WO2000027773A1 - Methods and apparatus for producing optical fiber - Google Patents
Methods and apparatus for producing optical fiber Download PDFInfo
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- WO2000027773A1 WO2000027773A1 PCT/US1999/019139 US9919139W WO0027773A1 WO 2000027773 A1 WO2000027773 A1 WO 2000027773A1 US 9919139 W US9919139 W US 9919139W WO 0027773 A1 WO0027773 A1 WO 0027773A1
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- tube
- core
- feedstock
- fiber
- optical fiber
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Classifications
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
- C03B37/02709—Polarisation maintaining fibres, e.g. PM, PANDA, bi-refringent optical fibres
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
- C03B37/01217—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube for making preforms of polarisation-maintaining optical fibres
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
- C03B37/0122—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube for making preforms of photonic crystal, microstructured or holey optical fibres
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/026—Drawing fibres reinforced with a metal wire or with other non-glass material
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
- C03B37/02736—Means for supporting, rotating or feeding the tubes, rods, fibres or filaments to be drawn, e.g. fibre draw towers, preform alignment, butt-joining preforms or dummy parts during feeding
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
- C03B37/02754—Solid fibres drawn from hollow preforms
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
- C03B37/0279—Photonic crystal fibres or microstructured optical fibres other than holey optical fibres
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/34—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with rare earth metals, i.e. with Sc, Y or lanthanides, e.g. for laser-amplifiers
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/34—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with rare earth metals, i.e. with Sc, Y or lanthanides, e.g. for laser-amplifiers
- C03B2201/36—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with rare earth metals, i.e. with Sc, Y or lanthanides, e.g. for laser-amplifiers doped with rare earth metals and aluminium, e.g. Er-Al co-doped
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/54—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with beryllium, magnesium or alkaline earth metals
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/58—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with metals in non-oxide form, e.g. CdSe
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2203/00—Fibre product details, e.g. structure, shape
- C03B2203/42—Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres
Definitions
- the present invention relates generally to improvements in optical fiber waveguides and their manufacture. More particularly, the present invention relates to novel methods and apparatus for forming optical fiber waveguides via filament in tube and stick in tube methods of fiberization.
- Optical fiber waveguides have come to play an increasingly important role in communications.
- a range of optical fiber types with regard to size, index profiles, operating wavelengths, materials, etc., must be available in order to fulfill many different system applications.
- active devices such as amplifiers, lasers, switches and dispersion compensators.
- optical fiber cables must be spliced together without excessive practical difficulties. It is important that these splicing techniques may be applied with ease in field locations where cable connection takes place. It is particularly important in many applications that a new fiber may be readily spliced to an existing fiber already in place. Put otherwise, removing all the existing fiber and replacing it with new fiber having different characteristics is often not an option.
- Another method involves the insertion of a core material into a molten cladding material to create a preform.
- the core insertion is performed rapidly so that the core does not soften or dissolve during the procedure.
- the resultant preform is then drawn into optical fiber.
- Flouhde glasses, such as ZBLAN, manufactured in this fashion are not fusion spliceable to silica fibers, are prone to devitrification and have poor durability.
- One of the more important methods employed in making soot used in the manufacture of low loss optical fiber is the chemical vapor deposition (CVD) process.
- CVD chemical vapor deposition
- relatively pure chemicals such as silicon tetrachloride
- MCVD process is also a known CVD process.
- a core cullet feedstock (having a particle size typically in the range of 100 - 5,000 urn) is introduced into a cladding structure.
- the end of the core/cladding structure is heated in a furnace to near the softening temperature of the cladding and drawn into optical fiber.
- This method overcomes some of the disadvantages of typical CVD processes, allowing the cladding composition to consist of pure Si0 and the core composition to consist of multicomponent glasses.
- the present invention also relates to an optical fiber having a numerical aperture greater than about .35.
- Such fibers which comprise a core and clad region which are glass, and are doped with a rare earth element which is selected from the group consisting of ytterbium, neodymium, and erbium, can be used to fiber lasers.
- Such fiber lasers can be made by coupling a pump source coupled to the high NA fiber.
- numerical apertures of about .40 or greater e.g. .45
- the present invention provides methods and apparatus for producing a wide variety of optical fibers via filament in tube or stick in tube methods of fibe zation.
- the present invention comprises the steps of filling a glass tube with a glass filament or stick of the desired material and subsequent drawing or elongation of the glass tube at elevated temperatures.
- the material within the tube melts at the draw temperature and fills the tube to form a continuous core.
- the loose fitting feedstock can be automatically fed or melted down by gravity to maintain a constant depth of molten feedstock, yielding a homogeneous and reproducible product.
- the feedstock can be comprised of a core material or a core/clad material.
- the tube can be comprised of additional core material (e.g., which could be used to form the outer core region), core/clad material, or a cladding material.
- additional core material e.g., which could be used to form the outer core region
- core/clad material e.g., a cladding material
- the present invention can be used to draw optical fiber directly (filament in tube) or can be used to make a core cane or a core clad cane which is then overcladded with additional material before being drawn into optical fiber (stick in tube).
- the present invention allows almost any glass that can be produced by chemical (sol-gel, vapor deposition, etc.) or physical (batch and melt) techniques to be economically fabricated in the form of a continuous clad filament.
- chemical sol-gel, vapor deposition, etc.
- physical batch and melt
- FIG. 1 is a cross sectional drawing of suitable apparatus for performing the filament in tube method of drawing optical fiber in accordance with the present invention
- FIG. 2 is a cross sectional drawing of suitable apparatus for performing the stick in tube method of drawing optical fiber in accordance with the present invention
- FIG. 3 illustrates suitable apparatus for overcladding an optical cane formed in accordance with the present invention which may then be drawn into optical fiber in accordance with the present invention
- FIG. 4 is a graph showing loss as a function of wavelength for a 5 meter span of optical fiber produced in accordance with a filament-in-tube method of the present invention
- FIG. 5 is a graph showing the refractive index profile of a core clad cane produced in accordance with the present invention
- FIG. 6 is a graph showing loss as a function of wavelength for a 5 meter span of optical fiber produced in accordance with a stick-in-tube-method of the present invention.
- FIG. 7 is a graph showing the loss and mode field diameter as a function of fiber length for an optical fiber produced in accordance with the present invention.
- the present invention provides methods and apparatus for producing a wide variety of optical fibers via filament in tube and stick in tube methods of fiberization as more fully discussed below.
- a glass or crystalline stick of the desired core composition should be obtained. It does not matter if the stick has a round, square, or triangular, or some other different cross section, it need only fit within a cladding tube with which it is to be utilized. Unlike the well known rod-in-tube method, the inventive method does not require the core to fit tightly and concentrically within the cladding tube, since the core filament melts to conform to the cladding walls.
- the tube bore need not be circular, but can be of a rectangular, elliptical, or other non-circular shape to enable formation of a fiber having a non-circular core.
- the core glass or stick conforms to the shapes of the internal diameter of the tube, when a rectangular shaped tube bore is employed, the core glass will deform to the shape of the tube, thereby forming a core region upon solidification which is rectangular in shape.
- a fiber having a generally rectangular core can be made by employing a tube having a rectangular shaped inside diameter. After drawing of the fiber, the core remains of a substantially rectangular shape in cross-section (with some rounding of the corners of the rectangle).
- Fibers having a rectangular shaped core have been made, using the methods of the present invention disclosed herein, which exhibited a numerical aperture (NA) of greater than about .35, in particular we have achieved numerical apertures of about .45.
- NA numerical aperture
- Such high NA fibers cannot generally be made using CVD techniques, because the large amount of modifier needed for such refractive index changes causes crystallization, cracking, or sagging of the core material during manufacture.
- Such a fiber having rectangular shaped core can be used for efficiently coupling the light from a stripe laser diode. For instance, a typical high powered stripe laser diode emits a beam having essentially a 100 ⁇ m x 1 ⁇ m rectangular geometry.
- a beam having this geometry is more efficiently captured by a fiber formed in accordance with the present invention to have a substantially similar core geometry to that of the laser beam.
- non-circular shaped tube bores could also be employed, including elliptical, which could be employed to form polarization maintaining fibers.
- tubes having an outer periphery that is non-circular in cross-section can also be utilized, to manufacture fibers whose outer periphery is non- circular.
- high drawing viscosity is preferable to facilitate the fiber or core cane at least substantially retaining the shape of the ID or OD, or both.
- the draw rate and temperature of the preform is maintained so that the resultant fiber or core cane at least substantially retains the shape of the inside and outside of the tube.
- the inventive method also does not require the core stick to be uniform in cross section and have a smooth surface, unlike prior rod-in-tube technology.
- the core stick can be fabricated by conventional crucible melting and casting, drawing, sol-gel, or some other technique. The stick is then loaded into the cladding tube.
- the composition of the tube which becomes the fiber cladding is not limited and can range from pure SiO 2 to multicomponent glasses. The only requirement is that the core glass melt at or below the softening point of the cladding tube and that the thermal expansion difference between the core and clad not be so large as to shatter the resultant fiber upon cooling as addressed in greater detail below.
- the cladding tube After the cladding tube is filled, it can be drawn down into fiber or canes for overcladding.
- the filled tube is heated to soften the cladding glass for elongation.
- the core stick As the cladding tube softens during the draw, the core stick will melt, fine (removal of bubbles), and conform to the walls of the cladding tube forming an interface determined by the inner surface of the cladding tube.
- the ratio of the outer diameter (OD) to the inner diameter (ID) of the tube will be roughly the same as the fiber or cane OD/ID ratio although it can be controlled by the pressure (positive or negative) applied over the molten core relative to outside the cladding tube.
- the draw temperature can also be used to control the core diameter as higher draw temperatures will lead to smaller core diameters for the same given fiber OD. This control represents a substantial advantage over conventional preforms where this ratio is fixed once the blank is fabricated.
- the higher temperatures used to draw the cladding tube (2000°C for the case of pure Si0 2 cladding) serve to homogenize the core melt and drive off detrimental water in the glass.
- a vacuum can be applied to a centerline to enhance water removal and fining. Utilizing an open centerline during the first draw step allows for atmospheric control of the melt at the drawing temperature. Oxidizing as well as reducing atmospheres can be introduced above the melt to control the redox state of the core material or maintain reduced metallic cores or superconductors in a dielectric cladding.
- stress rods e.g. B 2 O 3 doped SiO 2 glass rods
- Such stress rods could be made via CVD and consolidated into glass, then placed within the bores drilled into the side walls of the tube.
- the stress rods could be comprised of a non-CVD formed glass (e.g. a melt glass) and placed within the bores of the side walls of the tube.
- the core glass feedstock could be fed into the inside diameter of the tube as described further herein.
- the resultant preform could be subsequently drawn to make a polarization maintaining fiber.
- two electrically conductive wires could be used in place of the stress rods (and likewise inserted into holes bored into the sidewalls of the tube) to make a fiber which may be used as an electro-optic switch (e.g., enabling application a voltage between the two wires to change the refractive index of the core).
- the pressure within the tube above the core can also be controlled to regulate the core diameter.
- This type of process control is not available with any of the current preform fiberization methods, and in the present invention, such control greatly facilitates the formation of certain combinations of tube and core glasses.
- vacuum assistance might not be important.
- vacuum application within the tube from above the core glass can be used to compensate for the forces of the melt glass pushing outwardly on the tube walls, thereby helping to maintain the internal shape of the tube walls.
- Controlled glass composition and thermal history can also be used to generate graded index profiles.
- the core is molten and the cladding is softening, diffusional processes are relatively fast, so graded index profiles can be created in situ.
- the fibers produced can be fusion spliced to conventional fibers making them quite practical in existing fiber networks and easing device manufacture.
- the first cladding tube could have a refractive index in between that of the core and the overclad tube to control the numerical aperture of the fiber or it could contain refractive index moats and rings inserted to engineer the dispersion and mode field diameter of the fiber.
- the first draw reduces the radial dimensions of the index profile by a factor of 6-8, and the second draw, reduces them down again by a factor of 400-500, so very fine structures can be achieved.
- FIG. 1 is a cross sectional drawing of an apparatus 100 which may suitably be used for implementing the filament in tube method of drawing optical fiber in accordance with the present invention.
- a cladding tube 112 having a 57 mm OD and a 2 mm ID in a preferred embodiment, with an inner wall 118 is purged with a drying gas, for example chlorine (Cl 2 ) or chlorine mixed with an inert gas, to remove unwanted moisture.
- a drying gas for example chlorine (Cl 2 ) or chlorine mixed with an inert gas, to remove unwanted moisture.
- This feedstock or filament 110 is preferably an elongated monolithic rod of material, however, a plurality of elongated rods can be stacked one atop the other within the cladding tube 112 to form the feedstock. Using a plurality of rods is particularly well suited for the production of dispersion managed fiber.
- the cladding tube 112 and the core filament 110 form a filled cladding tube with an open centerline 122 which is heated by a furnace 114, as described further below.
- the furnace 114 is operated at a draw temperature which is at or above the melting temperature of the core filament 110, but only causes the cladding tube 112 to soften.
- the core filament 110 will melt at the draw temperature forming a core melt 120 contained within the cladding tube 112. It is presently preferred that the draw temperature is at or above the liquidus temperature of the core filament to eliminate crystals in core melt 120.
- melt means that the core filament 110 flows and fills or deforms to the interior of the cladding tube 112 so that a filled cladding structure results.
- the core during the step in which the core melts and deforms to the interior of the tube, the core preferably exhibits a viscosity of less than 10 6 poise, more preferably 10 4 poise, most preferably 1000 poise or less, and the cladding structure maintains a viscosity sufficient for the cladding to substantially retain its internal shape.
- the cladding tube 112 exhibits a viscosity greater than 10 7'6 poise at this temperature. This distinguishes the present invention from the more conventional methods (e.g.
- the viscosity of the core and clad were typically matched so that both the rod and tube had a viscosity that differed by less than a factor of about 10 at the temperature at which the fiber is drawn or cane is drawn.
- An optical fiber 1 16 is then drawn. While melting, the core filament 110 will preferably fine and conform to the interior wall 118 of the cladding tube 112, forming an interface determined by the inner surface 118, and completely filling the interior of the cladding tube 112.
- a glass cladding material 112 has a viscosity of about 10 7 6 poise. For some types of SiO 2 , this occurs at a temperature of about 2000°C.
- the cladding material should be selected so that at the temperature at which the core material is filling the interior of the cladding tube it has a viscosity greater than 10 7 poise, and preferably greater than 10 7 6 , and most preferably greater than 10 8 .
- a core 120 such as 69.86 mole % silica (Si0 2 ), 18.63 mole % aluminum oxide (AI 2 O 3 ), 4.66 mole % sodium oxide (Na 2 O), and 6.85 mole % lanthanum fluoride (La 2 F 6 ) will have a viscosity of approximately 10 poise, seven orders of magnitude less than the cladding 112.
- the core 120 might suitably have a viscosity less than or equal to about 10 4 5 poise.
- a typical rod in tube process would typically employ both core and cladding material having substantially the same viscosity.
- the core filament 110 can be produced in any shape (round, square, triangular, etc.) and via any method (conventional crucible melting and casting, drawing, sol-gel, etc.). The only physical requirement is that the core filament 110 fit within the inner walls of the cladding tube 112. Thus, less rigid process controls are required during the manufacture of the core filament 110. Moreover, the loose fitting core filament 110 may be automatically fed down or dropped down as its bottom is melted to maintain a constant depth of molten core 120, yielding a homogeneous and reproducible optical fiber 116.
- the core filament 110 has a melting temperature, as defined above, which is below the softening temperature of the cladding 112, and the thermal expansion difference between the core filament 110 and the cladding 112 is not so large as to shatter the fiber 116 when it is cooled.
- the composition of the cladding 112 is preferably silicate glass, but it will be appreciated by those skilled in the art, that the composition of cladding 112 is essentially not limited and can range from pure SiO 2 to multicomponent glasses.
- FIG. 2 is a cross sectional drawing of an apparatus 200 which may suitably be employed for performing the stick in tube method of drawing optical fiber in accordance with the present invention.
- a one meter long Si0 2 cladding tube 212 (55 mm in outer diameter and 6 mm in inner diameter) is purged with drying gas to remove unwanted moisture.
- a 5 mm diameter core stick 210 is disposed or placed within the cladding tube 212 to form a filled cladding tube.
- the filled cladding tube is heated by a furnace 214 to 1700° C to soften the cladding tube 212 in preparation for elongation.
- the core stick 210 melts, and a 6 mm outer diameter optical core cane 216 is then drawn in a standard manner.
- cane or “core cane” as used herein, we mean an optical fiber precursor element comprising a core glass material, to which additional cladding must be added to the core cane prior to its being drawn into an optical fiber.
- additional cladding may be applied, for example, by inserting the cane into a glass cladding sleeve, or depositing additional core and/or cladding glass via outside vapor deposition or other methods. While melting, the core stick 210 will fine and conform to the interior walls of the cladding tube 212, forming an interface determined by the inner surface of the cladding tube 212.
- the cladding material 212 preferably has a viscosity of approximately 10 8 poise at the draw temperature (e.g. about 1700°C for some forms of silica) and the core stick 210 will have a viscosity of approximately 10 4 poise or less at the draw temperature.
- the resulting core cane 216 is then placed within an overcladding tube 220.
- the filled overcladding tube 220 is heated by a furnace 222 to soften the overcladding tube 220 in preparation for elongation.
- the overcladding tube 220 softens, the cane 216 will soften, and an optical fiber 224 is drawn.
- a core glass of molar composition 70.0 SiO 2 - 11.25 AI 2 O 3 - 7.5 Ta 2 O 5 - 10 CaO - 2 CaF 2 - .05 Er 2 0 3 was batched from high purity powders, mixed, calcined at 400°C for 12 hours to dry the batch, and then melted in a covered high purity silica crucible at 1650°C for 4 hours.
- the melt was stirred with a fused silica rod to promote homogeneity, then cooled to 1500°C and drawn up into a 4-5 mm diameter stick from the melt.
- the 5 mm diameter stick of core glass was then inserted into a meter long 55 mm outer diameter (OD), consolidated, Si0 2 blank previously manufactured using the outside vapor deposition process with a 6 mm inner diameter (ID).
- the tube was purged with dry He gas to remove unwanted moisture and heated to 1800°C to soften the SiO 2 blank and drawn down into a 6 mm diameter core/clad cane which was flame cut into 1 meter long pieces.
- a 1 meter long piece was then mounted on a CVD lathe and overclad with SiO 2 soot to obtain the desired clad diameter/core diameter ratio of 32:1.
- the overclad cane was then consolidated between 1440 and 1500°C to form a monolithic SiO 2 blank with a core. This blank was then heated to 1950-2000°C in a graphite resistance furnace and drawn into standard 125 micron diameter fiber at a rate of 2 m/s.
- the resultant fiber having an Er-doped core is suitable for use as an optical amplifier
- FIG. 3 is a drawing of an apparatus 300 used for overcladding an optical cane via an alternative CVD process and then drawing an optical fiber in accordance with the present invention.
- a cane 216 produced by the embodiment of the present invention shown in FIG. 2, is cut into 1 meter long pieces.
- the cut cane 216 is then mounted on a CVD lathe 332 and overclad with SiO 2 to obtain the desired ratio between the clad diameter and the core diameter, forming an overclad optical cane 330.
- the overclad cane 330 is then consolidated at a temperature between 1400° C and 1500° C to form a monolithic SiO 2 blank 336.
- FIG. 4 is a graph 400 showing loss as a function of wavelength for a 5 meter span of an optical fiber produced in accordance with the present invention.
- the low loss optical fiber (0.07 dB/m at 1310 nm) exhibits the same loss per meter, beginning to end, over a 2000 meter span.
- the core of the optical fiber was successfully doped with erbium ions, Er 3+ , as evidenced by the adsorption bands at 980 and 1500 nm. Additionally, Er 3+ fluorescence was observed from the optical fiber when 980 nm laser light was pumped into the fiber.
- Fig. 4 illustrates that, using the methods of the present invention, fiber can be made having a rare earth dopant therein which exhibit a background attenuation of less than 2 dB/m.
- FIG. 5 is a graph 500 showing the refractive index profile of a core cane produced in accordance with the present invention using the core glass composition described above with respect to Fig. 2.
- the core cane has a drawn diameter of 2.74 mm, the core of the cane having a diameter of .21 mm, for a core/clad thickness ratio of about .077.
- the core exhibited a refractive index delta of about .11 (with respect to the silica core), or a delta percent of about 6.76 percent (again with respect to the undoped silica cladding).
- the observed maximum delta of 6.76 percent is significantly higher than that seen for typical CVD produced fiber.
- the cane was subsequently overclad and drawn into 10,000 m of homogeneous optical fiber.
- the total core diameter variance over the 10,000 m span was ⁇ 0.25 ⁇ m, as compared to the cullet in tube method which would yield a variance of ⁇ 4 ⁇ m.
- fiber manufactured in accordance with the present invention shows an improvement of at least an order of magnitude.
- utilizing SiO 2 as the cladding material allowed the resultant optical fiber to be fusion spliced using conventional fusion splicers.
- FIG. 6 is a graph 600 showing loss as a function of wavelength for a 5 meter span of optical fiber produced in accordance with the present invention.
- a tube was made by depositing pure silica, followed by germania doped silica, followed by a pure silica cladding region. The resultant soot preform was consolidated to form a tube. Then, the same type of core glass rod described above with respect to Fig. 2 was inserted into the glass tube and drawn into a fiber.
- the resultant multi-component core in this case was comprised a central high index region surrounded by a silica moat, which was in turn surrounded by a ring of SiO 2 doped with germanium oxide (GeO 2 ).
- FIG. 7 is a graph 700 showing the loss and mode field diameter as a function of fiber length for an optical fiber produced in accordance with the present invention.
- Fig. 7 demonstrates that mode field diameters can be expanded by employing a raised index ring outside the central high index region of the core, to thereby expand the mode field diameter beyond that of a what would be achieved using a single raised index core. Minimal variations in loss and mode field diameter for varying lengths are achievable, as illustrated by Fig. 7.
- the method of the present invention has a variety of advantages.
- the method of the invention opens up a large range of compositions for fiberization that have not previously been attainable through conventional CVD techniques which have been employed to make optical fiber. New compositions with high rare earth solubility, improved gain flatness and improved optical properties can be readily fabricated into fiber form.
- the method also accommodates large differences in thermal expansion between the core filament 110 or core stick 210, and cladding material 112 or cladding material 212, since the core 110,
- the core filament 110 or core stick 210 is not rigidly bonded to the clad 112, 212 until the core filament 110 or core stick 210 is in fiber or cane form when the stress due to thermal expansion mismatch are much smaller than in a rigid monolithic preform of greater size, as these stress forces vary inversely with the square of the radius of the fiber, preform or the like. Accordingly, very large numerical aperture fibers for use as efficient couplers and lasers can be produced by the method of the present invention.
- the method also allows for atmospheric control of the core melt 120, 220 at the drawing temperature. Either oxidizing, reducing or chemically reactive atmospheres can be introduced utilizing the open centerline to control the redox state.
- the pressure above the core filament 110 or core stick 210 can be controlled to regulate the core diameter, as can the draw temperature.
- a core feedstock such as core feedstock 110
- the core feedstock could conceivably be hollow, or be divided into several large blocks.
- the term feedstock is intended to encompass a thin filament, a thicker stick, a plurality of elongated filaments bundled for insertion into the tube, or elongated filaments or sticks stacked axially one on top of the other for insertion into the tube, or the like, which will properly feed down upon melting.
- feedstock as defined herein preferably is not powder or cullet.
- the feedstock can be formed from a core material alone or from a core material having a cladding material disposed thereon. Either of these embodiments can then be disposed within a tube formed from cladding material.
- the tube can be formed from core material or cladding material.
- optical fiber should be construed as encompassing any fiber or fiber component employed in applications including but not limited to optical waveguides, single mode fibers, multi-mode fibers, amplifiers, electro-optical fibers, couplers, lasers, or the like. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention cover the modification and variations of this invention provided they come within the scope of the appended claims and their equivalents.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020017002806A KR20010082180A (en) | 1998-08-25 | 1999-08-24 | Methods and apparatus for producing optical fiber |
CA002341713A CA2341713A1 (en) | 1998-08-25 | 1999-08-24 | Methods and apparatus for producing optical fiber |
EP99964941A EP1108233A1 (en) | 1998-08-25 | 1999-08-24 | Methods and apparatus for producing optical fiber |
AU30966/00A AU3096600A (en) | 1998-08-25 | 1999-08-24 | Methods and apparatus for producing optical fiber |
JP2000580956A JP2002529357A (en) | 1998-08-25 | 1999-08-24 | Method and apparatus for manufacturing optical fiber |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US9787698P | 1998-08-25 | 1998-08-25 | |
US60/097,876 | 1998-08-25 |
Publications (1)
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WO2000027773A1 true WO2000027773A1 (en) | 2000-05-18 |
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Family Applications (2)
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PCT/US1999/016177 WO2000010932A1 (en) | 1998-08-25 | 1999-07-16 | Methods and apparatus for producing optical fiber |
PCT/US1999/019139 WO2000027773A1 (en) | 1998-08-25 | 1999-08-24 | Methods and apparatus for producing optical fiber |
Family Applications Before (1)
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PCT/US1999/016177 WO2000010932A1 (en) | 1998-08-25 | 1999-07-16 | Methods and apparatus for producing optical fiber |
Country Status (10)
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EP (1) | EP1108233A1 (en) |
JP (1) | JP2002529357A (en) |
KR (1) | KR20010082180A (en) |
CN (1) | CN1324334A (en) |
AU (2) | AU5316699A (en) |
CA (1) | CA2341713A1 (en) |
ID (1) | ID29631A (en) |
TW (1) | TW440718B (en) |
WO (2) | WO2000010932A1 (en) |
ZA (1) | ZA200101616B (en) |
Cited By (7)
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EP1199286A1 (en) * | 2000-10-18 | 2002-04-24 | The University Of Southampton | Optical fibres and preforms incorporating volatile constituents and process for manufacturing the fibre |
EP1207140A1 (en) * | 2000-11-20 | 2002-05-22 | Lucent Technologies Inc. | Method for making electrically controllable optical fiber devices |
WO2005019889A1 (en) * | 2003-08-21 | 2005-03-03 | Federalnoe Gosudarstvennoe Unitarnoe Predpyatie 'vserossiysky Nauchny Tsentr 'gosudarstvenny Optichesky Institut Im. S.I.Vavilova' (Fgup Goi) | Single-mode electrooptical fibre and method for the production thereof |
WO2007009450A1 (en) * | 2005-07-20 | 2007-01-25 | J-Fiber Gmbh | Method for producing glass-fibre preforms with a large core diameter |
CN101503275B (en) * | 2009-03-11 | 2011-03-16 | 哈尔滨工程大学 | Electrostatic loading optical fiber embedding apparatus for optical fiber prefabricated bar |
WO2013170254A1 (en) * | 2012-05-11 | 2013-11-14 | Ofs Fitel, Llc | Barbell optical fiber and method of making the same |
US8639078B2 (en) | 2011-12-19 | 2014-01-28 | Olympus Corporation | Optical fiber manufacturing method, optical fiber and endoscope |
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1999
- 1999-07-16 AU AU53166/99A patent/AU5316699A/en not_active Abandoned
- 1999-07-16 WO PCT/US1999/016177 patent/WO2000010932A1/en active Application Filing
- 1999-08-24 ID IDW20010689A patent/ID29631A/en unknown
- 1999-08-24 KR KR1020017002806A patent/KR20010082180A/en not_active Application Discontinuation
- 1999-08-24 JP JP2000580956A patent/JP2002529357A/en not_active Withdrawn
- 1999-08-24 CN CN99812479A patent/CN1324334A/en active Pending
- 1999-08-24 EP EP99964941A patent/EP1108233A1/en not_active Withdrawn
- 1999-08-24 AU AU30966/00A patent/AU3096600A/en not_active Abandoned
- 1999-08-24 TW TW088114670A patent/TW440718B/en not_active IP Right Cessation
- 1999-08-24 WO PCT/US1999/019139 patent/WO2000027773A1/en not_active Application Discontinuation
- 1999-08-24 CA CA002341713A patent/CA2341713A1/en not_active Abandoned
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2001
- 2001-02-27 ZA ZA200101616A patent/ZA200101616B/en unknown
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US5110334A (en) * | 1990-07-31 | 1992-05-05 | The United States Of America As Represented By The Secretary Of The Navy | Method of producing glass fiber with cores of a different material |
US5689578A (en) * | 1993-02-25 | 1997-11-18 | Fujikura Ltd. | Polarized wave holding optical fiber, production method therefor, connection method therefor, optical amplifier, laser oscillator and polarized wave holding optical fiber coupler |
US5533163A (en) * | 1994-07-29 | 1996-07-02 | Polaroid Corporation | Optical fiber structure for efficient use of pump power |
EP0842907A1 (en) * | 1996-11-19 | 1998-05-20 | CSELT Centro Studi e Laboratori Telecomunicazioni S.p.A. | Active single mode optical fibres and method for their fabrication |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1199286A1 (en) * | 2000-10-18 | 2002-04-24 | The University Of Southampton | Optical fibres and preforms incorporating volatile constituents and process for manufacturing the fibre |
EP1207140A1 (en) * | 2000-11-20 | 2002-05-22 | Lucent Technologies Inc. | Method for making electrically controllable optical fiber devices |
WO2005019889A1 (en) * | 2003-08-21 | 2005-03-03 | Federalnoe Gosudarstvennoe Unitarnoe Predpyatie 'vserossiysky Nauchny Tsentr 'gosudarstvenny Optichesky Institut Im. S.I.Vavilova' (Fgup Goi) | Single-mode electrooptical fibre and method for the production thereof |
WO2007009450A1 (en) * | 2005-07-20 | 2007-01-25 | J-Fiber Gmbh | Method for producing glass-fibre preforms with a large core diameter |
CN101503275B (en) * | 2009-03-11 | 2011-03-16 | 哈尔滨工程大学 | Electrostatic loading optical fiber embedding apparatus for optical fiber prefabricated bar |
US8639078B2 (en) | 2011-12-19 | 2014-01-28 | Olympus Corporation | Optical fiber manufacturing method, optical fiber and endoscope |
EP2689710A4 (en) * | 2011-12-19 | 2015-04-29 | Olympus Corp | Method for producing optical fiber, optical fiber, and endoscope |
WO2013170254A1 (en) * | 2012-05-11 | 2013-11-14 | Ofs Fitel, Llc | Barbell optical fiber and method of making the same |
Also Published As
Publication number | Publication date |
---|---|
ID29631A (en) | 2001-09-06 |
ZA200101616B (en) | 2001-09-17 |
EP1108233A1 (en) | 2001-06-20 |
JP2002529357A (en) | 2002-09-10 |
WO2000010932A1 (en) | 2000-03-02 |
TW440718B (en) | 2001-06-16 |
KR20010082180A (en) | 2001-08-29 |
CN1324334A (en) | 2001-11-28 |
AU3096600A (en) | 2000-05-29 |
CA2341713A1 (en) | 2000-05-18 |
AU5316699A (en) | 2000-03-14 |
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