WO2000003217A2 - Forme composite utile en tant que composant pour un capteur de pression - Google Patents

Forme composite utile en tant que composant pour un capteur de pression Download PDF

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Publication number
WO2000003217A2
WO2000003217A2 PCT/US1999/012721 US9912721W WO0003217A2 WO 2000003217 A2 WO2000003217 A2 WO 2000003217A2 US 9912721 W US9912721 W US 9912721W WO 0003217 A2 WO0003217 A2 WO 0003217A2
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WO
WIPO (PCT)
Prior art keywords
elongated body
change
pressure transducer
optical fiber
pressure
Prior art date
Application number
PCT/US1999/012721
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English (en)
Other versions
WO2000003217A3 (fr
Inventor
Peter C. Ogle
Arthur D. Hay
Alan D. Kersey
Original Assignee
Cidra Corporation
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Filing date
Publication date
Application filed by Cidra Corporation filed Critical Cidra Corporation
Priority to AU13072/00A priority Critical patent/AU1307200A/en
Publication of WO2000003217A2 publication Critical patent/WO2000003217A2/fr
Publication of WO2000003217A3 publication Critical patent/WO2000003217A3/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
    • G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
    • G01L1/246—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre using integrated gratings, e.g. Bragg gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
    • G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
    • G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/3537—Optical fibre sensor using a particular arrangement of the optical fibre itself
    • G01D5/35377—Means for amplifying or modifying the measured quantity

Definitions

  • the present invention pertains to the measurement of pressure, including both hydrostatic pressure and acoustic pressure, and in particular to a composite structure as a component of a pressure transducer for changing shape in response to pressure.
  • a pressure transducer typically consists of two general components: a component that responds mechanically to a change in pressure, i.e. by e.g. changing shape, and a component that senses the mechanical response of the other component and provides a signal that can be correlated with the mechanical response, i.e. a strain sensor.
  • the mechanically responding component is often a cylindrical body.
  • One way of measuring pressure is to sense how a cylindrical body will lengthen, in what is called Poisson's effect, in response to pressure imposing a radial stress on the body leading to circumferential stress, also called hoop stress.
  • Poisson's effect when pressure, such as fluid pressure, squeezes radially on a cylindrical body, the body tends to lengthen as it thins, i.e. it experiences axial strain as well as circumferential strain.
  • the prior art also teaches that it is also useful to sense how a cylindrical body thins, instead of how it lengthens, in response to an increase in pressure acting on the cylindrical walls of the cylindrical body. Sensing either aspect of the mechanical response, either the lengthening or thinning response to an increase in pressure, can be done by the second component of a pressure transducer.
  • a fiber optic having a Bragg grating
  • a Bragg grating is created over a length of a fiber optic by exposing segments along the length to different light in the ultraviolet range causing different indices of refraction.
  • the axial strain is then detected by interferometry, i.e.
  • the Bragg grating when light is passed through the fiber, the Bragg grating causes an interference pattern that depends on the length over which the Bragg grating extends; when the length changes, as a result for example of fluid pressure and Poisson's effect, the pattern changes and does so in a way that allows the change in length to be determined, which can then be correlated with pressure that caused the change in length.
  • An alternate method of using an optical fiber Bragg grating as one component of a pressure transducer to sense how a cylindrical body, serving as the other component, strains axially in response to a change in pressure is to create a Bragg grating on either end of a length of optical fiber lengthening as a result of Poisson's effect.
  • This method has a far greater sensitivity than the single Bragg grating approach, because a greater length of fiber is strained yielding a greater overall change in length.
  • the ratio of the orthogonal strain to the parallel strain is known as Poisson's ratio and is an indicator of the magnitude of Poisson's effect for the particular material or structure composing the body.
  • bare optical fiber i.e. unsheathed optical fiber is often used, so that the optical fiber having a Bragg grating is exposed to the full pressure, undiminished by any sheathing.
  • bare optical fibers are susceptible to abrasion and chemical attack, so that in some applications, using ensheathed optical fibers is not practical.
  • bare optical fibers are sheathed in a fine diameter steel capillary tube filled with fluid to protect against chemical attack and abrasion.
  • a sheathing reduces the sensitivity of the optical fiber.
  • steel tubing has a different coefficient of thermal expansion than optical fiber material, and this difference creates thermal-based axial strains that compound the pressure measurement. If one could assume that the optical fiber would expand with the steel capillary, one could subtract out the effect of the thermal strains.
  • the optical fiber can slip within the metal capillary, so the thermally induced strains are difficult to predict and thus distinguish from pressure induced strain.
  • an optical fiber is made more sensitive to pressure by encapsulating or jacketing the optical fiber in a soft polymer having a relatively low bulk modulus of elasticity and a relatively high Young's modulus, and using a jacket outer diameter as large as
  • the bare optical fiber itself will respond to temperature changes by undergoing thermal expansion or contraction in both length and diameter, but these changes in dimension can be compensated for by using a second grating that is not exposed to the pressure.
  • a second grating that is not exposed to the pressure.
  • even a flowing of fluid over the optical fiber can, through shear stresses, impart axial stresses that interfere in the pressure measurement.
  • a mechanical form for use as the mechanical component of a pressure transducer, that will not itself experience significant thermal strains, but will exhibit a pronounced Poisson's effect when exposed to a change in pressure acting on the mechanical form, and so exhibit significant axial and longitudinal strains.
  • the mechanical form should not reduce the sensitivity of the optical fiber to the pressure being measured, even if it ensheathes the optical fiber and so protects the optical fiber against abrasion and chemical attack.
  • a cylindrical body used as the mechanical component of a pressure sensor can extend over a distance spanning regions where sensitivity to pressure is not wanted, and other regions where it is. Because of this, an even more advantageous mechanical form would allow varying sensitivity to pressure along its length, so that it is more sensitive to pressure along some spans, and substantially insensitive along other spans.
  • Another important advantage would be for the mechanical form to be producible in a continuous batch process, so that there would be no break between lengths of the form intended to exhibit different sensitivities to pressure.
  • the manufacturing process would produce, as the mechanical form, a continuous material, although differing in its construction in different spans, according to the level of response to pressure wanted by the different spans.
  • the present invention provides, as the mechanical component of a pressure transducer, a mechanical form that is an elongated body including a layer of contra-helically- wound reinforcing fibers, which may be bi-axially braided, arranged along the elongated body, the mechanical form for providing a change in shape in response to a change in pressure.
  • a mechanical form is also referred to as a composite form, because it is made from both resin material as well as reinforcing fibers, which are a different material from the resin.
  • a pressure transducer based on a mechanical form according to the present invention would also include a means of sensing the change in shape of the mechanical form and providing a signal based on the change in shape, i.e. a strain sensor.
  • the means of sensing the change in shape is based on an optical fiber affixed to the elongated body so as to change in length in proportion to the change in shape of at least a portion of the elongated body, where the optical fiber has a Bragg grating as part of the optical fiber.
  • Such an optical fiber is disposed either lengthwise along the elongated body, or is spirally wrapped over at least one layer of the elongated body.
  • the reinforcing fibers are embedded in a resin system, usually based on an elastomeric material having a low to moderate Young's modulus.
  • there is a second layer of contra-helically-wound reinforcing fibers which may be bi-axially braided.
  • the two layers of reinforcing fibers are arranged so as to have a similar scissor action in response to pressure; along spans where the elongated body is intended to be insensitive, the two layers are arranged to have different scissor actions, a situation in which a change in length of the elongated body is inhibited.
  • the mechanical form uses an elastomeric material, for its resin, having a coefficient of thermal expansion substantially similar to the coefficient of thermal expansion for the optical fiber.
  • Fig. 1 is a schematic cross-sectional view of a mechanical form, according to the present invention, for use as a component of a pressure transducer, in an embodiment having two layers of contra-helically wound, bi-axially braided reinforcing fibers;
  • Fig. 2 is a cut-away view of a span of the mechanical form of Fig. 1, showing an inner and outer layer of contra-helically wound, but not braided, reinforcing fibers with the same polar angle for each;
  • Fig. 3 is a cut-away view of a span of the mechanical form of Fig. 1, showing an inner and outer layer of contra-helically wound, not braided, reinforcing fibers with different polar angles;
  • Fig. 4 is a diagrammatic representation of scissoring, under the influence of pressure and resulting circumferential strain, by spans of two reinforcing fibers, one from each of two contra-helically wound reinforcing fibers of one layer;
  • Fig. 5a is a cross-sectional view of a fiber-optic pressure transducer, with multiple optical fibers ensheathed by the mechanical form of the present invention
  • Fig. 5b is a perspective view of the fiber-optic pressure transducer of Fig. 5a;
  • Fig. 6a is a cross-sectional view of a fiber-optic pressure transducer with an optical fiber wrapped around the mechanical form of the present invention
  • Fig. 6b is a perspective view of the fiber-optic pressure transducer of Fig. 6a.
  • a mechanical form 10 for use as a component of a pressure transducer, is shown having an outer annular layer of contra-helically wound and braided reinforcing fibers 12 on top of another, inner annular layer of contra-helically wound and braided reinforcing fibers 13, with both layers encapsulated by a resin 17 filling interstitial spaces between a core region 20 and a form covering 11, and also wetting the fibers 12 and 13 of the two layers.
  • the two layers are distinguished by the dashed line 18.
  • the resin 17 is a polymer having a low to moderate Young's modulus of elasticity, i.e. from approximately 0.5-50.0 ksi.
  • the mechanical form 10 deforms more or less in response to pressure acting on it, as explained below; along some spans of the mechanical form, the reinforcing fibers are arranged so that the mechanical form is substantially insensitive to changes in pressure acting on it, and along other spans, the reinforcing fibers are arranged so that the mechanical form is especially sensitive to changes in pressure, i.e. it is made to deform in a particular way, for example by lengthening, more than an isotropic material would deform in that particular way, as explained below.
  • a pressure transducer based on the mechanical form 10 includes in the core region 20, as the component that senses the change in shape of the mechanical form 10, i.e. the strain sensor component, at least one optical fiber 15 having a fiber buffer coating 14 and having at least one Bragg grating.
  • the mechanical form in a span of the mechanical form that is made sensitive to pressure, as the pressure increases, the mechanical form will, preferably, lengthen, and the optical fibers within the core region 20 will stretch correspondingly, since they are coupled to the mechanical form as explained below.
  • the component for sensing the change in shape of the mechanical form 10, of which an optical fiber having a Bragg grating is just an example is not necessarily located in the core region 20.
  • the core region 20 is advantageously filled with a silicon gel, or some other compliant material.
  • a thin-walled, compliant, air-backed cylinder may be located in the core region.
  • a mechanical form 10 is shown in the region where it is intended to be sensitive to fluid pressure.
  • the mechanical form 10 again includes two layers of contra-helically wound reinforcing fibers 12 and 13, but the reinforcing fibers 12 and 13 are not braided.
  • the cutaway view shows the inner layer and outer layer.
  • the reinforcing fibers 12 of the outer layer are arranged to have two different axes, i.e. to lie along two different directions.
  • the reinforcing fibers in one direction make an angle 2 ⁇ relative to the reinforcing fibers in the other direction, or an angle ⁇ with respect to the bisector 19 of the total angle 2 ⁇ between any two non-parallel reinforcing fibers.
  • the angle ⁇ of a layer is here called the polar angle of that layer.
  • the mechanical form is constructed out of layers of reinforcing fibers with polar angles ranging from approximately 5° to 85°.
  • the rate of elongation depends on the polar angle
  • the two layers when the two layers are wound with significantly different polar angles, preferably polar angles that differ by as much as 30°, the two layers will tend to elongate at significantly different rates, but because the two layers are coupled through the resin 17 (see Fig. 1), elongation of the two layers at different rates is made difficult, so the mechanical form tends not to elongate at all.
  • the mechanical form is essentially an isotropic material and can have at best, for purposes of sensing pressure, a Poisson's ratio of approximately 0.20.
  • An optimum polymer material for a mechanical form will at best have a Poisson's ratio of 0.50; thus the actual strain can only be one-half the radial or circumferential strain.
  • the contra-helically wound mechanical form of the present invention is non-isotropic and it is possible for it to have a Poisson's ratio of greater than one-half, and in fact as much as one or two.
  • a span of a mechanical form 10 intended to be insensitive to fluid pressure has an outer layer of contra-helically wound reinforcing fibers 12 and an inner layer of contra-helically wound reinforcing fibers 13, where the two layers have different polar angles.
  • the polar angles of the two layers both differ from the single polar angle in a sensitive span, but by opposite amounts.
  • the basis for the control of Poisson's ratio for the mechanical form is that the polar angle controls the rate of axial strain per unit circumferential strain, because the reinforcing fibers in the contra-helical winding stretch very little themselves, and the elongation of the mechanical form results purely from scissoring of the contra-helical windings.
  • Fig. 4 shows two reinforcing fibers 16 of a contra-helical winding closing under the influence of a radial stress F.
  • the polar angle q decreases, and it is easy to show that the rate of change of the length / of the reinforcing fiber with change in q is given by
  • Using a polymer for the resin 17 can create problems stemming from thermal expansion.
  • Most polymers used for a resin system have an inherently high and undesirable coefficient of thermal expansion (CTE).
  • Thermal expansion of the resin can be controlled somewhat by using polar angles in some particular ranges. A polar angle of 20° will provide, even for the overall structure of a pressure transducer using optical fibers, near-zero thermal expansion in the axial (lengthwise) direction of the mechanical form, while a polar angle of 30° will provide, overall for the same kind of pressure transducer, a large negative
  • a pressure transducer 22 based on a mechanical form 10 has a bundle of optical fibers 15 each having a fiber coating 14, all ensheathed by a low to moderate Young's modulus resin 17 reinforced by two layers of contra-helically wound reinforcing fibers 12 and 13 (see Figs 2 and 3) all surrounded by a form covering 11.
  • the outer-lying of the reinforcing fibers 12 are placed in intimate contact with the inner lying reinforcing fibers 13 through their coatings 14 of the optical fibers 15.
  • the reinforcing (non-optical) fibers 12 and 13 can be, for example, E- glass fibers.
  • the reinforcing fibers occupy approximately 50% of the volume between the buffer coatings 14 and the form covering 11 ; the rest is filled with resin 17.
  • Such a pressure transducer is useful for measuring pressure at different places using a single mechanical form, responding to pressure differently along different spans by virtue of how its reinforcing fibers 12 and 13 are arranged, as described above.
  • the ensheathed optical fibers would each have one or more Bragg gratings arranged to provide information about the response of the mechanical form 10 at different spans along the mechanical form.
  • each might have a pair of Bragg gratings bracketing a span of the mechanical form located in a region where the pressure is to be measured, or might have a single Bragg grating extending over such a span.
  • a single optical fiber has a series of Bragg gratings to convey information, by reflecting and altering a portion of an optical signal, about the pressure response of the mechanical form at various spans along the mechanical form.
  • a pressure transducer 23 based on a mechamcal form 10 has an optical fiber 15, having a fiber coating 14, overwrapping the mechanical form 10, where the mechanical form 10 is again constructed from a low to moderate Young's modulus resin 17 reinforced by two layers of contra-helically wound reinforcing fibers 12 and 13 (see Figs 2 and 3), and has a form covering 11, but does not ensheathe optical fibers and instead has a core region 20; the core region should be any material or construction that will not inhibit the desired response of the mechanical form 10.
  • the core region might be even simply a void (air-filled), or may be a silicone gel, which would comply with any tendency of the mechanical form to elongate.
  • the core region can be simply a void or filled with a silicone gel, but if the pressure to be resisted is high, the core region is advantageously filled with a material that tends not to strain circumferentially.
  • the reinforcing fibers occupy approximately 50% of the volume between the core region and the form covering 11; the rest is filled with resin 17.
  • the optical fiber in this application preferably includes a series of Bragg gratings to provide, in a multiplexed signal, information about the pressure response of the mechanical form 10 at a series of span locations along the mechanical form.
  • a pressure transducer based on a mechanical form In constructing a pressure transducer based on a mechanical form according to the present invention, and using ensheathed optical fibers each having a Bragg grating as a means for sensing a change in shape of the mechanical form (see again Fig. 5 a and 5b), first the coating 14 is checked to ensure it is approximately 400 microns deep, and if it is less, some additional coating material, usually silicone, is added to build up the coating 14 on each optical fiber 15, until the total thickness of the coating amounts to approximately 400 microns. Then the first and second layers of reinforcing fibers are arranged over the buffer coatings 14, and in the preferred embodiment, these layers are both bi-axially braided, with the outer layer immediately on top of the inner layer.
  • some additional coating material usually silicone
  • the assembly is shrink-wrapped in a skin of some suitable material, and the resin 17 is caused to impregnate, under vacuum and pressure, the space between the buffer coatings 14 and the form covering 11.
  • the resin moves between the reinforcing fibers because of the applied pressure, and penetrates or wets the reinforcing fibers as a combined result of the applied pressure and capillary forces.
  • the shrink-wrap is removed.
  • the resin can also be caused to impregnate the space between the buffer coatings 14 and the form covering 11 by other means, such, for example, pultrusion.
  • the form covering 11 is advantageously a high temperature polymer, such as the high temperature polymers disclosed in co-pending U.S.
  • PTFE polytetrafluoroethylene
  • an additional buffer coating (not shown) is advantageously provided.
  • Such a buffer coating is based on the same high temperature polymers as the form covering 11. In such an application, the form covering 11 can be eliminated.
  • any wavelength tunable grating or reflective element embedded in an optical fiber may be used if desired.
  • a data acquisition unit has a broadband light source or laser diode with suitable photo optic couplers.
  • Demodulators and filtering equipment can be used to monitor the shift in the wavelength of light reflected by a Bragg grating caused by strain undergone by the Bragg grating.
  • a Bragg grating When a Bragg grating is illuminated, it reflects a narrow band of light at a specified wavelength.
  • a measurand such as strain induced by pressure or temperature, will cause a change in the Bragg grating spacing, shifting the wavelength of the light it reflects.
  • the value of the measurand is directly related to the shift in the wavelength of the light reflected by the Bragg grating. If more than one Bragg grating is used, wave division multiplexing techniques can be used to sense the shifts in wavelength of the light reflected from each individual Bragg grating.
  • a readout device can be positioned so that a continuous reading of strain can be provided.
  • Patent Nos. 4,996,419; 5,361,130; 5,401,956; 5,426,297; and/or 5,493,390 all of which are hereby incorporated by reference.
  • These approaches may be generally categorized as follows: a) direct spectroscopy utilizing conventional dispersive elements, such as line gratings or prisms, and a linear array of photodetector elements; b) passive optical filtering with a device having a wavelength-dependent transfer function; c) tracking using a tuneable filter such as, for example, a scanning Fabry-Perot filter, an acousto-optic filter such as the filter described in the above referenced U.S. Patent No.
  • an optical fiber between a pair of gratings may be doped with a rare earth dopant (such as erbium) to create a tunable fiber laser, such as is described in US Patent No. 5,317,576, "Continuously Tunable Single Mode Rare-Earth Doped Laser Arrangement", to Ball et al or US Patent No. 5,513,913, “Active Multipoint Fiber Laser Sensor", to Ball et al, or US Patent No. 5,564,832, "Birefringent Active Fiber Laser Sensor", to Ball et al, which are incorporated herein by reference.
  • a rare earth dopant such as erbium
  • the various strain sensors may be multiplexed along the single optical fiber using wavelength division multiplexing (WDM), time division multiplexing (TDM), or other multiplexing techniques.
  • WDM wavelength division multiplexing
  • TDM time division multiplexing
  • the strain sensors may be configured using any type of optical grating-based measurement technique, e.g., scanning interferometric, scanning Fabry-Perot, acousto-optic tuned filter, optical filter, time of flight, etc. having sufficient sensitivity to measure the changes in the circumference of the pipe, such as that described in one or more of the following references: A. Kersey et al., "Multiplexed fiber Bragg grating strain-sensor system with a Fabry-Perot wavelength filter", Opt. Letters, Vol 18, No. 16, Aug. 1993, US Patent No. 5,493,390, issued Feb. 20, 1996 to Mauro Verasi, et al., US Patent No. 5,317,576, issued
  • known interferometric techniques may be used to determine the length or change in length of the optical fiber around the mechanical form due to pressure, such as Mach Zehnder or Michaelson Interferometric techniques, as described in US
  • Patent 5,218,197 entitled “Method and Apparatus for the Non-Invasive Measurement of Pressure Inside Pipes Using a Fiber Optic Interferometer Sensor” to Carroll.
  • Interferometric sensors may be multiplexed as described in Dandridge, et al, "Fiber Optic Sensors for Navy Applications", LEEE, Feb. 1991, or Dandridge, et al, “Multiplexed Interferometric Fiber Sensor Arrays", SPLE, Vol. 1586, 1991 , pp 176- 183. Other techniques to determine the change in fiber length may be used.
  • optical fiber it is also possible to wrap an optical fiber around only a portion of the mechanical form in order to sense a change in circumference of the mechanical form because of a change in pressure, provided the length of optical fiber is long enough to optically detect changes to the circumference.
  • the grating would be attached to the mechanical form, and the reflection wavelength of the grating would shift with changes in circumference of the mechanical form.
  • known Fabry-Perot, interferometric, time of flight or fiber laser sensing techniques may be used to measure the fiber length or change in fiber length due to a change in circumference, in a manner such as that described in the aforementioned references.
  • a pressure transducer can use any kind of strain sensor in combination with the here disclosed mechanical form.
  • a piezoelectric strain sensor could be used to sense the change in shape of the mechanical form.
  • Such a strain sensor could then be arranged to provide either an electrical or optical signal, and such signals could be multiplexed in various ways known in the art, to allow for a series of pressure transducers arranged over a single optical fiber.
  • the present invention could be used in any application, including a harsh environment such as an oil or gas well.

Abstract

Un capteur de pression utilise en tant que composant dont la forme doit changer en réponse à un changement de la pression qu'on mesure, un corps allongé composite doté de fibres de renforcement disposées de manière spécifique. Un tel capteur de pression peut utiliser divers dispositifs pour mesurer le changement de la forme du corps allongé, y compris une fibre optique fixée sur le corps allongé de manière à changer lui-même de longueur en réponse à un changement de la pression, et comprenant un réseau de Bragg faisant partie de la fibre optique, ce réseau de Bragg étant placé et configuré pour transporter, suite à un signal optique, de l'information concernant le changement de la forme du corps allongé. Le corps allongé est pourvu d'au moins une paire de fibres de renforcement enroulées dans le sens hélicoïdal inverse, qui peuvent même être tressées de manière biaxiale, et qui sont enroulées soit pour amplifier l'effet de la pression s'exerçant sur le corps allongé, soit pour isoler le corps allongé des effets de la pression et d'autres sources de contrainte. Les fibres de renforcement sont noyées dans une résine, et dans certaines applications plus d'une paire de fibres de renforcement enroulées dans le sens hélicoïdal inverse sont utilisées, de sorte que le corps composite est constitué de plus d'une couche de fibres de renforcement. Le corps allongé résultant est un matériau non isotrope et peut être formé pour que sont coefficient de Poisson soit sensiblement supérieur à 1/2, qui est le coefficient de Poisson maximum possible pour un matériau anisotrope, ceci produisant une contrainte axiale améliorée associée à une contrainte radiale ou circonférentielle. Le corps allongé peut également être formé pour avoir un faible coefficient de Poisson et ce au moyen de l'utilisation d'une couche interne et d'une couche externe d'enroulements hélicoïdaux inverses dans lesquels les fibres de renforcement des deux couches se recoupent à des angles différents.
PCT/US1999/012721 1998-06-05 1999-06-07 Forme composite utile en tant que composant pour un capteur de pression WO2000003217A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU13072/00A AU1307200A (en) 1998-06-05 1999-06-07 Composite form as a component for a pressure transducer

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US9055598A 1998-06-05 1998-06-05
US09/090,555 1998-06-05
US32409899A 1999-06-04 1999-06-04
US09/324,098 1999-06-04

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WO2000003217A2 true WO2000003217A2 (fr) 2000-01-20
WO2000003217A3 WO2000003217A3 (fr) 2000-05-18

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE1014702A3 (nl) * 2002-03-13 2004-03-02 Voet Marc Optische kabel voor het meten van temperatuur en/of rek en werkwijze voor het vervaardigen ervan.
US11796353B2 (en) 2017-01-31 2023-10-24 Optasense Holdings Limited Cable for distributed sensing

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4725110A (en) * 1984-08-13 1988-02-16 United Technologies Corporation Method for impressing gratings within fiber optics
EP0379650A1 (fr) * 1989-01-23 1990-08-01 SICOM Gesellschaft für Sensor- und Vorspanntechnik mbH Capteur à fibre optique pour forces de traction et de compression petites
DE19726731C1 (de) * 1997-06-24 1998-04-23 Daimler Benz Aerospace Ag Sensorkabel

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4725110A (en) * 1984-08-13 1988-02-16 United Technologies Corporation Method for impressing gratings within fiber optics
EP0379650A1 (fr) * 1989-01-23 1990-08-01 SICOM Gesellschaft für Sensor- und Vorspanntechnik mbH Capteur à fibre optique pour forces de traction et de compression petites
DE19726731C1 (de) * 1997-06-24 1998-04-23 Daimler Benz Aerospace Ag Sensorkabel

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE1014702A3 (nl) * 2002-03-13 2004-03-02 Voet Marc Optische kabel voor het meten van temperatuur en/of rek en werkwijze voor het vervaardigen ervan.
US11796353B2 (en) 2017-01-31 2023-10-24 Optasense Holdings Limited Cable for distributed sensing

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