-than-air include aircraft generating lift by fixed or rotary wings and hybrid aircraft include those that include^" both a lifting gas as well as a fixed or rotary wing. Such aircraft preferably are unmanned and are capable of long duration of months or years in the high tropopause or stratosphere without the necessity of maintenance or replacement to achieve the advantages of the invention. Typical examples of high altitude platforms include manned and unmanned airships that may be high altitude airships that are lighter-than-air aircraft 94 (FIG. 12) an example of which is a Sky Station® platform of Sky Station International, Inc. An example of an unmanned heavier-than-air aircraft 96 is the Centurion of AeroViron ent and an example of a manned heavier-than-air aircraft 98 is the Proteus available from Angel Technologies Aircraft or a hybrid aitcraft 100 which includes propeller components 99 for maintaining lift and propulsion and which include lighter-than-air ballonets 101 to assist in lift and maintaining the aitcraft in a geostationary or geostatic position. The hybrid aircraft may include a tiltable propeller nacelle 103 for maintaining the airctaft in a geostatic position. These and other aircraft capable of maintaining a geostatic position in the uppet ttopopause or stratosphere are referred to as high altitude platforms, high altitude gateway or high altitude relay platforms. Referring now to FIGs. 10, 11, 12 and 13, the first high altitude gateway 28 and second high altitude gateway 42 preferably include an extremely high radio frequency transceiver capable of full duplex communications in the 100 to 500 giga-Hertz range and preferably in the range of 100 to 300 giga-Hertz for communicating with the ground-based gateway. The RF communications transceiver may be acquired from a number of manufacturers including TRW Inc., Space & Electronics Group, Redondo Beach, California, U.S.A. In addition to the RF communications assembly 102 (FIG. 15) an RF to optical to RF signal convettet 36 is utilized to convett and teconvert RF and optical signals. The RF and optical signal converter 36 may be obtained from Lucent Technologies, Murray Hill, New Jersey, U.S.A. The first and second high altitude gateways 28 and 42 may also include an ADD-DROP multiplexers 104 such as is available from Bookham Technology Ltd., Oxfordshire, U.K. The Optical signals from the RF and optical signal converter are transmitted to an optical transceiver which is connected to first optical laser 38. Optical transceiver 106 may be a number of available optical transceivers such as the Emissary 1400 SRSC optical transceiver or the

Emissary 1200 SRSC optical transceiver such as is available from Silk Road, Inc. of San Diego, California, U.S.A.

The optical transceivers are connected to optical lasers 38, 86 and 88 for receiving and transmitting optical signals to either the second high altitude gateway 28 or the high altitude relay 26 or the second high altitude gateway 42. Examples of lasers that can be used include the Model No. E2500-Type 2.5. Gbps Electroabsσrption Modulated Isolated Laser Module for ultra long reach applications, Model No. E2560/E2580-Type 10 Gbps EML Modules, Wavestar 40 Gbps all of which are available' from Lucent Technologies, Microelectronics Group, of Murray Hill, N.J., U.S.A. or the Model PGT 0401 or Model PGT 60310 both of which are available from Ericsson Microelectronics of Sweden. The high altitude gateways 28 and 42 available at both ends of the chain provide high communications high data links to the ground gateways utilizing bandwidths that allow the 1 Terabits per second throughput using the laser communications links between the high altitude gateways and optional relays. The optical lasers operate in wavelengths in the range of 1.3 - 1.5 microns (10^-6 meters) that provide sufficient bandwidth for supporting a 1 Terabit per second throughput in the ground to ground telecommunications system of the invention. Referring now to FlGs. 1, 14 and 19 the best mode of the invention is illustrated which utilizes a combination of ground gateway 30 and 46 connected to antennae 32 for communicating with a first high altitude gateway 28 and a second high altitude gateway 42 which are interlinked by a series of high altitude relays 26 to provide transoceanic, such as a transatlantic high altitude telecommunications system for replacing hardwired underwater cable systems. Bidirectional RF communication signals are converted in high altitude gateway 28 into optical signals that are transmitted by laser 38 to first high altitude relay 110. The first high altitude relay 110 optionally includes an ADD/DROP multiplexer for separating some of the low data rate optical communications from high data rate optical communications requiring real time bidirectional communications such aS video telephone and convetts only the low data rate optical signals into RF signals for transmission to satellite 64 . Satellite 64 transmits low data rate communications such as E-mail or low volume telephone communications directly to an RF receiver 112 in Europe. Alternatively satellite 64 can be used to provide for partial redundancy in the event of disruption in the optically linked high altitude platforms.

The high speed high data rate communications are transmitted through a free space optical link to high altitude relays 26, The last high altitude relay 26 in the straight chain 24 transmits the optical signals to high altitude relay 114 which includes an ADD/DROP multiplexer 104 which separates signals destined for England (FIG. 19) from signals destined,for continental Europe»^: Signals destined for England, ate convetted to RF signals by ADD/DROP multiplexer 104 and transmitted to third ground gateway 116 through antenna 32 while signals from England bound to the U.S. or to Europe are transmitted back to high altitude relay 114 for conversion into optical signals and transmitted bidirectionally to their U.S. or European destination.

One portion of the bidirectional optical signals in the Terabits per second rate are optically transmitted from high altitude relay 114 to relay 118 for optical transmission to second high altitude gateway 42. Relay 118 does not include ah RF! transceiver 102 or an RF optical converter 36 but merely an ADD/DROP ultiplexet 104 for separating optical signals bound to Germany and fourth ground gateway 120 from those bound to fifth ground gateway 122 in France and those bound to second high altitude gateway 42 and ground gateway 46 through relay platforms 26. In the best mode of the invention one or more of the high altitude relays 118 will include an ADD/DROP multiplexer 104 such as relay 124 for splitting the optical signal between the relays to allow a portion of the optical signals to be directed to two different destinations. A

. U N ,' ^{' • ■■ •} ..-' number of relays 11 (FIG. 19) include RF optical converter and RF communication' means 102 to communicate < with , ground gateway 116 as well. as a link 126 (FIG. 19) to satellite 64. The optically linked chain may also be multi-ended at both ends or one end (FIG. 14) where second high altitude gateway 42, third high altitude gateway 128 and fourth high altitude gateway 130 respectively provide RF links to ground gateways 46, 120 and 122 respectively. In this manner optical telecommunications signals can be separated in the high altitude platform for Specific destinations for particular regions of the earth and RF antennae can be provided for communicating with one or more specific ground gateways to interface with existing ground-based communications hubs or centers.

An optical communications signal link must be maintained between the first high altitude gateway 28 and the second high altitude gateway 42 as well as are intermediate high altitude relays 26. This optical link demands precision in the flight characteristics of the aircraft employed as high altitude platforms in the high tropopause and stratosphere. As indicated in FIG. 11 each high altitude gateway 28 and 42 as well as each high altitude relay can move about a pitch axis, a yaw axis and a roll axis.

In addition each high altitude platform can be out of alignment in the vertical axis or horizontal axis as represented by reference pitch axis 132 and yaw axis 134 or a combination thereof around the roll axis on relay 26 (FIG. 11) . These axis must be controlled by either the platform or the motor controlling the gimbaled laser to .within 3 degrees of any instantaneous deflection in any one direction in order to maintain the optical telecommunications link utilizing fast steering mirrors on each laser to maintain the optical communications link. The fast steering mirrors constantly make the adjustments within the 3 degree angle in any direction as long as the high altitude platforms are within the cylindtical areas of FIG. 13 as heretofore described. These 3 degree cortections are constantly made by the fast steering mirrors within a 359 degree arc around a 90 degree angle Of the center axis of the laSer beam of the gimbaled laser.

Referring to FIG. 11 and 13 the control of the pitch, yaw and roll axis in relation to the Center axis of the optical laser must be controlled within three (3) degrees of the vertical and horizontal position of each high altitude relay and- gateway platforms. The angular changes between relay 26 and gateway platforms 42 are illustrated where the angular change between laser 40 and laser 88 gradually move from alignment as represented b line 136 to positions of non alignment where relay 26 yaws to the right and the optical link is maintained by the fast steering mirror of relay 26 positioning laser 88 to the right and the fast steering mirrot of gateway positioning laser 40 to the left to maintain the optical link as represented by line 136.

When relay 26 also yaws to the left the optical link is similarly compensated for by the respective fast steering mirrors to move laser 40 to the left and laser 88 slightly to the right to maintain the laser link as represented by line 138. Changes in pitch, toll and altitude are similarly adjusted for by the fast steering mirror. Where rapid adjustment is required greater than 3 degrees a motor moves the entire assembly to allow the fast steering mirrors to again take over control for maintaining the laser link.

As will be recognized from FIG. 11 and 13 the first high altitude gateway, second high altitude gateway and intermediate relay platforms can experience changes in altitude and attitude due to variations in wind, navigation or other positional cltcumstances and still have the optical link between the platfotms maintained in accordance with the invention.

Referring now to FIGs. 11, 21 and 22 the angular variation between the high altitude gateway platforms 28 and 42 as well as the relay platforms 26 are accommodated by a fast steering mirror to control the optical link between lasers on different high altitude platforms by accommodating a 3 degree angular positional offset in any direction from the center axis of the laser by utilizing a motor 140 with a power supply and data source 142 for rotating the assembly around the x - axis as represented by arrow 14 to point a base 146 carrying a fast steering mirror 148 and a laser body^*150. Rotational movement around a y - axis is provided by a motor 152 to rotate base 146 around the y - axis as represented by artow 154.

Base 146 as illusttated in FIG. 22 includes fast steering mirror 148 to provide a small angular steering, of about 1 to 3 degrees sis represented by arrow 156_* This small angular steering provided by fast steerin mirror 148 allows laser body 150 to optically link with a: similar laser carried on a similar base having a fast steering mirror on either a relay or high altitude gateway platform. This precise pointing mechanism allows the gateway and relay platforms to maintain optical connection between each other over distance of about 700 kilometers as illustrated by FIG. 13.

Each laser body 150 provides a single wavelength channel which is combined to form a beam by means of lenses and mirrors to transmit bidirectional signals in a 1 Terabits per second tange to the interconnected optical links. Conventional wavelength multiplexing techniques such as dense wavelength division multiplexing can be used to provide high rates of speed and high transmissions of data over the optically linked lasers. Dense wavelength division multiplexing allows data to be encoded and decoded in a single transceiver system.

A combination of existing lenses and mirrors utilized in accordance with the invention can be obtained from Eastman Kodak Company, Commercial and Governmental Systems, Rochester, New York, U.S.A. as well as Ball Aerospace and Technologies Corporation of Boulder, Colorado, U.S.A. The fast steeting mirrors that can be utilized to move a light beam quickly, point the light beam to a particular direction and then stabilize it can be obtained from Ball Aerospace and Technologies Corporation of Boulder, Colorado, U.S.A.

The fast speed mirrors of Ball Aerospace and Technologies allow fot high bandwidth control, high accuracy beam steering, high quality optical surface and position accuracy within a small angular range of about 1 to 3 degrees. Due to the limited angular range of the fast speed mirror the motors 140 and 152 provide fast speed pointing of the lasers 150 particularly where the laser link is between a high altitude gateway or relay and a satellite. These motors allow a 90 degree travel from the axis of the laser beam to point to a Satellite where an alternate or redundancy is provide in accordance with the method and system of the invention.

Referring now to FIG. 16 and 20 a high altitude relay 26 is illustrated having diametrically opposed lasers 86 and 88 disposed on relay 26. Optical laser 86 is disposed in an optically clear nose or an optically clear area in nose 160 fo receiving and transmitting optical signals from either ariόther high altitude relay platform or a high altitude gateway platform. Optical lase 86 includes the laser body 150, motors 140 and 152 and fast steering mirrors 148 as heretofore discussed for pointing the laser within the 3 degree angular limits to provide an optical link between the relay or gateway platform. In addition high speed motor 140 is provided for moving laser 150 around the x - axis 140 to allow the laser to be pointed straight up 90 degrees from the axis of the laser to provide a laser communication link with a satellite having optical communications capability to provide additional advantages of the invention as heretofore discussed. Laset 88 containing the same components as laser 86 is diametrically opposed from laser 8 and is supported by a ftame assembly 162 for supporting laser 88 in an optically clear pod 164 for communicating with a similar laser disposed in either a high altitude relay or high altitude gateway platform. Lasers 86 and 88 are interconnected via a fiberoptic cable 170 that may be disposed within the inside of the high altitude relay 26 (FIG* 20) .

Fiberoptic cable 170 may include a passive amplification meanS 172 or an optical regenerator 174 or both a passive amplification means and a regenerative repeater or optical regenerator. The length of fiberoptic cable 170 is limited to the distance between the lasers on the high altitude platform and preferably includes passive amplifiers. All optical transmitters and receivers are in pairs such as diamettically opposed lasers 86 and 88 and preferably include passive amplifiers 172. Passive amplifiers such as, aman amplifiers, Brillorin amplifiers and Erbium doped fiber amplifiers (EDFA) can be utilized in accordance with the preferred embodiment of the invention. In applications where Optical distortion of signals is a problem a regenerative repeater or optical regenerator 174 should be employed. ^■.; Regenerative repeaters may be obtained from Lucent Technologies, Inc. of Murray Hill, N.J., U.S.A. or Nortel Networks i Corporation of Brampton, Ontario, Canada. Referring, noW to FIG. 17 and 18 additional high altitude relays and gateways in accordance with'alternative embodiments of the^' invention are illustrated. In FIG. 17 a high altitude relay* platform 26 is illustrated having an antenna 176 for receiving and transmitting RF signals to a satellite as has heretofore been described, in. FIG. 17 a portion of the low data rate communications such as E-mail are divided from high data rate real time bidirectional communications such as video conferencing. The high volume high data rate communications optical signals are transmitted by laser 88 to a high altitude relay or gateway platform. The low data rate low speed signals are converted into RF signals that are transmitted to either a LEO, GEO or MEO satellites via links 180, 182 and 184. Radio ftequency signals that represent low data rate low bit rate communications such as E-mail are sent via an RF communications link 180 to a GEO satellite that due to the limitations of the GEO is only able to receive and transmit signals at a data rate of from about 1_*5 Mbps to 155 Mbps. Another portion of the RF signals are transmitted to a MEO satellite via, an RF link 182 where the limitations of the MEO allow it to receive and transmit signals at a data rate of from about 155 Mbps to 1.26 GbpS. A third portion of the RF signals are transmitted and received from a LEO satellite via an RF link 184 where due to the limitations of the MEO a data rate of from about 155 Mbps to 2.4 Gbps can be transmitted for purposes of redundancy, chain linking or direct RF links to the ground as has heretofore been desdribed. As heretofore described the optical laser 86 and

88 should be disposed in diametrically opposed positions on the high altitude' platform. As indicated in FIGs. 18 and 20 these diametrically opposed positions are on the nose and on the tail. In FIGs* -18 and 20 the optical lasers 186 and 188 are disposed in insttUment pods 190 and 192 respectively for the bidirectional communication of signals 194 and 196 respectively. Lasers 186 and 188 may receive signals from ADD/DROP multiplexer 104 to communicate laser signals from platform 118 (FIG. 14) between France and Germany as has heretofore been described.

The method of the invention provides high data rate and high speed communication between two points on the earth for replacing existing cable and hardwired telephone services. The alternative high altitude optical telecommunications^' method and system of the invention provides extremely high data rate, high speed communications by linking a ground-ba ed gateway having an RF transceiver with a first high altitude gateway deployed in the upper tropopause or in the Stratosphere. The first high altitude gateway includes an RF transceiver and a means for converting the RF signals into optical signals and a laser for the bidirectional communication of those optical signals to one or more relay platforms and to a high altitude gateway platform for Subsequent reconversion of the optical signals into RF signals and the transmission of those RF signals down to a ground gateway.

The method of the invention provides for the use of frequencies at ot above 100 giga-Hertz to assure the broad bandwidth necessary to make the optical communications link effective in transmitting at least 1 Terabits per second of signals between the optical lasers to provide a high speed, high data rate bidirectional communications system between lasers using the stratosphere or high tropopause as the transmission medium. The stratosphere and high tropopause as a transmission medium is substantially free of moisture, Clouds, fog or other gases that would have a deleterious effect on the telecommunications system. The method of the invention provides for the maintaining of the high altitude platform in a geostationary position to allow alignment of lasers using about two degree of freedom gimbals and fast steering mirrors to establish laser communications links between relays in the optically linked chains .

The method oi the invention provides for the use of ADD/DROP multiplexers to divide a portion of the communications to two different high altitude gateways or to two different relays in the optically linked chain. The method further provides for the use of optical and RF signal converters in one or more of the relays to convert a portion of the optical signals- to RF signals to allow that portion of the signals to be transmitted to the ground. The method of the invention provides for end to end chains or end to multi-end chains or multi-end chains to multi-end to replace existing transoceanic and transcontinental hardwired cable systems.

The system and method of the invention provides for the utilization of satellite links, either optical or RF links, to provide redundancy or, for purposes of dividing a portion of the telecommunications signals between optically linked chains or divettlng a portion of the low data rate, low volume or low peed portion of the telecommunication signals to LEO, GEO or MEO satellites for subsequent transmission to the ground.

The invention provides for the utilization of a combination of high altitude relays and gateways for replacing existing hardwired cable telephone systems and interconnection by providing an alternative telecommunications path. The alternative telecommunications paths in the form of chains which mimic the use of cable and fiberoptic hardwired cable systems currently in use provide an additional advantage over prior art telecommunications hardwired cables in that chain skipping utilizing satellites can be utilized in accόtdance with the invention. As such the method and system of the invention contemplates the use of satellites for linking one or more chains together that are disposed at great distances from one another around the surface of the earth.

^■ The novel high altitude optical telecommunications system of method o the invention as will be recognized by those skilled in the art is susceptible to a wide range of changes and modifications suitable for particular applications utilizing the high altitude gateways and high altitude relays in combination with the ground relay stations for providing a wide range of telecommunications options in replacing existing hardwired cable Systems. The high altitude relays and gateways can be configured in a variety of ways utilizing various high altitude aircraft of varying designs to operate as a high altitude gateway or relay in accordance with the invention.

The high altitude airborne vehicles may be modified in a variety of ways to accomplish the advantages of the invention in providing stratospheric and high tropopause telecommunications links and relays. These and other methods for implementing the invention are to be construed within the scope of the claims in referring to a high altitude platform as long as the high altitude platform is capable of maintaining a geostationary position within an altitude of about 1 km (.62 mi) to 3 km (1.9 mi).

As will also be recognized the high altitude optical telecommunications system and.method of the invention may be modified in a number of ways to provide varying degrees of branches at one end or both ends of the telecommunications optically linked cable to interface with existing ground systems. These optically and RF linked systems may be provided in a number of ways utilizing lasers and RF communications gateways and transceivers in a manner known by those skilled in the art to provide the advantages of the invention.

As will be recognized the invention may be implemented in a number of ways to provide chain skipping capabilities between various optically linked chains of the invention utilizing either LEO, GEO or MEO satellites. In addition one or more relays may be utilized to bridge chains to achieve the advantages of the invention. These and other methods for implementing the invention may be readily accomplished by those skilled in the art and are to be deemed to be included in the present claims.

As used herein and in the following claims, the word ^comprising' or ^comprises' is used in its technical sense to mean the enumerated elements include but do not exclude additional elements which may or may not be specifically included in the dependent claims. It will be understood such additions, whether or not included in the dependent claims, ate modifications that both can be made within the scope of the invention. It will be appreciated by those skilled in the art that a wide range of changes and modification can be made to the invention without departing from the spirit and scope of the invention as defined in the following claims:

Claims

WHAT IS CLAIMED IS:

1. A ground to ground communications system comprising: (a) a first ground-based gateway having a means for communicating F signals; (b) a first high altitude platform having a means for communicating. F, signals, a means for converting RF signals and optical j signals and a laser means for communicating optical Signals; (c) a second high altitude platform having a laser means for communicating optical signals/ a means for converting optical signals and RF signals and means for communicating RF signals; and (d) a seco d ground-based gateway remote from said first ground-based gateway having means for communicating RF signals.

2. The ground to ground communications system of claim 1 wherein said laser means for communicating signals on said first high altitude platform is directed by a fast steering mirror.

3. The ground to ground communications system of claim 1 further comprising a relay high altitude platform disposed intermediate said first high altitude platform and said second high altitude platform having a laser for communicating optical signals.

4. The gtound to gtound communications system of claim 1 wherein said first high altitude platform includes an ADD-DROP multiplexer_*

5. The ground to ground communications system of claim 3 wherein said telay high altitude platform includes an ADD-DROP multiplexer.

6. The ground to ground communications system of claim 5 wherein said relay high altitude platform includes means* for communicating RF signals.

7. The ground to ground communications system of claim 5 wherein said first high altitude platform includes an ADD-DROP multiplexer.

8. The ground to ground communications system of claim 7 wherein said second high altitude platform includes an ADD-DROP multiplexer.

9. The ground to ground communications system of claim 3 wherein. said first high altitude platform includes means for communicating signals to a satellite.

10. The ground to ground communications system of claim 9 wherein said relay high altitude platform includes means for communicating signals to a satellite.

11. The ground to ground communications system of claim 10 wherein said second high altitude platform includes means for communicating signals to a satellite_*

12. The ground to ground communications system of claim 9 wherein said satellite includes means for communicating with a second ground to ground communications system.

13. The ground to ground communications system of claim 3 wherein each of said means for communicating RF signals is an RF transceiver.

14. The gtound to ground communications system of claim 13 wherein said RF transceiver provides an RF bidirectional link carrying at least one Terabits of data per second.

15. The ground to ground communications system of claim 13 wherein each of said laser means for communicating optical signals is an optical laser transceiver.

16. The groUnd to ground communications system of claim 15 wherein said optical laser transceiver provides an optical bidirectional link capable of carrying about one Gigabit to 1,000 Terabits of data per second.

17. The ground to ground communications system of claim 16 wherein said optical bidirectional link utilizes a dense wavelength-division multiplexer.

18. The ground to ground communications system of claim 15 wherein each optical laser transcelvet communicates in a wavelength in the 'tange of about 1.3 to 1.5 microns (10" ⁶m).

19. The ground to ground communications system of claim 14 wherein each RF transceiver transmits in a high frequency range of greater than 70 GHz (giga-Hertz) .

20. The ground to ground communications system of claim 19 wherein each RF transceiver transmits in a high frequency range of greater than 270 GHz (giga-Hertz) .

21. The ground to ground communications system of claim 1 wherein said first ground-based gateway is a plurality of antennae for communicating RF signals separated by about 10 km (kilometers) on the ground.

22. The ground to ground communications system of claim 1 wherein said first high altitude platform is a high altitude aircraft.

23. The ground to ground communications system of claim 1 wherein said first high altitude platform is a high altitude airplane

24. The ground to ground communications system of claim 1 wherein said first high altitude platform is a high altitude hybrid aircraft.

25. The grόUnd to ground communications system of claim 1 further comprising a plurality of relay high altitude platforms; each having a laser for communicating optical signals disposed intermediate said first high altitude platform and /said second high altitude platform.

26. The ground to ground communications system of claim 25 wherein at least one of said plurality of relay high altitude platforms includes an optical signal regenerator.

27. The ground to ground communications system of claim 25 wherein at least one of said plurality of relay high altitude platforms includes an optical amplifier.

28. The ground to ground communications system of claim 25 wherein each laser is gimbaled to provide about a 359 degrees of travel in any direction.

29. The ground to ground communications system of claim 26 wherein each laser fot communicating optical signals includes a. fast steering mirror.

30. The ground to ground communications system of claim 28 wherein each laser for communicating optical signals includes means for providing a 90 degree travel from the center axis of beam of said laser.

31. The ground to ground communications system of claim 25 wherein said first high altitude platform includes means for the duplex communications of signals to a satellite.

32. The ground to ground communications system of claim 31 wherein at least one of said plurality Of relay high altitude platfόritts includes means for the duplex communications Of Signals to a satellite.

33. The ground to ground communication system of claim 32 wherein said. satellite includes means for communicating with a second ground to ground communications system.

34. The ground to ground communications system of claim 33 wherein said satellite includes means for communicating with a third high altitude platform having a laser means for communicating optical signals, a means for converting optical signals and means for communicating RF signals.

35. The ground to ground communications system of claim 34 wherein said .third high altitude platform j communicates with a third ground-based gateway remote from said first ground-based gateway and said second ground-based gateway.

36. The ground to ground communications system of claim 25 wherein at least one of said plurality of relay high altitude platforms includes an ADD-DROP multiplexer.

37. The ground to ground communications system of claim 36 wherein said ADD-DROP multiplexer communicates with a third high altitude platform having laser Beahs for communicating optical signals, a means for converting optical signals and a means for communicating RF signals.

38. The ground to ground communications system of claim 37 wherein said third high altitude platform communicates with a third ground-based gateway remote from said first ground-based gateway and said second ground-based gateway.

39. The ground to ground communications system of claim 36 wherein said at least one of said plurality of relay high altitude platforms includes a means for converting RF signals and optical signals and means for communicating RF signals_*

40. The ground to ground communications system of claim 39 wherein said at least one of said plurality of relay high altitude' platforms communicates RF signals with a third ground-based gateway remote from said first ground- based gateway and said second ground-based gateway.

41. A high data and speed communications system comprising: (a) . a ground-based gateway having a transceiver for communicating signals in a hig frequency range of at least 70 GHz; (b) a high altitude communications gateway having a transceiver for communicating signals ith said ground-based gateway, a means for converting signals in a high frequency range of at least 70 GHz into optical signals and an optical laser transceiver for communicating optical signals to a second high altitude platform; (c) a fast steering mirror for steering said optical laser transceiver; and (d) an RF reception antenna disposed on said high altitude communications gateway having an antenna array for communicating ith said ground-based gateway.

42. The high data and speed communications system of claim 41 further comprising an ADD-DROP multiplexer disposed in said high altitude communications gateway.

43. The high data and speed commuriications system of claim 41 further comprising a dense wavelength division multiplexer disposed in said high altitude communications gateway.

44. The high data and speed communications system of claim 41 further comprising a plurality of ground-based antennae for communicating signals to said high altitude communications gateway in a high frequency range of at least 70 GHz separated by a distance greater than the size of heavy rain cells in the geographic area.

45. The high data and speed communications system of claim 41 further comprising mechanical means for articulating said optical laser to provide a 90 degree angular travel in any direction from the center axis of the laser beam.

46. The high data and speed communications system of claim 45 wherein about 3 degrees of said 90 degree angular travel in any direction is controlled by said fast steering mirror.

47. The high data and speed communications system of claim 45 wherein said optical laser includes a high speed motor for providing said angular travel for said optical laser.

48. The high data and speed communications system of claim 41 wherein said high altitude communications gateway is a lighter-than-air aircraft.

49. The high data and speed communications system of claim 48 wherein said ground-based gateway and said RF reception antenna disposed on said high altitude communications gateway allows the use of the same frequency to transmit and receive an RF signal.

50. The high data and speed communications system of claim 48 wherein said high frequency range is about 120 GHz or greater and said RF reception antenna is about 1 meter in diameter or less.

51. The high data and speed communications system of claim 50 wherein said high frequency range is about 274 GHz or greater and said RF reception antenna is about 1 meter in diameter or less.

52. A communications system comprising: (a) a first ground-based gateway having a transceiver for communicating RF signals; (b) a first high altitude gateway having a transceiver for communicating RF signals with said first ground-based gateway, a converter for the conversion of RF signals and optical signals and a laser for transmitting and receiving signals; , (c) a second high altitude gateway having a laser for transmitting and receiving signals, converter for the conversion of RF signals and optical signals and a transceiver for communicating RF signals to a second ground- based gateway; and (d) a second ground-based gateway having a transceiver for communicating RF signals with Said second high altitude gateway,.

53. ^~ The communications system of claim 52 further comprising a relay high altitude platform disposed intermediate said first high altitude gateway and said second high altitude gateway having a laser for communicating optical signals.

54. The end to end Communications system of claim 53 wherein said relay high altitude platform includes a plurality of relay high altitude platforms disposed intermediate said fitst high altitude gateway and said second high altitude gateway.

55. The communications system of claim 54 wherein at least one of said plurality of relay high altitude platforms includes an,ADD-DROP multiplexer.

56. The communications system of claim 55 wherein each of said plurality of relay high altitude platforms are maintained substantially in vertical and horizontal alignment.

57. The^' communications system of claim 55 wherein said ADD-DROP multiplexer communicates with said plurality of relay high altitude platforms and with a third high altitude platform having a laser for transmitting and receiving signals.;,

58. The comm nications system of claim 56 wherein said third high altitude platform communicates with a third ground-based gateway remote from said first ground-based gateway and said second ground-based gateway.

59. The communications system of claim 56 wherein said third high altitude platform includes a converter for the conversion of RF Signals and optical signals and a transceiver for communicating RF signals.

60. The communications system of claim 59 wherein said third high altitude platform includes a converter for the conversion of RF signals and optical signals and communicates RF signals with said third ground-based gateway providing a bidirectional link for carrying about one Terabits of data per Second.

61. The communications system of claim' 53 wherein said laser in said first high altitude platform and said laser in said second high altitude platform and said laser in said relay high altitude platform are optical laser transceivers providirig an optical bidirectional link for carrying about one Terabits of data per second.

62. The communications system of claim 61 wherein said optical bidirectional link utilizes a denSe wavelength- division multiplexer.

63. The communications system of claim 53 wherein said transceiver in said first gateway and said transceiver in said second gateway and said transceiver in said first high altitude gateway and said transceiver in said second high altitude gateway transmit in a very high ftequency range of greater than 70 GHz (giga-Hertz).

64. The communications system of claim 61 wherein said transceiver in:said first ground-based gateway and said transceiver in said Second ground-based gateWay and said transceiver in said first high altitude gateway and said transceiver in said second high altitude gateway transmit in a very high frequency range of greater than 270 GHz (giga- Hertz) .

65_* The communications system of claim 52 wherein said first high altitiide gateway is a lighter-than-air aircraft.

66. The. communications system of claim 65 wherein said second high altitude gateway is a high altitude aircraft.

67. The communications system of claim 66 wherein said first high altitude gateway is a hybrid aircraft.

68. The communications system of claim 65 further comprising a relay high altitude platform having a first laser and a second laser.

69. The communications system of claim 68 wherein said first laser and said second laser are mounted in a first instrument pod and a second instrument pod.

70_* The • communications system of claim 69 wherein said first laser mounted in said first instrument pod and said second laser mounted in said second instrument pod are disposed on diametrically opposed surfaces of Said relay high altitude platform.

71. The communications system of claim 70 wherein said laser mounted in Said first instrument pod and said second laser mounted in said second instrument pod communicate through an optical fiber.

72. The communications system of claim 71 wherein said laser mounted to said instrument pod and said second laser appended from said second instrument pod are each gimbaled to provide a two axis angular positional travel in any direction.

73. The communications system of claim 70 wherein said first laser mounted in said first instrument pod includes means for^' communicating with a satellite.

74. The communications system of claim 68 wherein said first laser is mounted in the nose of said relay high altitude platform..

75. The communications system of claim 74 wherein said second laser Is mounted in the tail of said relay high altitude platform.^"

76. The communications system of claim 75 wherein said first laser mounted in said nose and said Second laser mounted in said tail are gimbaled to provide a two axis angular travel in any direction.

77. The communications system of claim 75 wherein said relay high altitude platform includes a third laser mounted to the top surface of said relay high altitude platform for communicating with a third high altitude platform.

78. A method for providing high bandwidth high speed communications comprising: (a) ' deploying a first high altitude platform containing an RF ttansceiver and a means for converting RF signals and optical signals and a first laser for communicating optical signals; (b) establishing an RF ground-based gateway having an RF transceiver means for communicating with said RF transceiver meahs in said first high altitude platform; and (c) maintaining said first high altitude platform in a geostationary position to allow said first laser to align with a Second laser disposed in a. second high altitude platform to establish an optical communications link.

79. The method of claim 78 further comprising the step of utilizing a fast steering mirror to allow said first laser to align with said second laser.

80. The method of claim 78 further comprising the step of deploying a second high altitude platform containing an RF transceiver and a means for converting RF signals and optical signals with said second laser.

81. The method of claim 80 further comprising the step of establishing a second RF ground-based gateway having an RF transceiver means for communicating with said second RF transceiver in said Second high altitude platform.

82. The method of claim 81 further comprising the step of deploying a relay high altitude platform having an optical laser disposed intermediate said first high altitude platform and said second high altitude platform^".

83. The method of claim 82 further comprising the step of providing a satellite laser for communicating with a satellite on said first high altitude platform.

84. The method of claim 78 further comprising the step of providing a communications link with a satellite.

85. The method of claim 84 wherein said step of providing a communications link with a satellite is used for redundancy.

86. The method of claim 84 wherein said communications link with a satellite is used for a low data rate communications¹ portion of the telecommunications signals.

87. The method of claim 86 wherein said low data rate communications portion is E-mail.

88. The method of claim 82 further comprising the step of deploying a third high altitude platform containing an RF transceiver and means for converting RF signals and optical signals and a third laser disposed ort said third high altitude platform;

89. The_: method of claim 88 further comprising the step of establishing a _: third RF ground-based gateway having an RF transceiver for ' communicating with said RF transceiver disposed in said thitd high altitude platform_*

90. The method of claim 89 further comprising the step of providing a communications link with a relay high altitude platform to switch a second portion of the communications signals to said relay high altitude platform.

91. The method of claim 90 wherein said second portion of the communications signals are transmitted from said relay high altitude platform to said third high altitude platform.

92. The method of claim 91 further comprising the step of dividing a portion of the communications signals into a third portion of communications signals.

93. The method of claim 92 wherein said third portion of the commnications signals are converted to RF signals and transmitted to a fourth ground-based gateway.

94. A high data high volume communications system comprising: (a) a first ground-based gateway for communicating RF signals at a frequency of about 70 GHz or greater; (b) a first high altitude gateway having means for converting said RF signals at a frequency of about 70 GHz or greater into optical signals carrying: bidirectional data Signals at a rate of about the 1 Terabits per second range and a laser for transmitting and receiving said bidirectional data signals; (c) ^'; a second high altitude gateway having means for converting RF signals at a frequency of about 70 GHz or greater into optical signals carrying bidirectional data signals at a rate of about the 1 Terabits per second range and a laser for transmitting and receiving said bidirectional data signals; and (d) a Second ground-based gateway remote from said first ground-based gateway for communicating RF signals at a frequency of about 70 GHz or greater to said second high altitude gateway. :^! :•^■

95. The high data high volume communications system of claim 94 futther comprising a relay high altitude platform disposed intermediate said first high altitude gateway and said second high altitude gateway having a laser for receiving and transmitting said bidirectional data signals in about the 1 Terabits per second range.

96. A high altitude telecommunications platform comprising: ^:' :: ^! (a) an outside housing for maintaining the telecommunications, platform in the upper tropopause or stratosphere; (b) an optically clear laser housing disposed on said outside housing; (c) a laser disposed inside said optically clear laser housing; ^" and (d) a, fast steering mirror fot pointing said laser.

97. The high altitude telecommunications platform of claim 96 wherein said telecommunications platform is a lighter-than-air aircraft.

98. The high altitude telecommunications platform of claim 96 further comprising a system of solar cells for converting sunlight, into electrical energy for operating said telecommunications platform.

99. The high altitude telecommunications platform of claim 96 wherein said telecommunications platform is an aircraft.

100. The high altitude telecommunications platform of claim 96 wherein said telecommunications platform is a hybrid aircraft_*

101. The high altitude telecommunications platform of claim 96 wherein said telecommunications platform includes a GPS (global positioning satellite) receiver to maintain said telecommunications platform in an area of the upper tropopause or stratosphere.

102. The high altitude telecommunications platform of claim 96 wherein said fast steering mirror is disposed in a gimbaled housing.

103. The high altitude telecommunications platform of claim 102 wherein said gimbaled housing includes a first motor for controlling the degree of travel along the x - axis and a second motor for controlling the degree of travel along the y - axis.

104. The high altitude telecommunications platform of claim 103 wherein said first motor and said second motor control the degree of travel along the x - axis and the y - axis outside of the angular control provided by said fast steering mirror.