WO2022199637A1 - 光纤温度传感器及传感头结构 - Google Patents

光纤温度传感器及传感头结构 Download PDF

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Publication number
WO2022199637A1
WO2022199637A1 PCT/CN2022/082610 CN2022082610W WO2022199637A1 WO 2022199637 A1 WO2022199637 A1 WO 2022199637A1 CN 2022082610 W CN2022082610 W CN 2022082610W WO 2022199637 A1 WO2022199637 A1 WO 2022199637A1
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Prior art keywords
interferometer
fiber
spectral range
pdms
free spectral
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PCT/CN2022/082610
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English (en)
French (fr)
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刘洺辛
杨玉强
王骥
牟小光
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广东海洋大学
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Priority to US17/910,520 priority Critical patent/US11761827B2/en
Publication of WO2022199637A1 publication Critical patent/WO2022199637A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • 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
    • G01D5/35312—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 Fabry Perot
    • 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
    • G01D5/35322—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 interferometer with one loop with several directions of circulation of the light, e.g. Sagnac interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K5/00—Measuring temperature based on the expansion or contraction of a material
    • G01K5/48—Measuring temperature based on the expansion or contraction of a material the material being a solid
    • G01K5/56—Measuring temperature based on the expansion or contraction of a material the material being a solid constrained so that expansion or contraction causes a deformation of the solid
    • G01K5/58—Measuring temperature based on the expansion or contraction of a material the material being a solid constrained so that expansion or contraction causes a deformation of the solid the solid body being constrained at more than one point, e.g. rod, plate, diaphragm
    • 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
    • G02B6/024—Optical fibres with cladding with or without a coating with polarisation maintaining properties
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
    • G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29331—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by evanescent wave coupling
    • G02B6/29335—Evanescent coupling to a resonator cavity, i.e. between a waveguide mode and a resonant mode of the cavity
    • G02B6/29338—Loop resonators
    • G02B6/2934—Fibre ring resonators, e.g. fibre coils
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/29347—Loop interferometers, e.g. Sagnac, loop mirror
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/29358—Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator
    • G02B6/29359—Cavity formed by light guide ends, e.g. fibre Fabry Pérot [FFP]
    • 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
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B2006/12133—Functions
    • G02B2006/12157—Isolator

Definitions

  • Embodiments of the present invention relate to the field of optical fiber sensing, and more particularly, embodiments of the present invention relate to an optical fiber temperature sensor, a sensor head structure, and a manufacturing method.
  • Optical fiber temperature sensors have many advantages such as small size, high measurement accuracy, high sensitivity, strong anti-electromagnetic interference, good electrical insulation, and large temperature range, and have their own unique advantages in temperature measurement.
  • embodiments of the present invention are expected to provide an optical fiber temperature sensor, a sensor head structure, and a manufacturing method, so as to further improve the temperature measurement sensitivity of the optical fiber temperature sensor.
  • an optical fiber temperature sensor in a first aspect of the embodiments of the present invention, includes a broad-spectrum light source, a first optical fiber coupler, a spectrometer, a first sensing interferometer, and a second sensing interferometer ; wherein, the first sensing interferometer and the second sensing interferometer have opposite temperature responses; the first free spectral range corresponding to the first sensing interferometer and the second sensing interferometer The corresponding second free spectral ranges are close but not equal.
  • the optical fiber temperature sensor comprises a Sagnac interferometer composed of a second optical fiber coupler and a polarized optical fiber;
  • the second sensing interferometer Interferometers include F-P interferometers connected by a single-mode fiber and a polydimethylsiloxane (PDMS) cavity.
  • PDMS polydimethylsiloxane
  • the incident light output by the broadband light source is divided into two paths after passing through the fiber isolator and the first fiber coupler in sequence, and one path enters the Sagnac interferometer.
  • another path enters the F-P interferometer through the attenuator, and obtains the superposition result of the interference spectrum returned by the Sagnac interferometer and the interference spectrum returned by the F-P interferometer through the spectrometer;
  • the second optical fiber The first end of the coupler is connected to the first fiber coupler, the polarization fiber is connected between the second end and the third end of the second fiber coupler, and the incident light entering the Sagnac interferometer is at The polarizing fiber is divided into two beams whose polarization directions are perpendicular to each other.
  • the length of the polarizing fiber and the axial length of the PDMS cavity are set such that the first free spectral range of the Sagnac interferometer is close to but not equal to the second free spectral range of the F-P interferometer.
  • temperature sensitivity S12 of the optical fiber temperature sensor is as follows:
  • M is the amplification factor of the conventional vernier effect
  • S 1 represents the temperature sensitivity of the Sagnac interferometer, where, B represents the birefringence coefficient, ⁇ B represents the change in the refractive index of the polarized fiber when the temperature increases by 1°C, ⁇ B ⁇ 0
  • S 2 represents the temperature sensitivity of the FP interferometer, where, ⁇ represents the thermo-optic coefficient of PDMS, ⁇ m represents the peak wavelength of the interference spectrum, n represents the refractive index of PDMS, and ⁇ is the thermal expansion coefficient of PDMS.
  • the PDMS cavity is a silica tube filled with PDMS or a hollow core fiber filled with PDMS.
  • one end of the single-mode optical fiber is connected to the attenuator, and the other end of the single-mode optical fiber is fused to one end of a quartz tube or a hollow-core optical fiber.
  • the fact that the first free spectral range and the second free spectral range are close but not equal includes: the difference between the first free spectral range and the second free spectral range accounts for the union of the first free spectral range and the second free spectral range; The set ratio is greater than the first preset value and less than the second preset value.
  • the first preset value is 1%; the second preset value is 10%.
  • a sensing head structure for an optical fiber temperature sensor comprising a first sensing interferometer and a second sensing interferometer, wherein the first sensing interferometer A sensing interferometer and the second sensing interferometer have opposite temperature responses; a first free spectrum range corresponding to the first sensing interferometer and a second free spectrum corresponding to the second sensing interferometer The ranges are close but not equal.
  • the first sensing interferometer includes a Sagnac interferometer composed of a second fiber coupler and a polarization fiber; the second sensing interferometer includes an F-P interferometer composed of a single-mode fiber and a PDMS cavity connected .
  • the superposition result of the interference spectrum of the Sagnac interferometer and the interference spectrum of the F-P interferometer is obtained by the spectrometer of the optical fiber temperature sensor, and the first end of the second optical fiber coupler is used for connecting to the The first fiber coupler of the fiber temperature sensor, the polarization fiber is connected between the second end and the third end of the second fiber coupler; wherein, the length of the polarization fiber is the same as the axial direction of the PDMS cavity The length is set such that the first free spectral range of the Sagnac interferometer is close to but not equal to the second free spectral range of the F-P interferometer.
  • the PDMS cavity is a silica tube filled with PDMS or a hollow core fiber filled with PDMS.
  • one end of the single-mode optical fiber is connected to the attenuator, and the other end of the single-mode optical fiber is spliced with one end of a quartz tube or a hollow-core optical fiber.
  • the fact that the first free spectral range and the second free spectral range are close but not equal includes: the difference between the first free spectral range and the second free spectral range accounts for the union of the first free spectral range and the second free spectral range; The set ratio is greater than the first preset value and less than the second preset value.
  • the first preset value is 1%; the second preset value is 10%.
  • a method for preparing a sensor head structure for a temperature sensor cascaded based on an optical fiber Sagnac interferometer and a PDMS cavity F-P interferometer comprising: taking a length of The first predetermined length of polarized fiber; the second end of the second fiber coupler is connected to one end of the segment of polarized fiber, and the third end of the second fiber coupler is connected to the other end of the segment of polarized fiber, so that the connected first The two-fiber coupler and the polarized fiber constitute a Sagnac interferometer; one end of the single-mode fiber is fused to one end of the hollow-core fiber or the silica tube; the other end of the hollow-core fiber or the silica tube is cut so that the cut hollow-core fiber or silica The length of the tube is the second predetermined length; the PDMS is filled into the cavity of the hollow-core optical fiber or the quartz tube, and the inside of the injected PDMS is
  • the fact that the first free spectral range and the second free spectral range are close but not equal includes: the difference between the first free spectral range and the second free spectral range accounts for the union of the first free spectral range and the second free spectral range; The set ratio is greater than the first preset value and less than the second preset value.
  • the first preset value is 1%; the second preset value is 10%.
  • the first sensing interferometer and the second sensing interferometer are cascaded, so that the free spectral ranges of the two are close but not equal, thereby Envelope the interference spectrum of the parallel double cavity of the first sensing interferometer and the second sensing interferometer.
  • a reference interferometer that is insensitive to the measured parameter and a sensing interferometer that is sensitive to external parameters are used; while in the embodiment of the present invention, two sensing interferometers that are both sensitive to temperature are used.
  • the two sensing interferometers have opposite responses to temperature, thereby realizing an enhanced vernier effect and improving the temperature measurement sensitivity compared with the prior art.
  • a high sensitivity temperature sensor cascading a fiber optic Sagnac ring (Sagnac interferometer) with a fiber optic PDMS cavity (Fabry-Perot interferometer), since the Sagnac ring and PDMS cavity have opposite temperature responses , by designing the free spectral ranges of the Sagnac ring and the PDMS cavity, the free spectral ranges of the optical fiber Sagnac ring and the optical fiber PDMS cavity in the sensor can be close but not equal, thereby enhancing the vernier effect and greatly improving the temperature measurement sensitivity.
  • FIG. 1 is a schematic structural diagram illustrating an example of an optical fiber temperature sensor according to an embodiment of the present invention
  • 2A is a schematic structural diagram illustrating a Sagnac interferometer composed of a second fiber coupler and a polarized fiber used in an embodiment of the present invention
  • 2B is a schematic structural diagram illustrating an F-P interferometer formed by connecting a single-mode fiber and a PDMS cavity used in an embodiment of the present invention
  • FIG. 3 is a schematic structural diagram illustrating another example of an optical fiber temperature sensor according to an embodiment of the present invention.
  • 4A is a schematic diagram showing the respective interference spectra of the Sagnac interferometer and the F-P interferometer employed in the embodiment of the present invention
  • 4B is a schematic diagram showing parallel interference spectra of the Sagnac interferometer and the F-P interferometer employed in the embodiment of the present invention.
  • the optical fiber temperature sensing is realized by cascading a reference interferometer that is not sensitive to the measured parameter and a sensing interferometer that is sensitive to the external parameter.
  • the performance of the optical fiber temperature sensor will be further improved.
  • the inventors found that by using two sensing interferometers with opposite temperature responses, an enhanced vernier effect can be achieved, so that the temperature measurement sensitivity can be further improved.
  • PDMS is an excellent heat-sensitive material, which has a strong thermal expansion and contraction effect under the action of temperature. After solidification, it is a colorless and transparent solid with good light transmission. In addition, PDMS has good adhesion and chemical inertness. Therefore, PDMS is very suitable for combination with optical fiber and can be used for high-sensitivity temperature measurement.
  • An embodiment of the present invention provides an optical fiber temperature sensor, the optical fiber temperature sensor includes a broad-spectrum light source, a first optical fiber coupler, a spectrometer, a first sensing interferometer, and a second sensing interferometer; wherein the first sensing interferometer A sensing interferometer and the second sensing interferometer have opposite temperature responses; a first free spectrum range corresponding to the first sensing interferometer and a second free spectrum corresponding to the second sensing interferometer The ranges are close but not equal.
  • FIG. 1 shows an exemplary structure of a fiber optic temperature sensor 100 .
  • the optical fiber temperature sensor 100 includes a broad-spectrum light source 101 , a spectrometer 102 , a first optical fiber coupler 103 , a first sensing interferometer 104 and a second sensing interferometer 105 .
  • the first sensing interferometer 104 and the second sensing interferometer 105 have opposite temperature responses.
  • the first free spectral range corresponding to the first sensing interferometer 104 is close to but not equal to the second free spectral range corresponding to the second sensing interferometer 105 .
  • the first free spectral range of the first sensing interferometer 104 is represented by FSR1
  • the second free spectral range of the second sensing interferometer 105 is represented by FSR2
  • the first free spectral range is close to the second free spectral range
  • unequal for example, means that the ratio of the difference between FSR1 and FSR2 to the union of FSR1 and FSR2 is larger than the first preset value and smaller than the second preset value.
  • the first preset value may be, for example, 0, or may be 1%, or may be other preset values.
  • the second preset value may be, for example, 10%, or may be 9%, or may be other preset values.
  • FSR1 can be 0.90-0.99 of FSR2, in this case, it can be understood that FSR2 covers FSR1, and FSR1 is the part of 90%-99% of FSR2, and FSR1 does not contain the other 10%-1% of FSR2 that part. In other words, FSR2 covers FSR1, and the width of FSR1 is about 0.90-0.99 times the width of FSR2.
  • FSR1 can also be 1.01 to 1.10 of FSR2.
  • FSR1 covers FSR2, and FSR1 is 101% to 110% of FSR2. That is to say, in the spectrum contained in FSR1, in addition to including In addition to all the spectra of FSR2, a part of the spectral range is additionally included, and the additional part of the width can account for 1% to 10% of the width of FSR2. In other words, FSR1 covers FSR2, and the width of FSR1 is 1.01-1.10 times that of FSR2.
  • FSR1 and FSR2 may be in a partially overlapping relationship, and the proportion of the overlapping part in the union of FSR1 and FSR2 may be, for example, 1% to 10%.
  • both the first and second preset values can be set according to empirical values, or can also be determined by an experimental method.
  • the first sensing interferometer 104 and the second sensing interferometer 105 are cascaded (parallel), and the two The free spectral ranges of , are close to but not equal, so that the interference spectrum of the parallel double cavity of the first sensing interferometer 104 and the second sensing interferometer 105 generates an envelope.
  • a reference interferometer that is insensitive to the measured parameter and a sensing interferometer that is sensitive to external parameters are used; while in the embodiment of the present invention, two sensing interferometers that are both sensitive to temperature are used.
  • the two sensing interferometers have opposite responses to temperature, thereby realizing an enhanced vernier effect and improving the temperature measurement sensitivity compared with the prior art.
  • the first sensing interferometer can be implemented by, for example, a Sagnac interferometer composed of a second fiber coupler and a polarization fiber, as shown in FIG. 2A .
  • the first end of the second fiber coupler (port 1 shown in FIG. 2A ) is used to connect the first fiber coupler, and the polarized fiber is connected to the second end of the second fiber coupler (port 2 shown in FIG. 2A ) and between the third end (port 3 shown in Figure 2A).
  • the second sensing interferometer can be realized by, for example, an F-P interferometer formed by connecting a single-mode fiber and a PDMS cavity, as shown in FIG. 2B . Wherein, the cavity of the PDMS cavity is filled with PDMS.
  • the PDMS cavity can be implemented using, for example, a PDMS-filled silica tube or a PDMS-filled hollow-core fiber.
  • One end of the single-mode fiber is used to connect the incident light (attenuator can be connected), and the other end is spliced with one end of the quartz tube or hollow-core fiber, so that the incoming incident light can be connected between the single-mode fiber and the hollow-core fiber. Reflection and transmission occur at the interface of the PDMS cavity.
  • FIG. 3 shows a schematic diagram of another possible structure of the optical fiber temperature sensor according to the embodiment of the present invention.
  • the broad-spectrum light source 301 , the spectrometer 302 , and the first fiber coupler 303 included in the optical fiber temperature sensor 300 may have the same characteristics as the broad-spectrum light source 101 , the spectrometer 102 , and the first fiber coupler 103 shown in FIG. 1 , respectively. structure, and can achieve similar functions, which will not be repeated here.
  • the fiber temperature sensor 300 in addition to a broad-spectrum light source 301 , a spectrometer 302 , and a first fiber coupler 303 , the fiber temperature sensor 300 also includes a fiber isolator 306 and an attenuator 307 .
  • the incident light output by the broad-spectrum light source 301 is divided into two paths after passing through the fiber isolator 306 and the first fiber coupler 303 in turn, one of which enters the Sagnac interferometer 304, and the other enters the F-P interferometer 305 through the attenuator 307.
  • the spectrometer 302 can obtain a superposition result (superposition spectrum) of the interference light spectrum returned by the Sagnac interferometer 304 and the interference light spectrum returned by the F-P interferometer 305 .
  • the incident light entering the Sagnac interferometer 304 is divided into two beams whose polarization directions are perpendicular to each other in the polarization fiber. After the polarization fiber, interference occurs between the two beams, and the obtained interference light is output from the first end of the second fiber coupler. Then, it is received by the spectrometer 302 through the first fiber coupler 303 .
  • the phases of the two beams of light in different polarization directions are different after passing through the polarized fiber, resulting in interference, and the above interference light is obtained.
  • the incident light entering the F-P interferometer 305 first enters the single-mode fiber, where a part of the light is reflected (reflected back to the single-mode fiber) at the interface M1 of the single-mode fiber and the PDMS cavity (as shown in FIG. 2B ), and the other part Light passes through this interface M1.
  • the other part of the light passing through the interface M1 enters the PDMS cavity and is partially reflected back to the single-mode fiber at the interface between the PDMS cavity and the air (the part of the light reflected at the interface between the PDMS cavity and the air first returns to the PDMS cavity, and passes through the PDMS cavity.
  • the cavity then enters the single-mode fiber through the interface M1), and interferes with the part of the light reflected back to the single-mode fiber at the interface M1 between the single-mode fiber and the PDMS cavity.
  • the length l of the polarizing fiber (the first predetermined length as described below) and the axial length d of the PDMS cavity (the second predetermined length as described below) are set such that the first free spectrum of the Sagnac interferometer The range is close to but not equal to the second free spectral range of the F-P interferometer.
  • the length l of the polarizing fiber and the axial length d of the PDMS cavity can be adjusted many times through experiments, so that the first free spectral range of the Sagnac interferometer related to the length l of the polarizing fiber and the axial length of the PDMS cavity are The second free spectral range of the F-P interferometer related to the length d The two free spectral ranges are close but not equal.
  • the temperature sensitivity S 12 of the optical fiber temperature sensor is shown in Equation 1.
  • M is the magnification factor of the conventional vernier effect.
  • S1 represents the temperature sensitivity of the Sagnac interferometer, where, B represents the birefringence coefficient, ⁇ B represents the change in the refractive index of the polarized fiber when the temperature increases by 1°C, ⁇ B ⁇ 0.
  • S2 represents the temperature sensitivity of the FP interferometer, where, ⁇ represents the thermo-optic coefficient of PDMS, ⁇ m represents the peak wavelength of the interference spectrum, n represents the refractive index of PDMS, and ⁇ is the thermal expansion coefficient of PDMS.
  • the conventional vernier effect requires a reference interferometer (insensitive to the measured parameter) and a sensing interferometer (sensitive to external parameters) in cascade, and the two interferometers in the sensor of this embodiment are both The sensor interferometer is used, and the two interferometers have opposite temperature responses to temperature, thereby realizing an enhanced vernier effect and further improving the temperature measurement sensitivity.
  • An embodiment of the present invention also provides a sensing head structure for an optical fiber temperature sensor, the sensing head structure includes a first sensing interferometer and a second sensing interferometer, wherein the first sensing interferometer and the The second sensing interferometer has an opposite temperature response; the first free spectral range corresponding to the first sensing interferometer is close to but not equal to the second free spectral range corresponding to the second sensing interferometer.
  • the sensing head structure of this embodiment includes a first sensing interferometer and a second sensing interferometer, wherein the first sensing interferometer and the second sensing interferometer have opposite temperature responses.
  • the first free spectral range corresponding to the first sensing interferometer is close to but not equal to the second free spectral range corresponding to the second sensing interferometer.
  • the first sensing interferometer includes, for example, a Sagnac interferometer composed of a second fiber coupler and a polarization fiber; as shown in FIG. 2B , the second sensing interferometer includes a single-mode fiber and a polarization fiber. F-P interferometer with PDMS cavity connected.
  • the PDMS cavity can be, for example, a silica tube filled with PDMS or a hollow-core fiber filled with PDMS.
  • the superposition result of the interference spectrum of the Sagnac interferometer and the interference spectrum of the F-P interferometer is obtained by the spectrometer of the fiber optic temperature sensor.
  • the first end of the second fiber coupler is used for connecting to the first fiber coupler of the fiber temperature sensor, and the polarized fiber is connected between the second end and the third end of the second fiber coupler.
  • the length of the polarizing fiber and the axial length of the PDMS cavity are set such that the first free spectral range of the Sagnac interferometer is close to but not equal to the second free spectral range of the F-P interferometer.
  • one end of the single-mode fiber is used to connect the attenuator, and the other end of the single-mode fiber is spliced with one end of a silica tube or hollow-core fiber.
  • the first free spectral range and the second free spectral range are close to but not equal, for example, means: the difference between the first free spectral range and the second free spectral range accounts for the union of the first free spectral range and the second free spectral range The ratio is greater than the first preset value and less than the second preset value.
  • the first preset value is, for example, 1%
  • the second preset value is, for example, 10%.
  • the structure of the sensor head of this embodiment can have the same function as the corresponding structure in the light temperature sensor in the exemplary device 1 described above, and can achieve similar effects, which will not be repeated here. .
  • An embodiment of the present invention also provides a method for preparing a sensor head structure for a temperature sensor cascaded based on an optical fiber Sagnac interferometer and an F-P interferometer. ; Connect the second end of the second fiber coupler to one end of the polarization fiber, and connect the third end of the second fiber coupler to the other end of the polarization fiber, so that the connected second fiber coupler and the polarization fiber Constitute the Sagnac interferometer; splicing one end of the single-mode fiber with one end of the PDMS cavity, the PDMS cavity is a hollow-core fiber or a silica tube; cutting the other end of the PDMS cavity, so that the length of the cut hollow-core fiber or silica tube is The second predetermined length; filling the cavity of the hollow-core optical fiber or quartz tube with PDMS, and making the inside of the injected PDMS free of air bubbles, and then heating to solidify the injected PDMS to form an F-P interferometer; wherein, the first
  • two preparation sub-flows are included, namely the Sagnac interferometer preparation sub-flow and the F-P interferometer preparation sub-flow.
  • the preparation sub-process of the Sagnac interferometer take a section of polarized fiber with a length of the first predetermined length, connect the second end of the second fiber coupler to one end of the polarized fiber, and then connect the third end of the second fiber coupler The other end of the polarization fiber is connected, so that the connected second fiber coupler and the polarization fiber constitute a Sagnac interferometer.
  • one end of the single-mode fiber is fused to one end of the hollow-core fiber or the quartz tube. Then, the other end of the hollow-core optical fiber or the quartz tube is cut, so that the length of the cut hollow-core optical fiber or the quartz tube is a second predetermined length. Next, the cavity of the hollow-core optical fiber or the quartz tube is filled with PDMS, and the inside of the injected PDMS is free of air bubbles, and then heated to solidify the injected PDMS to form an F-P interferometer.
  • the first predetermined length and the second predetermined length satisfy: the first free spectral range of the Sagnac interferometer is close to but not equal to the second free spectral range of the F-P interferometer.
  • the first free spectral range and the second free spectral range are close to but not equal, for example, including: the difference between the first free spectral range and the second free spectral range accounts for the sum of the first free spectral range and the second free spectral range
  • the set ratio is greater than the first preset value and less than the second preset value.
  • the first preset value is, for example, 1%; the second preset value is, for example, 10%.
  • the sensor structure is shown in Figure 3. It consists of a broad-spectrum light source (1200nm-1600nm), a fiber isolator, a first fiber coupler, a fiber attenuator (ie, the attenuator in the figure), Sagnac ring (ie, 304 in the figure), The PDMS cavity F-P interferometer (ie, 305 in the figure) is composed of a spectrometer.
  • the Sagnac ring is composed of two ports of the second fiber coupler connecting the two ends of a length of L-polarized fiber respectively;
  • the PDMS cavity is composed of a single-mode fiber spliced with a section of silica tube or hollow-core fiber, and then PDMS is filled with silica tube or hollow-core fiber.
  • the diameter of the single-mode fiber and the polarizing fiber is, for example, 125 microns, and the core diameter is, for example, 8-10 microns; the outer diameter of the hollow-core fiber is, for example, 125 microns, and the inner diameter is, for example, 50-70 microns
  • the sensor head part includes two sensor heads, wherein the preparation process of the Sagnac ring is shown in Figure 2A: the two ends 2 and 3 of the second optical fiber coupler are respectively connected to the two ends of the polarized optical fiber of length L to form,
  • the length L of the polarizing fiber ensures that the free spectral range of the Sagnac ring is close to but not equal to that of the PDMS cavity.
  • FIG. 2B The fabrication process of another sensor head is shown in Figure 2B, for example: the single-mode fiber is spliced with the hollow-core fiber, and the hollow-core fiber is cut. After cutting, the length of the hollow-core is d to ensure the free spectral range of the PDMS cavity and the free spectrum of the Sagnac ring. The ranges are close but not equal; fill the hollow core fiber with PDMS to ensure that there are no air bubbles inside, and then heat to solidify the PDMS to form a PDMS cavity.
  • the sensor head containing the PDMS cavity can be prepared first, and then the sensor head corresponding to the Sagnac ring is prepared.
  • d takes a value in the range of [100um, 300um].
  • the selection of d cannot be too long, otherwise, the light loss will be too large, and it is difficult to interfere.
  • the hollow-core optical fiber of length d is cut, and PDMS is injected according to the method described above, and a PDMS cavity is formed after curing. In this way, d is determined, that is, the free spectral range of the PDMS cavity is determined.
  • an appropriate value of L is selected so that the free spectral range of the prepared Sagnac ring is close to but not equal to the free spectral range of PDMS, for example, one of the two free spectral ranges covers the other.
  • One spectral range, and one spectral range is 1.01 to 1.10 times or 0.90 to 0.99 times larger than the other spectral range.
  • L can take a value of 1m. It should be understood that the value of L is not limited to the values mentioned in the above examples. According to the previously determined d, the actual value of L is determined by satisfying the condition that "the free spectral range of the Sagnac ring is close to but not equal to the free spectral range of PDMS".
  • the incident light from the broadband light source is divided into two paths through the fiber isolator and the first fiber coupler in turn, one path enters the Sagnac ring, and the other path enters the PDMS cavity F-P interferometer through the attenuator.
  • the incident light entering the Sagnac ring is divided into two beams whose polarization directions are perpendicular to each other in the polarization fiber. Due to the different refractive indices in the two polarization directions, interference occurs between the two polarization components with phase differences after passing through the polarization fiber. , the interference light is output from the first section of the second fiber coupler and then received by the spectrometer through the first fiber coupler.
  • the incident light entering the PDMS cavity F-P interferometer is at the interface M1, part of the light is reflected back to the single-mode fiber, the other part of the light is transmitted into the PDMS cavity, and then a part of the light is reflected back to the single-mode fiber by the interface M2.
  • the interference spectrum of the Sagnac ring and the PDMS cavity can be expressed as
  • ⁇ is the wavelength of incident light
  • I 1 ( ⁇ ) represents the intensity of the interference spectrum of the Sagnac ring
  • I 2 ( ⁇ ) represents the intensity of the interference spectrum of the PDMS cavity FP interferometer
  • A1 represents the interference spectrum amplitude of the Sagnac ring
  • A2 represents the interference spectrum amplitude of the PDMS cavity FP interferometer
  • n is the refractive index of PDMS, and its value is about 1.40
  • B is the birefringence coefficient, and its value is 3 ⁇ 10 -4 .
  • the Sagnac ring and the PDMS cavity FP interferometer form a parallel structure, and the spectrum received by the spectrometer is the superposition of the Sagnac ring and the PDMS cavity FP interferometer.
  • 4A is a schematic diagram showing the interference spectrum of the Sagnac interferometer and the interference spectrum of the F-P interferometer. Among them, the ordinate is the light intensity, the abscissa is the wavelength, the FSI is the Sagnac interferometer, and the FPI is the F-P interferometer.
  • this envelope can be expressed as
  • I envelope ( ⁇ ) represents the spectral intensity of the above-mentioned interference spectrum envelope
  • E is the amplitude of the interference spectrum envelope
  • M is the amplification factor of the conventional vernier effect.
  • the temperature sensitivity S1 of the Sagnac ring can be expressed as
  • ⁇ B is the change in the refractive index of the polarized fiber when the temperature increases by 1°C, and ⁇ B ⁇ 0.
  • the temperature sensitivity S2 of the PDMS cavity can be expressed as
  • ⁇ represents the thermo-optic coefficient of PDMS
  • ⁇ m represents the peak wavelength of the interference spectrum
  • ⁇ is the thermal expansion coefficient of PDMS, and its value is about 9.6 ⁇ 10 -4 /°C.
  • S 1 ⁇ 0 and S 2 >0 are positive values, that is, when the temperature changes, the frequency shift directions of the Sagnac ring and the PDMS cavity interference spectrum are opposite.
  • the interference spectrum will generate an envelope after parallel connection, and the shift of the interference spectrum envelope with temperature will be much larger than that of a single Sagnac ring and a single PDMS cavity, and its sensitivity S 12 for
  • the temperature sensor proposed in this embodiment realizes the enhanced vernier effect, and the temperature sensitivity is higher than the sensitivity of a single Sagnac ring and a single PDMS cavity by M 1 ′ and M 2 ′ respectively. Both M 1 ′ and M 2 ′ are significantly larger than the conventional vernier effect magnification M.
  • 201810738431.6 adopts the method of coating and gluing to make the optical fiber microcavity, the preparation process is complicated, the coating requires expensive coating equipment, and it takes a long time, and the gluing method The stability of the sensor is deteriorated; this patent adopts the optical fiber fusion method to prepare the optical fiber microcavity, which is easy to operate and does not require expensive equipment.
  • this embodiment has the following advantages: 1) only the optical fiber fusion splicing method is used, which is simple to manufacture and does not require expensive special equipment; 2) does not require gluing, and the sensor has good stability; 3) double-cavity parallel connection can produce The vernier effect can improve the sensitivity, and the extinction ratio of the interference spectrum envelope can be adjusted; 4) an enhanced vernier effect is produced, and the sensitivity magnification is higher.

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Abstract

本发明提供了一种光纤温度传感器、传感头结构及制备方法。光纤温度传感器包括宽谱光源、第一光纤耦合器、光谱仪、第一传感干涉计以及第二传感干涉计；其中，所述第一传感干涉计与所述第二传感干涉计具有相反的温度响应；所述第一传感干涉计对应的第一自由光谱范围与所述第二传感干涉计对应的第二自由光谱范围接近但不相等。在本发明的上述技术中，采用对温度均敏感的两个传感干涉计，且这两个传感干涉计对温度的响应是相反的，从而实现了增强型游标效应，相比现有技术提高了温度测量灵敏度。

Description

光纤温度传感器及传感头结构 技术领域
本发明的实施方式涉及光纤传感领域，更具体地，本发明的实施方式涉及一种光纤温度传感器、传感头结构及制备方法。
背景技术
温度作为国际单位制七个基本物理量之一，在国民经济、国防建设和科学研究等领域中温度的准确测量具有举足轻重的作用。随着温度传感应用需求的提高，传统的温度传感器已经无法满足高精度的测量要求。光纤温度传感器具有尺寸小、测量精度高、灵敏度高、抗电磁干扰强、电绝缘性好、温度范围大等诸多优点，在温度测量方面有着自身独特的优势。
发明内容
在本上下文中，本发明的实施方式期望提供一种光纤温度传感器、传感头结构及制备方法，以进一步提高光纤温度传感器的温度测量灵敏度。
在本发明实施方式的第一方面中，提供了一种光纤温度传感器，所述光纤温度传感器包括宽谱光源、第一光纤耦合器、光谱仪、第一传感干涉计以及第二传感干涉计；其中，所述第一传感干涉计与所述第二传感干涉计具有相反的温度响应；所述第一传感干涉计对应的第一自由光谱范围与所述第二传感干涉计对应的第二自由光谱范围接近但不相等。
进一步地，根据权利要求1所述的光纤温度传感器，所述第一传感干涉计包括由第二光纤耦合器和偏振光纤构成的萨格纳克(Sagnac)干涉计；所述第二传感干涉计包括由单模光纤和聚二甲基硅氧烷(PDMS)腔连接而成的F-P干涉计。
进一步地，还包括光纤隔离器和衰减器；所述宽谱光源输出的入射光依次经所述光纤隔离器和所述第一光纤耦合器后分为两路，其中一路进入所述Sagnac干涉计，另一路经所述衰减器进入所述F-P干涉计，通过所述光谱仪获得由所述Sagnac干涉计返回的干涉谱与由所述F-P干涉计返回的干涉谱的 叠加结果；所述第二光纤耦合器的第一端连接至所述第一光纤耦合器，所述偏振光纤连接于所述第二光纤耦合器的第二端和第三端之间，进入所述Sagnac干涉计的入射光在所述偏振光纤内分为偏振方向相互垂直的两束光束，经所述偏振光纤后两光束之间发生干涉，得到的干涉光从第二光纤耦合器的第一端输出后再经第一光纤耦合器而被光谱仪接收；进入所述F-P干涉计的入射光的一部分光被所述单模光纤与所述PDMS腔的界面处反射回所述单模光纤，另一部分光透射进入所述PDMS腔后被所述PDMS腔与空气的界面处部分反射回所述单模光纤后，与被所述单模光纤与所述PDMS腔的界面处反射回所述单模光纤的所述一部分光干涉；其中，所述偏振光纤的长度与所述PDMS腔的轴向长度被设置成：使得所述Sagnac干涉计的第一自由光谱范围与所述F-P干涉计的第二自由光谱范围接近但不相等。
进一步地，所述光纤温度传感器的温度灵敏度S 12如下：
Figure PCTCN2022082610-appb-000001
其中，
Figure PCTCN2022082610-appb-000002
M为常规游标效应的放大因子；S 1表示Sagnac干涉计的温度灵敏度，其中，
Figure PCTCN2022082610-appb-000003
B表示双折射系数，ΔB表示温度升高1℃时偏振光纤折射率的变化量，ΔB<0；S 2表示F-P干涉计的温度灵敏度，其中，
Figure PCTCN2022082610-appb-000004
α表示PDMS的热光系数，λ m表示干涉谱峰值波长，n表示PDMS的折射率，β为PDMS的热膨胀系数。
进一步地，所述PDMS腔为填充有PDMS的石英管或填充有PDMS的空芯光纤。
进一步地，所述单模光纤的一端连接所述衰减器，所述单模光纤的另一 端与石英管或空芯光纤的一端熔接。
进一步地，第一自由光谱范围与第二自由光谱范围接近但不相等包括：第一自由光谱范围与第二自由光谱范围之间的差异部分占第一自由光谱范围与第二自由光谱范围的并集之比大于第一预设值、且小于第二预设值。
进一步地，所述第一预设值为1％；所述第二预设值为10％。
根据本发明的第二方面，还提供了一种用于光纤温度传感器的传感头结构，所述传感头结构包括第一传感干涉计以及第二传感干涉计，其中，所述第一传感干涉计与所述第二传感干涉计具有相反的温度响应；所述第一传感干涉计对应的第一自由光谱范围与所述第二传感干涉计对应的第二自由光谱范围接近但不相等。
进一步地，所述第一传感干涉计包括由第二光纤耦合器和偏振光纤构成的Sagnac干涉计；所述第二传感干涉计包括由单模光纤和PDMS腔连接而成的F-P干涉计。
进一步地，所述Sagnac干涉计的干涉谱与所述F-P干涉计的干涉谱的叠加结果由所述光纤温度传感器的光谱仪获得，所述第二光纤耦合器的第一端用于连接至所述光纤温度传感器的第一光纤耦合器，所述偏振光纤连接于所述第二光纤耦合器的第二端和第三端之间；其中，所述偏振光纤的长度与所述PDMS腔的轴向长度被设置成：使得所述Sagnac干涉计的第一自由光谱范围与所述F-P干涉计的第二自由光谱范围接近但不相等。
进一步地，所述PDMS腔为填充有PDMS的石英管或填充有PDMS的空芯光纤。
进一步地，所述单模光纤的一端连接所述衰减器，所述单模光纤的另一端与石英管或空芯光纤的一端熔接。
进一步地，第一自由光谱范围与第二自由光谱范围接近但不相等包括：第一自由光谱范围与第二自由光谱范围之间的差异部分占第一自由光谱范围与第二自由光谱范围的并集之比大于第一预设值、且小于第二预设值。
进一步地，所述第一预设值为1％；所述第二预设值为10％。
根据本发明的第三方面，还提供了一种用于基于光纤Sagnac干涉计和PDMS腔F-P干涉计级联的温度传感器的传感头结构的制备方法，所述制备 方法包括：取一段长度为第一预定长度的偏振光纤；将第二光纤耦合器的第二端连接该段偏振光纤的一端，将第二光纤耦合器的第三端连接该段偏振光纤的另一端，使得相连接的第二光纤耦合器与偏振光纤构成Sagnac干涉计；将单模光纤的一端与空芯光纤或石英管的一端熔接；切割该空芯光纤或石英管的另一端，使得切割后的空芯光纤或石英管的长度为第二预定长度；将PDMS注满空芯光纤或石英管的腔内，并使注入的PDMS内部无气泡，然后加热使注入的PDMS固化，形成PDMS腔；其中，第一预定长度和第二预定长度满足：使得所述Sagnac干涉计的第一自由光谱范围与所述F-P干涉计的第二自由光谱范围接近但不相等。
进一步地，第一自由光谱范围与第二自由光谱范围接近但不相等包括：第一自由光谱范围与第二自由光谱范围之间的差异部分占第一自由光谱范围与第二自由光谱范围的并集之比大于第一预设值、且小于第二预设值。
进一步地，所述第一预设值为1％；所述第二预设值为10％。
根据本发明实施方式的一种光纤温度传感器、传感头结构及制备方法，通过第一传感干涉计与第二传感干涉计级联，令二者的自由光谱范围接近但不相等，从而使第一传感干涉计与第二传感干涉计的并联双腔的干涉谱产生包络。常规的游标效应中，采用一个对被测参量不敏感的参考干涉计和一个对外界参量敏感的传感干涉计；而在本发明的实施例中，采用对温度均敏感的两个传感干涉计，且这两个传感干涉计对温度的响应是相反的，从而实现了增强型游标效应，相比现有技术提高了温度测量灵敏度。
在一些实施例中，能够提供将光纤Sagnac环(Sagnac干涉计)与光纤PDMS腔(法布里-珀罗干涉计)级联的高灵敏度温度传感器，由于Sagnac环和PDMS腔具有相反的温度响应，通过设计Sagnac环和PDMS腔的自由光谱范围，能够使该传感器中光纤Sagnac环和光纤PDMS腔的自由光谱范围接近但不相等，从而增强型游标效应，大幅提高温度测量灵敏度。
附图说明
本发明可以通过参考下文中结合附图所给出的描述而得到更好的理解，其中在所有附图中使用了相同或相似的附图标记来表示相同或者相似的部件。所 述附图连同下面的详细说明一起包含在本说明书中并且形成本说明书的一部分，而且用来进一步举例说明本发明的优选实施例和解释本发明的原理和优点。其中：
图1是示出根据本发明实施例的光纤温度传感器的一个示例的结构示意图；
图2A是示出本发明的实施例所采用的由第二光纤耦合器和偏振光纤构成的Sagnac干涉计的结构示意图；
图2B是示出本发明的实施例所采用的由单模光纤和PDMS腔连接而成的F-P干涉计的结构示意图；
图3是示出根据本发明实施例的光纤温度传感器的另一个示例的结构示意图；
图4A是示出本发明的实施例所采用的Sagnac干涉计以及F-P干涉计各自的干涉谱的示意图；
图4B是示出本发明的实施例所采用的Sagnac干涉计以及F-P干涉计的并联干涉谱的示意图。
本领域技术人员应当理解，附图中的元件仅仅是为了简单和清楚起见而示出的，而且不一定是按比例绘制的。例如，附图中某些元件的尺寸可能相对于其他元件放大了，以便有助于提高对本发明实施例的理解。
具体实施方式
在下文中将结合附图对本发明的示范性实施例进行描述。为了清楚和简明起见，在说明书中并未描述实际实施方式的所有特征。然而，应该了解，在开发任何这种实际实施例的过程中必须做出很多特定于实施方式的决定，以便实现开发人员的具体目标，例如，符合与***及业务相关的那些限制条件，并且这些限制条件可能会随着实施方式的不同而有所改变。此外，还应该了解，虽然开发工作有可能是非常复杂和费时的，但对得益于本发明内容的本领域技术人员来说，这种开发工作仅仅是例行的任务。
在此，还需要说明的一点是，为了避免因不必要的细节而模糊了本发明，在附图中仅仅示出了与根据本发明的方案密切相关的装置结构和/或处理步骤，而省略了与本发明关系不大的其他细节。
本发明人发现，在常规的游标效应中，通过对被测参量不敏感的参考干涉计和对外界参量敏感的传感干涉计相级联，实现光纤温度传感。
若能进一步提高温度测量的灵敏度，这将使得光纤温度传感器的性能得到进一步的改善。
本发明人发现，采用具有相反温度响应的两个传感干涉计，能够实现增强型游标效应，从而能够进一步提高温度测量灵敏度。
此外，本发明人还发现，PDMS是一种非常出色的热敏材料，在温度的作用下会有很强的热胀冷缩效应，凝固后为无色透明的固体，具有很好的透光性和折光性，此外，PDMS还具有良好的粘接性和化学惰性。因此，PDMS非常适合与光纤相结合，能够用于高灵敏度温度测量。
下面，分别描述本发明的一些实施例。
示例性装置1
本发明的实施例提供了一种光纤温度传感器，所述光纤温度传感器包括宽谱光源、第一光纤耦合器、光谱仪、第一传感干涉计以及第二传感干涉计；其中，所述第一传感干涉计与所述第二传感干涉计具有相反的温度响应；所述第一传感干涉计对应的第一自由光谱范围与所述第二传感干涉计对应的第二自由光谱范围接近但不相等。
下面，描述本发明的光纤温度传感器的一个示例。
图1示出了光纤温度传感器100的一种示例性结构。
如图1所示，光纤温度传感器100包括宽谱光源101、光谱仪102、第一光纤耦合器103、第一传感干涉计104以及第二传感干涉计105。
其中，第一传感干涉计104与第二传感干涉计105具有相反的温度响应。
第一传感干涉计104对应的第一自由光谱范围与第二传感干涉计105对应的第二自由光谱范围接近但不相等。
作为示例，用FSR1表示第一传感干涉计104的第一自由光谱范围，用FSR2表示第二传感干涉计105的第二自由光谱范围，则第一自由光谱范围与第二自由光谱范围接近但不相等例如是指：FSR1与FSR2之间的差异部分占FSR1与FSR2的并集之比要大于第一预设值、并且小于第二预设值。
其中，第一预设值例如可以为0，或者可以为1％，或者也可以是其他预设数值。第二预设值例如可以为10％，或者可以为9％，或者也可以是其他预设数值。
例如，FSR1可以是FSR2的0.90～0.99，这种情况下，可以理解为FSR2覆盖FSR1，而FSR1是FSR2的90％～99％的那部分，且FSR1并不包含FSR2的另外10％～1％的那部分。换句话说，FSR2覆盖了FSR1，且FSR1的宽度约为FSR2的宽度的0.90～0.99倍。
又如，FSR1也可以是FSR2的1.01～1.10，这种情况下，可以理解为FSR1覆盖FSR2，而FSR1是FSR2的101％～110％，也就是说，在FSR1所包含的光谱中，除了包括所有FSR2的光谱之外，还额外包括了一部分光谱范围，额外的这部分宽度可以占FSR2宽度的1％～10％。换句话说，FSR1覆盖了FSR2，且FSR1的宽度是FSR2的宽度的1.01～1.10倍。
或者，FSR1与FSR2也可以是部分重叠的关系，而重叠的部分在FSR1与FSR2的并集中的占比例如可以是1％～10％。
应当说明的是，第一、第二预设值均可以根据经验值来设定，或者也可以通过试验的方法确定。
由此，在实际应用中，当利用本发明实施例的上述光纤温度传感器进行温度传感测量时，通过第一传感干涉计104与第二传感干涉计105级联(并联)，二者的自由光谱范围接近但不相等，从而使得第一传感干涉计104与第二传感干涉计105的并联双腔的干涉谱产生包络。
常规的游标效应中，采用一个对被测参量不敏感的参考干涉计和一个对外界参量敏感的传感干涉计；而在本发明的实施例中，采用对温度均敏感的两个传感干涉计，且这两个传感干涉计对温度的响应是相反的，从而实现了增强型游标效应，相比现有技术提高了温度测量灵敏度。
作为示例，第一传感干涉计例如可以采用由第二光纤耦合器和偏振光纤构成的Sagnac干涉计实现，如图2A所示。第二光纤耦合器的第一端(图2A所示的端口1)用于连接第一光纤耦合器，偏振光纤连接于第二光纤耦合器的第二端(图2A所示的端口2)和第三端(图2A所示的端口3)之间。
此外，第二传感干涉计例如可以采用由单模光纤和PDMS腔连接而成的 F-P干涉计来实现，如图2B所示。其中，上述PDMS腔的腔内填充有PDMS。
作为示例，PDMS腔例如可以采用填充有PDMS的石英管或填充有PDMS的空芯光纤实现。
单模光纤的一端是用于接入入射光的(可以连接衰减器)，而其另一端与石英管或空芯光纤的一端熔接，使得接入的入射光能够在单模光纤与空芯光纤的PDMS腔的界面处发生反射和透射。
图3示出了本发明实施例的光纤温度传感器的另一种可能的结构的示意图。
在图3中，光纤温度传感器300包括的宽谱光源301、光谱仪302、第一光纤耦合器303可以分别具有与图1所示的宽谱光源101、光谱仪102、第一光纤耦合器103相同的结构，并能够达到相类似的功能，这里不再赘述。
如图3所示，光纤温度传感器300除了包括宽谱光源301、光谱仪302、第一光纤耦合器303之外，还包括光纤隔离器306和衰减器307。
宽谱光源301输出的入射光依次经光纤隔离器306和第一光纤耦合器303后分为两路，其中一路进入Sagnac干涉计304，另一路经衰减器307进入F-P干涉计305，这样，通过光谱仪302能够获得由Sagnac干涉计304返回的干涉光光谱与由F-P干涉计305返回的干涉光光谱的叠加结果(叠加谱)。
进入Sagnac干涉计304的入射光在偏振光纤内分为偏振方向相互垂直的两束光束，经偏振光纤后两光束之间发生干涉，得到的干涉光从第二光纤耦合器的第一端输出后再经第一光纤耦合器303而被光谱仪302接收。
在Sagnac环中，由于两种偏振方向的折射率不同，经偏振光纤后两束光之间不同偏振方向的相位不同，从而产生干涉，得到上述干涉光。
此外，进入F-P干涉计305的入射光首先进入单模光纤，其中一部分光在单模光纤与PDMS腔的界面M1(如图2B所示)处发生反射(被反射回单模光纤)、另一部分光透过该界面M1。
透过界面M1的上述另一部分光进入PDMS腔内被PDMS腔与空气的界面处部分反射回单模光纤后(被PDMS腔与空气的界面处反射的这部分光先是返回到PDMS腔，经PDMS腔后再透过界面M1进入单模光纤)，与被单模光纤与PDMS腔的界面M1处反射回单模光纤的那部分光发生干涉。
其中，偏振光纤的长度l(如下文所述的第一预定长度)与PDMS腔的轴向长度d(如下文所述的第二预定长度)被设置成：使得Sagnac干涉计的第一自由光谱范围与F-P干涉计的第二自由光谱范围接近但不相等。
例如可以通过试验的方法，多次调整偏振光纤的长度l以及PDMS腔的轴向长度d，以使得与偏振光纤的长度l有关的Sagnac干涉计的第一自由光谱范围以及与PDMS腔的轴向长度d有关的F-P干涉计的第二自由光谱范围这二个自由光谱范围接近但不相等。
作为示例，光纤温度传感器的温度灵敏度S 12如公式一所示。
公式一：
Figure PCTCN2022082610-appb-000005
其中，
Figure PCTCN2022082610-appb-000006
M为常规游标效应的放大因子。
S 1表示Sagnac干涉计的温度灵敏度，其中，
Figure PCTCN2022082610-appb-000007
B表示双折射系数，ΔB表示温度升高1℃时偏振光纤折射率的变化量，ΔB<0。
S 2表示F-P干涉计的温度灵敏度，其中，
Figure PCTCN2022082610-appb-000008
α表示PDMS的热光系数，λ m表示干涉谱峰值波长，n表示PDMS的折射率，β为PDMS的热膨胀系数。
这样，通过将光纤Sagnac环(Sagnac干涉计)与光纤PDMS腔(法布里-珀罗干涉计)级联的高灵敏度温度传感器，该传感器中光纤Sagnac环和光纤PDMS腔的自由光谱范围接近但不相等，从而产生游标效应来提高温度测量灵敏度。不同于常规游标效应，常规游标效应需要一个参考干涉计(对被测参量不敏感)和一个传感干涉计(对外界参量敏感)级联，而本实施例的传感器中 两个干涉计均为传感干涉计，且两干涉计对温度具有相反的温度响应，从而实现了增强型游标效应，进一步提高了温度测量灵敏度。
示例性装置2
本发明的实施例还提供了一种用于光纤温度传感器的传感头结构，该传感头结构包括第一传感干涉计以及第二传感干涉计，其中，第一传感干涉计与第二传感干涉计具有相反的温度响应；第一传感干涉计对应的第一自由光谱范围与第二传感干涉计对应的第二自由光谱范围接近但不相等。
本实施例的传感头结构包括第一传感干涉计以及第二传感干涉计，其中，第一传感干涉计与第二传感干涉计具有相反的温度响应。
第一传感干涉计对应的第一自由光谱范围与第二传感干涉计对应的第二自由光谱范围接近但不相等。
作为示例，如图2A所示，第一传感干涉计例如包括由第二光纤耦合器和偏振光纤构成的Sagnac干涉计；如图2B所示，第二传感干涉计包括由单模光纤和PDMS腔连接而成的F-P干涉计。
其中，PDMS腔例如可以为填充有PDMS的石英管或填充有PDMS的空芯光纤。
作为示例，Sagnac干涉计的干涉谱与F-P干涉计的干涉谱的叠加结果由光纤温度传感器的光谱仪获得。
第二光纤耦合器的第一端用于连接至光纤温度传感器的第一光纤耦合器，偏振光纤连接于第二光纤耦合器的第二端和第三端之间。
其中，偏振光纤的长度与PDMS腔的轴向长度被设置成：使得Sagnac干涉计的第一自由光谱范围与F-P干涉计的第二自由光谱范围接近但不相等。
例如，单模光纤的一端用于连接衰减器，而单模光纤的另一端则与石英管或空芯光纤的一端熔接。
第一自由光谱范围与第二自由光谱范围接近但不相等例如是指：第一自由光谱范围与第二自由光谱范围之间的差异部分占第一自由光谱范围与第二自由光谱范围的并集之比大于第一预设值、且小于第二预设值。
作为示例，第一预设值例如为1％，第二预设值例如为10％。
需要说明的是，本实施例的传感头结构例如可以具有与上文描述的示例性装置1中的光线温度传感器中的对应结构相同的功能，并能够达到相类似的效果，这里不再赘述。
示例性方法
本发明的实施例还提供了一种用于基于光纤Sagnac干涉计和F-P干涉计级联的温度传感器的传感头结构的制备方法，制备方法包括：取一段长度为第一预定长度的偏振光纤；将第二光纤耦合器的第二端连接该段偏振光纤的一端，将第二光纤耦合器的第三端连接该段偏振光纤的另一端，使得相连接的第二光纤耦合器与偏振光纤构成Sagnac干涉计；将单模光纤的一端与PDMS腔的一端熔接，该PDMS腔为空芯光纤或石英管；切割该PDMS腔的另一端，使得切割后的空芯光纤或石英管的长度为第二预定长度；将PDMS注满空芯光纤或石英管的腔内，并使注入的PDMS内部无气泡，然后加热使注入的PDMS固化，形成F-P干涉计；其中，第一预定长度和第二预定长度满足：使得Sagnac干涉计的第一自由光谱范围与F-P干涉计的第二自由光谱范围接近但不相等。
下面描述上述制备方法的一个实施例。
在该实施例中，包括两个制备子流程，即Sagnac干涉计制备子流程和F-P干涉计制备子流程。
应当理解的是，这两个子流程不限于以下描述的顺序执行，也可以调换，或者并行进行。
在Sagnac干涉计制备子流程中，取一段长度为第一预定长度的偏振光纤，将第二光纤耦合器的第二端连接该段偏振光纤的一端，再将第二光纤耦合器的第三端连接该段偏振光纤的另一端，使得相连接的第二光纤耦合器与偏振光纤构成Sagnac干涉计。
在F-P干涉计制备子流程中，将单模光纤的一端与空芯光纤或石英管的一端熔接。然后，切割该空芯光纤或石英管的另一端，使得切割后的空芯光纤或石英管的长度为第二预定长度。接着，将PDMS注满空芯光纤或石英管的腔内，并使注入的PDMS内部无气泡，然后加热使注入的PDMS固化， 形成F-P干涉计。
其中，第一预定长度和第二预定长度满足：使得Sagnac干涉计的第一自由光谱范围与F-P干涉计的第二自由光谱范围接近但不相等。
其中，第一自由光谱范围与第二自由光谱范围接近但不相等例如包括：第一自由光谱范围与第二自由光谱范围之间的差异部分占第一自由光谱范围与第二自由光谱范围的并集之比大于第一预设值、且小于第二预设值。
作为示例，第一预设值例如为1％；第二预设值例如为10％。
优选实施例
传感器结构如图3所示，由宽谱光源(1200nm-1600nm)、光纤隔离器、第一光纤耦合器、光纤衰减器(即图中的衰减器)、Sagnac环(即图中的304)、PDMS腔F-P干涉计(即图中的305)和光谱仪构成。
Sagnac环由第二光纤耦合器的两个端口分别连接一段长度为L偏振光纤的两端构成；PDMS腔由单模光纤熔接一段石英管或空芯光纤，然后PDMS填充石英管或空芯光纤构成。
其中，单模光纤和偏振光纤的直径例如均为125微米，纤芯直径例如均为8-10微米；空芯光纤外径例如为125微米，内径例如为50-70微米
传感头部分包括两个传感头，其中，Sagnac环的制备过程如图2A所示：将第二光纤耦合器的两端2和3分别于长度为L的偏振光纤的两端连接构成，偏振光纤的长度L保证Sagnac环的自由光谱范围与PDMS腔的自由光谱范围接近但不相等。
另一个传感头的制备过程例如如图2B所示：将单模光纤与空芯光纤熔接，切割空芯光纤，切割后空芯长度为d保证PDMS腔的自由光谱范围与Sagnac环的自由光谱范围接近但不相等；将PDMS注满空芯光纤，保证内部无气泡，然后加热使PDMS固化，形成PDMS腔。
在该优选实施例中，传感头的制备过程中，可以先制备含有PDMS腔的传感头，再制备Sagnac环对应的传感头。
这样，首先确定d的长度范围，例如d在[100um,300um]范围内取值。其中，d的选取不能选取过长，否则会造成光损耗过大，难以发生干涉。
在将单模光纤与空心光纤熔接之后，切割长度为d的空芯光纤后，按照上文所述方法注入PDMS，固化后形成PDMS腔。这样，确定了d，也即PDMS腔的自由光谱范围确定了。
接着，在d确定了之后，再选取合适的L值，使得制备的Sagnac环的自由光谱范围与PDMS的自由光谱范围接近但不相等，例如使这二个自由光谱范围中的一个光谱范围覆盖另一个光谱范围，且一个光谱范围是另一个光谱范围的1.01～1.10倍或者0.90～0.99倍。例如，在本实施例中，L可取值为1m。应当理解的是，L的取值不限于上述例子所说数值。根据先确定的d，通过使得“Sagnac环的自由光谱范围与PDMS的自由光谱范围接近但不相等”这个条件满足而确定实际的L的值。
光束传输过程及传感原理：
如图3所示，宽带光源发出的入射光依次经光纤隔离器和第一光纤耦合器后分两路，一路进入Sagnac环，另一路经衰减器进入PDMS腔F-P干涉计。进入Sagnac环的入射光在偏振光纤内分为偏振方向相互垂直的两束光束，由于两种偏振方向上的折射率不同，经偏振光纤后具有相位差的两种偏振分量的光束之间发生干涉，干涉光从第二光纤耦合器的第一段输出后再经第一光纤耦合器而被光谱仪接收。
进入PDMS腔F-P干涉计的入射光在界面M1处，一部分光反射回单模光纤，另一部分光透射进入PDMS腔，然后一部分光被界面M2反射回单模光纤。
Sagnac环和PDMS腔的干涉谱可表示为
Figure PCTCN2022082610-appb-000009
其中，λ为入射光波长，I 1(λ)表示Sagnac环的干涉谱强度，I 2(λ)表示PDMS腔F-P干涉计的干涉谱强度。A 1表示Sagnac环的干涉谱振幅，A 2表示PDMS腔F-P干涉计的干涉谱振幅。n为PDMS的折射率，其值约为1.40，B是双折射系数，其值为3×10 -4。Sagnac环和PDMS腔F-P干涉计构成并联结构，光谱仪接收到的光谱为Sagnac环和PDMS腔F-P干涉计的叠加。当Sagnac 环的自由光谱范围FSR1与PDMS腔F-P干涉计的自由光谱范围FSR2接近但不相等时，并联双腔的干涉谱就会产生包络。
图4A是示出Sagnac干涉计的干涉谱和F-P干涉计的干涉谱的示意图。其中，纵坐标是光强，横坐标表示波长，FSI表示Sagnac干涉计，FPI表示F-P干涉计。
上文所述的包络参见图4B。
如图4B所示，该包络可表示为
Figure PCTCN2022082610-appb-000010
其中，I envelope(λ)表示上述干涉谱包络的谱强度；E为干涉谱包络振幅，M为常规游标效应的放大因子。
当温度变化时，Sagnac环内偏振光纤的双折射系数发生变化，因此，Sagnac环的温度灵敏度S 1可表示为
Figure PCTCN2022082610-appb-000011
其中，ΔB为温度升高1℃时偏振光纤折射率的变化量，ΔB<0。
Figure PCTCN2022082610-appb-000012
表示干涉谱峰值波长随温度的变化率。
当温度变化时，PDMS腔的腔长和折射率均发生变化，因此，PDMS腔的温度灵敏度S 2可表示为
Figure PCTCN2022082610-appb-000013
其中，α表示PDMS的热光系数，λ m表示干涉谱峰值波长。β为PDMS的热膨胀系数，其值约为9.6×10 -4/℃。
由公式(3)和公式(4)可知，S 1<0，S 2>0为正值，即温度变化时，Sagnac环和PDMS腔干涉谱的频移方向相反。当Sagnac环和PDMS腔的自由光谱 范围相近但不相等时，并联后干涉谱就会产生包络，干涉谱包络随温度的平移量将远大于单个Sagnac环和单个PDMS腔，其灵敏度S 12为
Figure PCTCN2022082610-appb-000014
Figure PCTCN2022082610-appb-000015
由公式(5)和(6)可知，本实施例提出的温度传感器实现了增强型游标效应，温度灵敏度比单个Sagnac环和单个PDMS腔的灵敏度分别提高了M 1′和M 2′，放大倍率M 1′和M 2′都明显大于常规游标效应放大倍率M。
与现有技术专利申请201810971799.7相比，相同、区别和优点：(1)相同点：均利用了游标效应技术提高传感器灵敏度；不同点1：具体结构不同，201810971799.7为双腔串联结构，本实施例为Sagnac环和PDMS腔的并联结构；现有技术201810971799.7未用PDMS材料增敏，本实施例使用了PDMS增敏；现有技术201810971799.7中的两个F-P腔，其中一个为传感器，另一个为参考腔，而本实施例中的Saganc环和PDMS腔均为传感器，构成的游标效应为增强型，在相同结构参数条件下，本专利的灵敏度放大倍率远高于以上专利。
此外，与现有技术专利申请201810738431.6相比，区别和优点：201810738431.6采用了镀膜和胶粘的方式制作光纤微腔，制备过程复杂，镀膜需要昂贵的镀膜设备，而且耗时较长，胶粘方式使得传感器稳定性变差；本专利采用光纤熔接方式制备光纤微腔，操作简单，不需要昂贵设备。
综上所述，本实施例具有如下优点：1)仅采用光纤熔接制备方法，制作简单，不需要昂贵的专用设备；2)不需要胶粘，传感器稳定性好；3)双腔并联可产生游标效应，提高灵敏度，而且干涉谱包络消光比可调；4)产生增强型游标效应，灵敏度放大倍率更高。
应当注意，尽管在上文详细描述中提及了上述***的若干单元、模块或 子模块，但是这种划分仅仅是示例性的并非强制性的。实际上，根据本发明的实施方式，上文描述的两个或更多模块的特征和功能可以在一个模块中具体化。反之，上文描述的一个模块的特征和功能可以进一步划分为由多个模块来具体化。
此外，尽管在附图中以特定顺序描述了本发明方法的操作，但是，这并非要求或者暗示必须按照该特定顺序来执行这些操作，或是必须执行全部所示的操作才能实现期望的结果。附加地或备选地，可以省略某些步骤，将多个步骤合并为一个步骤执行，和/或将一个步骤分解为多个步骤执行。
虽然已经参考若干具体实施方式描述了本发明的精神和原理，但是应该理解，本发明并不限于所公开的具体实施方式，对各方面的划分也不意味着这些方面中的特征不能组合以进行受益，这种划分仅是为了表述的方便。本发明旨在涵盖所附权利要求的精神和范围内所包括的各种修改和等同布置。

Claims (2)

  1. 一种光纤温度传感器，其特征在于，所述光纤温度传感器包括宽谱光源、第一光纤耦合器、光谱仪、第一传感干涉计以及第二传感干涉计；其中，所述第一传感干涉计与所述第二传感干涉计具有相反的温度响应；
    所述第一传感干涉计对应的第一自由光谱范围与所述第二传感干涉计对应的第二自由光谱范围接近但不相等；
    所述第一传感干涉计采用由第二光纤耦合器和偏振光纤构成的Sagnac干涉计，所述第二传感干涉计采用由单模光纤和PDMS腔连接而成的F-P干涉计，所述光纤温度传感器的温度灵敏度S 12如下：
    Figure PCTCN2022082610-appb-100001
    其中，
    Figure PCTCN2022082610-appb-100002
    M为常规游标效应的放大因子；
    S 1表示Sagnac干涉计的温度灵敏度，其中，
    Figure PCTCN2022082610-appb-100003
    B表示双折射系数，ΔB表示温度升高1℃时偏振光纤折射率的变化量，ΔB<0；
    S 2表示F-P干涉计的温度灵敏度，其中，
    Figure PCTCN2022082610-appb-100004
    α表示PDMS的热光系数，λ m表示干涉谱峰值波长，n表示PDMS的折射率，β为PDMS的热膨胀系数；
    所述光纤温度传感器还包括光纤隔离器和衰减器；
    所述宽谱光源输出的入射光依次经所述光纤隔离器和所述第一光纤耦合器后分为两路，其中一路进入所述Sagnac干涉计，另一路经所述衰减器 进入所述F-P干涉计，通过所述光谱仪获得由所述Sagnac干涉计返回的干涉谱与由所述F-P干涉计返回的干涉谱的叠加结果；
    所述第二光纤耦合器的第一端连接至所述第一光纤耦合器，所述偏振光纤连接于所述第二光纤耦合器的第二端和第三端之间，进入所述Sagnac干涉计的入射光在所述偏振光纤内分为偏振方向相互垂直的两束光束，经所述偏振光纤后两光束之间发生干涉，得到的干涉光从所述第二光纤耦合器的第一端输出后再经所述第一光纤耦合器而被光谱仪接收；
    进入所述F-P干涉计的入射光的一部分光被所述单模光纤与所述PDMS腔的界面处反射回所述单模光纤，另一部分光透射进入所述PDMS腔后被所述PDMS腔与空气的界面处部分反射回所述单模光纤后，与被所述单模光纤与所述PDMS腔的界面处反射回所述单模光纤的所述一部分光干涉；
    其中，所述偏振光纤的长度与所述PDMS腔的轴向长度被设置成：使得所述Sagnac干涉计的第一自由光谱范围与所述F-P干涉计的第二自由光谱范围接近但不相等。
  2. 根据权利要求1所述的光纤温度传感器，其特征在于，第一自由光谱范围与第二自由光谱范围接近但不相等包括：
    第一自由光谱范围与第二自由光谱范围之间的差异部分占第一自由光谱范围与第二自由光谱范围的并集之比大于第一预设值、且小于第二预设值。
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