CN114166372A - Optical fiber temperature sensor based on PDMS filling and hybrid interferometer vernier sensitization - Google Patents

Optical fiber temperature sensor based on PDMS filling and hybrid interferometer vernier sensitization Download PDF

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CN114166372A
CN114166372A CN202111482755.6A CN202111482755A CN114166372A CN 114166372 A CN114166372 A CN 114166372A CN 202111482755 A CN202111482755 A CN 202111482755A CN 114166372 A CN114166372 A CN 114166372A
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optical fiber
pdms
interferometer
sensing head
vernier
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杨文龙
潘锐
李林军
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Harbin University of Science and Technology
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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

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Abstract

An optical fiber temperature sensor based on PDMS (polydimethylsiloxane) filling and hybrid interferometer vernier sensitization belongs to the technical field of optical fiber sensing. The invention solves the problems that the existing temperature sensor has low sensitivity and low integration level and can not measure tiny temperature change. The invention adopts the single mode fiber, the multimode fiber and the suspension core fiber to prepare the sensing head, improves the sensitivity of the sensor by filling PDMS, and improves the sensitivity again by the vernier effect generated by the series-parallel interferometer. The sensor of the invention realizes the improvement of one to two orders of magnitude of sensitivity by combining with PDMS, and improves the sensitivity by M times again through the vernier effect secondary sensitization, thereby obviously improving the sensitivity of temperature detection. The sensor has the advantages of high integration level, high sensitivity, stable structure and simple preparation, and can be applied to the field of high-precision temperature detection.

Description

Optical fiber temperature sensor based on PDMS filling and hybrid interferometer vernier sensitization
Technical Field
The invention belongs to the technical field of optical fiber sensing, and particularly relates to an optical fiber temperature sensor based on PDMS (polydimethylsiloxane) filling and vernier sensitization of a series-parallel interferometer.
Background
Accurate measurement of temperature changes is of great importance to the fields of environmental monitoring, biomedical and industrial production. The optical fiber temperature sensor has the advantages of good stability, electromagnetic interference resistance, small transmission loss and the like, and can realize the advantages of long-distance and extreme environment measurement, and the optical fiber temperature sensor has attracted much attention in the field of sensors in recent years.
However, the sensitivity of the existing optical fiber temperature sensor cannot meet the requirements of some high-precision temperature detection fields. Therefore, it is necessary to design an optical fiber temperature sensor to realize high-sensitivity temperature measurement.
Disclosure of Invention
In order to solve the problem of low sensitivity of the existing optical fiber temperature sensor, the invention provides an optical fiber temperature sensor based on PDMS filling and vernier sensitization of a series-parallel interferometer. The sensor of the invention realizes the improvement of one to two orders of magnitude of sensitivity by combining with PDMS, and improves the sensitivity by M times again through the vernier effect secondary sensitization, thereby obviously improving the sensitivity of temperature detection. The sensor has the advantages of high integration level, high sensitivity, stable structure and simple preparation, and can be applied to the field of high-precision temperature detection.
The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides an optic fibre temperature sensor based on PDMS fills and series-parallel interferometer vernier sensitization which characterized in that: the device comprises a broadband light source, an optical fiber circulator, a sensing head and a spectrometer.
The broadband light source is connected with a port 1 of the optical fiber circulator to provide detection light; the sensing head is connected with the 2-port of the optical fiber circulator to measure the change of the ambient temperature; the spectrum analyzer is connected with the 3 ports of the optical fiber circulator and receives and displays the reflection spectrum of the sensing head.
The detection light is wide spectrum light, is emitted by a broadband light source, enters the optical fiber circulator through the port of the optical fiber circulator 1, enters the sensing head from the port of the optical fiber circulator 2, is reflected by the sensing head, returns to the optical fiber circulator through the port of the optical fiber circulator 2 again, enters the spectrum analyzer from the port of the optical fiber circulator 3, and is received and displayed by the spectrum analyzer.
The sensing head comprises a single-mode optical fiber, a multi-mode optical fiber and a suspension core optical fiber, wherein one end of the multi-mode optical fiber is welded with the single-mode optical fiber, the other end of the multi-mode optical fiber is welded with the suspension core optical fiber, and the air hole of the suspension core optical fiber is filled with PDMS; the fusion joint surface of the multimode optical fiber and the suspension core optical fiber is a reflecting surface I, and the contact surface of the suspension core optical fiber and air is a reflecting surface II.
Furthermore, the single-mode optical fiber has an outer diameter of 125 micrometers and an inner diameter of 8-9 micrometers; the multimode optical fiber has an outer diameter of 125 microns, an inner diameter of 60 microns and a length of 100-150 microns; the outer diameter of the suspension core optical fiber is 125 micrometers, the inner part of the suspension core optical fiber contains an air hole positioned at the central position and a fiber core internally tangent to the air hole, the diameter of the air hole is 40 micrometers, the diameter of the fiber core is 8-9 micrometers, and the length of the fiber core is 200-300 micrometers.
Further, the PDMS has a high thermal expansion coefficient (9.6 x 10)-4) And a high thermo-optic coefficient (-4.6 x 10)-4) The optical fiber is filled with internal air holes of the suspended core optical fiber, and the length of the optical fiber is the same as that of the suspended core optical fiber.
Furthermore, after entering the sensing head, the detection light sequentially passes through the single-mode fiber, the multimode fiber and the suspension core fiber and is reflected by the reflecting surface I and the reflecting surface II, the reflecting surface I generates the reflected light I, and the reflecting surface II generates the reflected light II and the reflected light III.
Further, the reflected light I and the reflected light II form a Fabry-Perot interferometer as a sensing interferometer; the reflected light I and the reflected light III form a Michelson interferometer as a reference interferometer; the two interferometers form a highly integrated parallel structure, so that the vernier effect sensitization is realized, and the sensitivity of environment temperature detection is improved by measuring the translation amount of the reflected spectrum envelope of the sensing head.
Further, the translation amount of the spectrum envelope of the reflection spectrum of the sensing head is as follows:
when the environmental temperature changes, the length and the refractive index of PDMS change due to the thermal expansion effect and the thermo-optic effect, so that the cavity length and the refractive index of a medium in the cavity of the Fabry-Perot interferometer change, the reflection spectrum of the Fabry-Perot interferometer moves, the reflection spectrum envelope of the sensing head moves along with the change, and the translation quantity delta lambda of the reflection spectrum envelope of the sensing head movesEnvelopeExpressed as:
ΔλEnvelope＝M·ΔλFPI＝M·λ(αL1+βnPDMS)
where M is the amplification factor of the envelope, Δ λFPIThe displacement of the reflection spectrum of the Fabry-Perot interferometer is measured, lambda is the incident wavelength of the probe light, alpha is the thermal expansion coefficient of PDMS, beta is the thermal optical coefficient of PDMS, and L1Is the cavity length, n, of a Fabry-Perot interferometerPDMSIs a fabry-refractive index of the medium (PDMS) inside the cavity of the perot interferometer.
The invention has the beneficial effects that:
the invention provides an optical fiber temperature sensor based on PDMS filling and vernier sensitization of a series-parallel interferometer. The invention adopts the single mode fiber, the multimode fiber and the suspension core fiber to prepare the sensing head, and fills the internal air holes of the suspension core fiber with PDMS, so that the PDMS and the suspension core fiber have the same length, thereby ensuring that the two interferometers have the same cavity length, realizing the vernier effect and needing the detuning amount only from the refractive index difference of substances in the cavities of the two interferometers, simplifying the preparation process and simultaneously removing the complex regulation and control process of the detuning amount of the two interferometers. The sensor of the invention realizes the improvement of one to two orders of magnitude of sensitivity by combining with PDMS, and improves the sensitivity by M times again through the vernier effect secondary sensitization, thereby obviously improving the sensitivity of temperature detection. The sensor has the advantages of high integration level, high sensitivity, stable structure and simple preparation, and can be applied to the field of high-precision temperature detection.
Drawings
FIG. 1 is a schematic structural diagram of an optical fiber temperature sensor based on PDMS filling and hybrid interferometer vernier sensitization according to the present invention;
FIG. 2 is a schematic diagram of a sensor head configuration;
FIG. 3 is a schematic diagram of a suspended core optical fiber configuration;
FIG. 4 is a graph of a sensor head reflection spectral envelope;
FIG. 5 is a variation of a reflection spectrum with ambient temperature, wherein (a) a Fabry-Perot interferometer; (b) a michelson interferometer; (c) a sensor head.
Detailed Description
For the purpose of clearly describing the embodiments of the present invention, the detailed description is made below with reference to the accompanying drawings.
The first embodiment is as follows: this embodiment a fiber temperature sensor based on PDMS fills and series-parallel interferometer vernier sensitization, its characterized in that: the device comprises a broadband light source, an optical fiber circulator, a sensing head and a spectrometer.
The broadband light source is connected with a port 1 of the optical fiber circulator to provide detection light; the sensing head is connected with the 2-port of the optical fiber circulator to measure the change of the ambient temperature; the spectrum analyzer is connected with the 3 port of the optical fiber circulator and receives and displays the reflection spectrum of the sensing head; the schematic diagram of the sensor structure is shown in fig. 1.
The detection light is wide spectrum light, is emitted by a broadband light source, enters the optical fiber circulator through the port of the optical fiber circulator 1, enters the sensing head from the port of the optical fiber circulator 2, is reflected by the sensing head, returns to the optical fiber circulator through the port of the optical fiber circulator 2 again, enters the spectrum analyzer from the port of the optical fiber circulator 3, and is received and displayed by the spectrum analyzer.
The sensing head comprises a single-mode optical fiber, a multimode optical fiber and a suspension core optical fiber, wherein one end of the multimode optical fiber is welded with the single-mode optical fiber, the other end of the multimode optical fiber is welded with the suspension core optical fiber, PDMS is filled in an air hole of the suspension core optical fiber, and the structural schematic diagram of the sensing head is shown in figure 2; the fusion joint surface of the multimode optical fiber and the suspension core optical fiber is a reflecting surface I, and the contact surface of the suspension core optical fiber and air is a reflecting surface II.
The single-mode optical fiber has an outer diameter of 125 micrometers and an inner diameter of 8-9 micrometers; the multimode optical fiber has an outer diameter of 125 microns, an inner diameter of 60 microns and a length of 100-150 microns; the outer diameter of the suspension core optical fiber is 125 micrometers, the inner part of the suspension core optical fiber contains an air hole positioned at the central position and a fiber core internally tangent to the air hole, the diameter of the air hole is 40 micrometers, the diameter of the fiber core is 8-9 micrometers, the length of the fiber core is 200-300 micrometers, and the structural schematic diagram of the suspension core optical fiber is shown in FIG. 3.
Said PDMS has a high thermal expansion coefficient (9.6 x 10)-4) And a high thermo-optic coefficient (-4.6 x 10)-4) The optical fiber is filled with internal air holes of the suspended core optical fiber, and the length of the optical fiber is the same as that of the suspended core optical fiber.
After entering the sensing head, the detection light sequentially passes through the single-mode optical fiber, the multi-mode optical fiber and the suspension core optical fiber and is reflected by the reflecting surface I and the reflecting surface II, the reflecting surface I generates reflected light I, and the reflecting surface II generates reflected light II and reflected light III; the reflected light I and the reflected light II form a Fabry-Perot interferometer as a sensing interferometer; the reflected light I and the reflected light III form a Michelson interferometer as a reference interferometer; the two interferometers form a highly integrated parallel structure, so that the vernier effect sensitization is realized, and the sensitivity of environment temperature detection is improved by measuring the translation amount of the reflected spectrum envelope of the sensing head.
The reflection spectrum function of the two interferometers can be expressed as follows:
IFPI＝A2+B2+2ABcos(4πnPDMSL1/λ)
IMI＝A2+C2+2ACcos(4πnSMFL2/λ)
wherein A ═ R1 1/2；B＝(1-s1)(1-R1)R2 1/2；C＝(1-s2)(1-R1)R3 1/2；nPDMSAnd nSMFRefractive indexes of a Fabry-Perot interferometer intracavity medium (PDMS) and a Michelson interferometer intracavity medium (quartz) are respectively; l is1And L2The cavity lengths of a Fabry-Perot interferometer and a Michelson interferometer respectively; λ is the incident wavelength of the probe light; s1And s2The transmission loss of the detection light in the Fabry-Perot interferometer and the Michelson interferometer respectively; r1Is the reflection coefficient of the reflected light I at the reflecting surface I; r2，R3Respectively, the reflection coefficients of the reflected light II and the reflected light III at the reflection surface II.
The two interferometers are slightly detuned, so that under the double filtering action of the two interferometers, the reflection spectrum of the sensing head generates periodic vernier interference fringes, thereby generating a periodic envelope. The sensing head reflection spectrum envelope function can be expressed as:
Figure BDA0003395492820000041
where M is the amplification factor of the envelope, which typically ranges from 5 to 30, and can be expressed as:
Figure BDA0003395492820000042
the translational quantity of the reflection spectrum of the Fabry-Perot interferometer is as follows: when the environment temperature changes, the length and the refractive index of PDMS change due to the thermal expansion effect and the thermo-optic effect, so that the cavity length and the refractive index of a medium in the cavity of the Fabry-Perot interferometer change, the reflection spectrum of the Fabry-Perot interferometer moves, and the translation quantity delta lambda of the reflection spectrum of the Fabry-Perot interferometerFPICan be expressed as:
Figure BDA0003395492820000043
wherein, Δ L1Is the variation of the cavity length of the Fabry-Perot interferometer, DeltanPDMSThe variable quantity of the refractive index of a medium (PDMS) in a cavity of the Fabry-Perot interferometer is shown, wherein alpha is the thermal expansion coefficient of the PDMS, and beta is the thermal optical coefficient of the PDMS.
The translation amount of the reflected spectrum envelope of the sensing head is as follows: when the environmental temperature changes, the reflection spectrum of the Fabry-Perot interferometer moves, the reflection spectrum envelope of the sensing head moves along with the reflection spectrum envelope, and the translation quantity delta lambda of the reflection spectrum envelope of the sensing headEnvelopeExpressed as:
ΔλEnvelope＝M·ΔλFPI＝M·λ(αL1+βnPDMS)
the above formula shows that: when the environment temperature changes, the spectrum reflected by the Fabry-Perot interferometer moves along with the change of the environment temperature due to the thermal expansion effect and the thermo-optic effect of the PDMS, the spectrum envelope reflected by the sensing head moves along with the change of the environment temperature, and the translation amount is M times of the translation amount of the spectrum reflected by the Fabry-Perot interferometer.
The embodiments of the present invention are provided only for facilitating understanding of the technical solutions of the present invention, and do not limit the present invention. Workers skilled in the art will recognize that changes may be made in form and detail without departing from the general concept defined by the claims and their equivalents.

Claims (6)

1. The utility model provides an optic fibre temperature sensor based on PDMS (polydimethylsiloxane) fills and series-parallel interferometer vernier sensitization which characterized in that: the device comprises a broadband light source, an optical fiber circulator, a sensing head and a spectrometer;
the broadband light source is connected with a port 1 of the optical fiber circulator to provide detection light; the sensing head is connected with the 2-port of the optical fiber circulator to measure the change of the ambient temperature; the spectrum analyzer is connected with the 3 port of the optical fiber circulator and receives and displays the reflection spectrum of the sensing head;
the detection light is wide spectrum light, is emitted by a broadband light source, enters the optical fiber circulator through a port of the optical fiber circulator 1, enters the sensing head from a port of the optical fiber circulator 2, is reflected by the sensing head, returns to the optical fiber circulator through a port of the optical fiber circulator 2 again, enters the optical spectrum analyzer from a port of the optical fiber circulator 3, and is received and displayed by the optical spectrum analyzer;
the sensing head comprises a single-mode optical fiber, a multi-mode optical fiber and a suspension core optical fiber, wherein one end of the multi-mode optical fiber is welded with the single-mode optical fiber, the other end of the multi-mode optical fiber is welded with the suspension core optical fiber, and the air hole of the suspension core optical fiber is filled with PDMS; the fusion joint surface of the multimode optical fiber and the suspension core optical fiber is a reflecting surface I, and the contact surface of the suspension core optical fiber and air is a reflecting surface II.
2. The PDMS-filled and hybrid interferometer vernier-based fiber optic temperature sensor of claim 1, wherein: the single-mode optical fiber has an outer diameter of 125 micrometers and an inner diameter of 8-9 micrometers; the multimode optical fiber has an outer diameter of 125 microns, an inner diameter of 60 microns and a length of 100-150 microns; the outer diameter of the suspension core optical fiber is 125 micrometers, the inner part of the suspension core optical fiber contains an air hole positioned at the central position and a fiber core internally tangent to the air hole, the diameter of the air hole is 40 micrometers, the diameter of the fiber core is 8-9 micrometers, and the length of the fiber core is 200-300 micrometers.
3. The PDMS-filled and hybrid interferometer vernier-based fiber optic temperature sensor of claim 1, wherein: said PDMS has a high thermal expansion coefficient (9.6 x 10)-4) And a high thermo-optic coefficient (-4.6 x 10)-4) Filled with suspended core optical fibresThe length of the internal air hole is the same as that of the suspended core optical fiber.
4. The PDMS-filled and hybrid interferometer vernier-based fiber optic temperature sensor of claim 1, wherein: after entering the sensing head, the detection light sequentially passes through the single-mode optical fiber, the multi-mode optical fiber and the suspension core optical fiber and is reflected by the reflecting surface I and the reflecting surface II, the reflecting surface I generates reflected light I, and the reflecting surface II generates reflected light II and reflected light III.
5. The PDMS-filled and hybrid interferometer vernier-based fiber optic temperature sensor of claim 4, wherein: the reflected light I and the reflected light II form a Fabry-Perot interferometer as a sensing interferometer; the reflected light I and the reflected light III form a Michelson interferometer as a reference interferometer; the two interferometers form a highly integrated parallel structure, so that the vernier effect sensitization is realized, and the sensitivity of environment temperature detection is improved by measuring the translation amount of the reflected spectrum envelope of the sensing head.
6. The PDMS-filled and hybrid interferometer vernier-based fiber optic temperature sensor of claim 5, wherein:
the translation amount of the reflected spectrum envelope of the sensing head is as follows:
when the environmental temperature changes, the length and the refractive index of PDMS change due to the thermal expansion effect and the thermo-optic effect, so that the cavity length and the refractive index of a medium in the cavity of the Fabry-Perot interferometer change, the reflection spectrum of the Fabry-Perot interferometer moves, the reflection spectrum envelope of the sensing head moves along with the change, and the translation quantity delta lambda of the reflection spectrum envelope of the sensing head movesEnvelopeExpressed as:
ΔλEnvelope＝M·ΔλFPI＝M·λ(αL1+βnPDMS)
where M is the amplification factor of the envelope, Δ λFPIThe displacement of the reflection spectrum of the Fabry-Perot interferometer is measured, lambda is the incident wavelength of the probe light, alpha is the thermal expansion coefficient of PDMS, and beta is the thermal optical system of PDMSNumber, L1Is the cavity length, n, of a Fabry-Perot interferometerPDMSIs the refractive index of the Fabry-Perot interferometer intracavity medium (PDMS).
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116608891A (en) * 2023-07-20 2023-08-18 山东省科学院激光研究所 Optical fiber F-P cavity sensor and manufacturing method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116608891A (en) * 2023-07-20 2023-08-18 山东省科学院激光研究所 Optical fiber F-P cavity sensor and manufacturing method thereof
CN116608891B (en) * 2023-07-20 2023-11-03 山东省科学院激光研究所 Optical fiber F-P cavity sensor and manufacturing method thereof

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