CN115235517A - Fiber grating double-parameter sensor and device based on combined special optical fiber - Google Patents

Fiber grating double-parameter sensor and device based on combined special optical fiber Download PDF

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CN115235517A
CN115235517A CN202210791377.8A CN202210791377A CN115235517A CN 115235517 A CN115235517 A CN 115235517A CN 202210791377 A CN202210791377 A CN 202210791377A CN 115235517 A CN115235517 A CN 115235517A
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fiber
optical fiber
grating
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photosensitive
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凌强
王鑫玉
陈达如
郁张维
陈海云
管祖光
邵杰
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Zhejiang Normal University CJNU
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    • 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
    • G01D5/35374—Particular layout of the fiber
    • 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
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • 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
    • G01D5/3538—Optical fibre sensor using a particular arrangement of the optical fibre itself using a particular type of fiber, e.g. fibre with several cores, PANDA fiber, fiber with an elliptic core or the like
    • 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
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • 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
    • G02B6/255—Splicing of light guides, e.g. by fusion or bonding
    • G02B6/2551—Splicing of light guides, e.g. by fusion or bonding using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
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Abstract

The invention discloses a fiber grating double-parameter sensor and a device based on a combined special optical fiber. The fiber bragg grating dual-parameter sensor comprises a plurality of sections of seven-core optical fibers and photosensitive optical fibers, wherein the photosensitive optical fibers are welded between adjacent seven-core optical fiber sections, and a certain section of photosensitive optical fiber positioned between the adjacent seven-core optical fiber sections is processed into a fiber bragg grating. The output port of a broadband light source in the sensing device is connected with one end of a first section of single-mode optical fiber; the other end of the first section of single-mode fiber is connected with one end of the fiber grating double-parameter sensor; the other end of the fiber bragg grating double-parameter sensor is connected with one end of the second section of single-mode fiber; the other end of the second section of single-mode fiber is connected with the input port of the spectrometer. The combined fiber grating spectrum of the invention presents two resonance peaks, and the measurement of bending and temperature can be realized simultaneously by the demodulation of the two resonance peaks.

Description

Fiber grating double-parameter sensor and device based on combined special optical fiber
Technical Field
The invention relates to the technical field of fiber grating sensing, in particular to a device for realizing simultaneous measurement of bending and temperature of a fiber grating double-parameter sensor based on a combined special fiber.
Background
The optical fiber sensor is widely applied to various environmental parameter detection with the advantages of small volume, high sensitivity, simple structure, electromagnetic interference resistance and the like, such as: temperature, strain, bend, twist, and ambient refractive index, among others. The optical fiber bending sensor has important significance in the fields of aerospace, machinery, building structure health detection and the like. Under a complex actual measurement environment, measurement requirements cannot be met by measurement of a single bending change, for example, cross sensitivity problems caused by environmental temperature changes limit application of the sensor, and therefore, an optical fiber sensing device capable of realizing bending and temperature measurement needs to be designed and manufactured.
The fiber grating sensor is one of the most mature types of fiber sensors, and compared with an interference type fiber sensor, the fiber grating sensor has the advantages of high sensitivity, diversified structure, high stability and the like. At present, the application of the fiber grating sensor is limited mainly in two aspects, on one hand, the manufacturing means of the fiber grating, such as common grating manufacturing means, ultraviolet exposure method, femtosecond laser etching method and CO 2 The laser point-by-point writing method and the like have the problem of high manufacturing equipment price; on the other hand, the problem of cross-connection between different environmental parameters, particularly the interference caused by temperature in the bending measurement process, is solved.
Disclosure of Invention
In order to solve the technical problems and provide a sensing method which is low in manufacturing cost and compact in structure and can realize simultaneous measurement of bending and temperature, the invention provides a fiber bragg grating dual-parameter sensor and a sensing device based on a combined special optical fiber so as to realize simultaneous measurement of bending and temperature.
The invention provides a fiber grating dual-parameter sensor based on a combined special optical fiber, which comprises a plurality of sections of seven-core optical fibers and photosensitive optical fibers, wherein the photosensitive optical fibers are welded between adjacent seven-core optical fiber sections, and a certain section of photosensitive optical fiber positioned between the adjacent seven-core optical fiber sections is processed into a fiber Bragg grating.
Another aspect of the present invention provides a method for manufacturing the fiber grating dual-parameter sensor, including the following steps:
welding the single-mode optical fiber and the seven-core optical fiber with flat end faces by using a welding machine;
cutting the seven-core optical fiber by using a cutting knife under the observation of a microscopic observation system;
welding the other end of the seven-core optical fiber and the photosensitive optical fiber by using a welding machine;
under the observation of a microscopic observation system, cutting the photosensitive fiber by using a cutting knife, so as to obtain a long-period fiber grating with a single period;
repeating the steps for n times to obtain the long-period fiber grating with the period number of n;
and (3) outputting ultraviolet light by using a deep ultraviolet laser, and irradiating any section of photosensitive optical fiber through a phase mask plate to form the fiber Bragg grating.
The invention also provides a fiber grating double-parameter sensing device, which comprises a broadband light source, a spectrometer and a fiber grating double-parameter sensor;
the output port of the broadband light source is connected with one end of the first section of single-mode fiber; the other end of the first section of single-mode fiber is connected with one end of the fiber grating double-parameter sensor; the other end of the fiber bragg grating double-parameter sensor is connected with one end of the second section of single-mode fiber; the other end of the second section of single-mode fiber is connected with the input port of the single-mode fiber of the spectrometer.
Bending and temperature variation are obtained through variation of central wavelengths of two resonance peaks monitored by a spectrometer, one of the variation of the central wavelengths of the two resonance peaks is from a long-period fiber grating, the other one of the variation of the central wavelengths of the two resonance peaks is from a fiber Bragg grating, and the long-period fiber grating consists of a section of seven-core optical fiber and a section of photosensitive optical fiber.
The spectrum of the combined fiber grating manufactured by the invention presents two resonance peaks, the measurement of bending and temperature can be realized simultaneously by the demodulation of the two resonance peaks, and the combined fiber grating has the advantages of electromagnetic interference resistance, compact structure, high sensitivity, low price and the like because the combined fiber grating is used as a sensing medium.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic view of a combined fiber grating structure;
FIG. 3 is a schematic diagram of a process for fabricating a combined fiber grating;
FIG. 4 is a spectrum experimental diagram of the combined fiber grating;
FIG. 5 is a diagram of a combined fiber grating bend and temperature measurement apparatus.
Detailed Description
As shown in fig. 1, the device for simultaneously measuring bending and temperature by using a fiber grating based on a combined special optical fiber according to the present invention includes a broadband light source 1, a single-mode fiber 2, a combined fiber grating 3, a second single-mode fiber 4 and a spectrometer 5. A broadband light source 1 covering a wave band 1510nm-1630nm guides light beams into a combined fiber grating 3 through a single mode fiber 2, and the light beams are modulated by the combined fiber grating and then output to a spectrometer 5 through a single mode fiber 4 to monitor spectra.
The basic structure of the combined fiber grating is shown in fig. 2, and basically comprises a long-period fiber grating section 9 consisting of a seven-core fiber section 6 and a photosensitive fiber section 7, and a fiber bragg grating 8 made of a photosensitive fiber. The combined fiber grating sensor is a long-period fiber grating and fiber Bragg grating overlapped fiber grating structure manufactured by adopting different manufacturing methods. Wherein the long-period fiber grating is made by cutting and welding the seven-core fiber and the photosensitive fiber at micron scale by using a welding machine, a cutter and a microscopic observation system; the length of each section of seven-core optical fiber is 225 μm, and the length of the photosensitive optical fiber is 400 μm. The fiber Bragg grating is manufactured by performing ultraviolet light exposure on any section of photosensitive fiber by a phase mask method, and the central wavelength of the fiber Bragg grating is 1535nm.
Fig. 3 shows a specific manufacturing method of the combined fiber grating, which comprises the following steps: firstly, a welding machine 11 is used for welding the single-mode optical fiber 2 and the seven-core optical fiber 6 with smooth end faces; under the observation of a microscopic observation system 12, cutting the seven-core optical fiber 6 by using a cutting knife 13 to obtain the seven-core optical fiber with the length of 225 mu m; welding the other end of the seven-core optical fiber to the photosensitive optical fiber 7 by using the welding machine 11 again; under the observation of a microscopic observation system 12, cutting the photosensitive fiber 7 by using a cutting knife 13, so as to obtain a long-period fiber grating with a single period; repeating the above steps (i.e. fig. 3 (a), (b) and (c)) 9 times to obtain the long-period fiber grating 9 with the period number of 9; and (3) outputting ultraviolet light by using a deep ultraviolet laser 14 with the output wavelength of 213nm to irradiate the photosensitive fiber through a phase mask plate 15 to form a fiber Bragg grating 8, so as to obtain the combined fiber grating 3.
When broadband light enters the combined fiber bragg grating through the single-mode fiber, under the combined influence of the long-period fiber bragg grating and the fiber bragg grating in the overlapped structure, part of the fiber core module energy transmitted in the forward direction is coupled to the cladding module transmitted in the forward direction, part of the fiber core module energy transmitted in the backward direction is coupled, and the rest part of the energy is still transmitted in the fiber core in the forward direction. Under the influence of the long-period fiber grating, the coupling between the fiber core mode and the forward cladding mode of forward transmission enables the spectrometer to present a loss peak, and the wavelength corresponding to the peak value of the loss peak is
Figure BDA0003730404600000041
Wherein,
Figure BDA0003730404600000042
is the effective refractive index difference between the core mode and the cladding mode, Λ LPFG Being the period of a long-period fibre grating, i.e. Λ LPFG =625 μm. Due to the fact that
Figure BDA0003730404600000043
And Λ LPFG Are both a function of bending curvature and temperature, and thus cause a resonant wavelength λ when bending and temperature changes LPFG Of (3) is detected.
Under the influence of the fiber Bragg grating, the direct coupling of the forward transmission fiber core mode and the backward transmission cladding mode ensures that the spectrometer also presents a loss peak, and the wavelength corresponding to the loss peak is
Figure BDA0003730404600000044
Wherein,
Figure BDA0003730404600000045
is the effective refractive index difference of the fiber core model, lambda FBG The period of the long-period fiber grating. Due to the fact that
Figure BDA0003730404600000046
And Λ FBG Are both a function of bending curvature and temperature, and thus cause a resonant wavelength λ when bending and temperature changes FBG Of (3) is detected.
In the implementation process, the parameters of the selected long-period fiber grating are as follows: the grating period is 625 μm, the length of the seven-core fiber in each period is 225 μm, and the length of the photosensitive fiber is 400 μm. The selected fiber bragg grating center wavelength was 1535nm. During the manufacturing process, the spectrometer shown in fig. 1 is used to record the spectrum variation, and after the manufacturing process is completed, the output spectrum is shown in fig. 4. The combined fiber grating is formed by overlapping and combining a long-period fiber grating and a fiber Bragg grating, two resonance peaks are presented in a spectrum, and the central wavelengths are respectively lambda LPFG And λ FBG . Through bending and temperature sensing experiments, a sensitivity coefficient matrix of the combined fiber grating is established from the research of a bay area of two resonance peaks and temperature innovation characteristics, so that the bending and temperature can be measured simultaneously.
FIG. 5 shows a combined fiber grating bendGraph of curve and temperature measurement device. Output light of the broadband light source 1 enters the combined fiber grating 3 through the single-mode fiber 2 and is output to the spectrometer 5 through the single-mode fiber 4. The spectrometer monitors the spectrum condition of the combined fiber bragg grating sensing under different parameters. In the bending measurement process, one end of the combined fiber grating is fixed by the fiber fixing clamp 16, the other end of the combined fiber grating is fixed by the fiber fixing clamp 16 on the one-dimensional micro-displacement platform 17, and the temperature is controlled to be constant by the constant temperature box 18 in the whole measurement process. The combined fiber grating is naturally bent by moving the position of the micro displacement platform 16, and different bending conditions are presented. In the temperature sensing process, the bending state of the combined fiber bragg grating is fixed, and the temperature control box 18 is controlled to change the ambient temperature. Determination of the resonance peak λ by bending and temperature sensing LPFG And λ FBG The sensitivity coefficients to bending and temperature are respectively K C,LPFG 、K C,FBG 、K T,LPFG 、K T,FBG . And constructing a sensitivity coefficient matrix according to the four measured coefficients:
Figure BDA0003730404600000051
wherein, Δ λ LPFG And Δ λ FBG Respectively, the shift in the center wavelength of the two resonance peaks, and deltac and deltat are the known amounts of bend and temperature change, respectively.
When the combined fiber bragg grating sensor is used for measuring unknown bending and temperature change, the central wavelength variation delta lambda of two resonance peaks can be monitored by a spectrometer LPFG And Δ λ FBG The bending and temperature variation were obtained as:
Figure BDA0003730404600000052
wherein D = K C,LPFG K T,FBG -K C,FBG K T,LPFG 。
The invention provides a technical scheme for optical fiber bending and temperature sensing by utilizing the newly-proposed welding combination technology for manufacturing a long-period optical fiber grating, the ultraviolet exposure method technology for manufacturing an optical fiber Bragg grating by exposing a photosensitive optical fiber and the dual-wavelength matrix method and utilizing the sensing characteristics of the long-period optical fiber grating and the optical fiber Bragg grating on bending and temperature sensitivity. The invention adopts the fiber grating of the combined special fiber as a sensing component, and has the advantages of electromagnetic interference resistance, compact structure, high sensitivity, low price and the like.

Claims (4)

1. Fiber grating double-parameter sensor based on combined special optical fiber, its characterized in that: the optical fiber Bragg grating comprises a plurality of sections of seven-core optical fibers and photosensitive optical fibers, wherein the photosensitive optical fibers are welded between adjacent seven-core optical fiber sections, and a certain section of photosensitive optical fiber positioned between the adjacent seven-core optical fiber sections is processed into the optical fiber Bragg grating.
2. A method for manufacturing a fiber grating bi-parametric sensor according to claim 1, wherein:
welding the single-mode optical fiber and the seven-core optical fiber with flat end faces by using a welding machine;
cutting the seven-core optical fiber by using a cutting knife under the observation of a microscopic observation system;
welding the other end of the seven-core optical fiber and the photosensitive optical fiber by using a welding machine;
under the observation of a microscopic observation system, cutting the photosensitive fiber by using a cutting knife so as to obtain a long-period fiber grating with a single period;
repeating the steps for n times to obtain the long-period fiber grating with the period number of n;
and (3) outputting ultraviolet light by using a deep ultraviolet laser, and irradiating any section of photosensitive optical fiber through a phase mask plate to form the fiber Bragg grating.
3. A fiber grating double-parameter sensing device comprises a broadband light source, a spectrometer and the fiber grating double-parameter sensor of claim 1, and is characterized in that:
the output port of the broadband light source is connected with one end of the first section of single-mode fiber; the other end of the first section of single-mode fiber is connected with one end of the fiber grating double-parameter sensor; the other end of the fiber bragg grating double-parameter sensor is connected with one end of the second section of single-mode fiber; the other end of the second section of single-mode fiber is connected with a single-mode fiber input port of the spectrometer;
bending and temperature variation are obtained through variation of central wavelengths of two resonance peaks monitored by a spectrometer, one of the variation of the central wavelengths of the two resonance peaks is from a long-period fiber grating, the other one of the variation of the central wavelengths of the two resonance peaks is from a fiber Bragg grating, and the long-period fiber grating consists of a section of seven-core optical fiber and a section of photosensitive optical fiber.
4. A fiber grating dual parametric sensor device according to claim 3, wherein: the length of each section of seven-core optical fiber is 225 μm, and the length of the photosensitive optical fiber is 400 μm.
CN202210791377.8A 2022-07-05 2022-07-05 Fiber grating double-parameter sensor and device based on combined special optical fiber Pending CN115235517A (en)

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