Multi-parameter sensing device and sensing method based on multi-resonant fiber grating

Abstract

The invention discloses a multi-parameter sensing device and sensing method based on a multi-resonant fiber bragg grating, and the method comprises the steps: firstly, collecting the spectral response of parameters, which cause the drift of multi-resonant wavelengths, such as strain, temperature, refractive index, pressure and the like through experiments, and obtaining the multi-resonant wavelengths at different positions; secondly, obtaining the parameter sensitivity of different resonant wavelengths through the fitting slope of the extracted multi-resonant wavelength and the applied parameter, and dividing the parameter sensitivity of the resonant wavelength by the corresponding resonant wavelength when the parameter is not applied to calculate the parameter sensitivity coefficient of the corresponding resonant wavelength; thirdly, selecting the same and proper number of sensitivity coefficients of resonant wavelengths at different positions, and establishing a sensitivity coefficient matrix; and finally, multi-resonant wavelength drift of the multi-resonant fiber bragg grating is monitored, changes of parameters such as strain, temperature, refractive index and pressure are reversely deduced, simultaneous sensing of three or more parameters based on the multi-resonant fiber bragg grating is realized, and the multi-resonant fiber bragg grating sensor has the advantages of simple and compact structure, stability, firmness and the like.

Description

Technical Field

[0001] The invention proposes a multi-parameter sensing device and a sensing method based on a multi-resonance optical fiber grating, belonging to the technical field of multi-parameter optical fiber sensing. Background Art

[0002] Fiber optic biomedical and electrochemical sensors are one of the current research hotspots in the field of fiber optic sensing. Their sensing principles are generally based on fiber optic refractive index sensors or light absorption sensors. Such biomedical and chemical sensors have high requirements for measurement accuracy or detection limits, but the background noise of their sensing environment fluctuates greatly and is susceptible to crosstalk from strain and temperature changes. In addition, in order to improve sensing sensitivity and specificity, fiber optic biomedical and chemical sensors usually require additional functional material coatings, which creates potential problems such as stability and repeatability.

[0003] The number of solutions for two-parameter sensing is significantly greater than that for three or more parameters. Among two-parameter sensors, sensors for simultaneous sensing of refractive index and temperature have a larger number of reports on working principles and sensing methods. There are limited reports on three-parameter sensors, and it is clear that combining more than two parameters represents a major challenge. For fiber optic sensors, the sensing measurements for axial strain and temperature have been the most intensively and extensively studied, and their applications are also the earliest.

[0004] The multi-resonance fiber sensing structure can not only realize the simultaneous measurement or differentiation of multiple parameters by utilizing the different parameter sensitivities between resonances, but also provide multiple independent measurements for the same parameter sensing to reduce errors. Among them, compared with the fiber interferometer structure, the multi-resonance fiber grating (such as tilted fiber Bragg grating and eccentric fiber Bragg grating) has the advantages of high Q value resonance spectrum, exponential sensitivity difference resonance, and no crosstalk in the resonance mode. It is an ideal sensing structure for realizing high-precision in-situ monitoring of multiple parameters such as temperature, axial strain, refractive index, pressure, and bending curvature. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a multi-parameter sensing device and sensing method based on multi-resonance fiber Bragg grating, which realizes the simultaneous sensing of more than three parameters based on multi-resonance fiber Bragg grating. By accurately calibrating the multi-resonance axial strain, temperature, refractive index, pressure, humidity, bending sensitivity and sensitivity coefficient of the multi-resonance fiber Bragg grating, a sensitivity coefficient matrix related to the multi-resonance wavelength is established, the multi-resonance wavelength drift of the multi-resonance fiber Bragg grating is monitored, and the changes of multiple parameters such as axial strain, temperature, refractive index, pressure, bending, etc. are inferred at the same time, so as to simultaneously monitor and sense three or more external parameters.

[0006] The problem solved by the present invention is to provide a multi-parameter sensing device and a sensing method of a multi-resonance fiber grating, which can effectively realize simultaneous monitoring of three or more parameters based on the multi-resonance fiber grating according to the multi-resonance offset of the multi-resonance fiber grating.

[0007] The multi-parameter sensing device based on multi-resonance fiber Bragg grating of the present invention comprises a broadband light source, a polarization controller, a first single-mode fiber, a second single-mode fiber, a third single-mode fiber, a support rod, a horizontal displacement stage, a vertical displacement stage, a glass slide, a first two-dimensional fiber clamp, a second two-dimensional fiber clamp, a detachable dropper, a constant temperature and humidity chamber and a spectrum analyzer; the left end of the polarization controller is connected to the broadband light source, the right end of the polarization controller is connected to the left end of the first single-mode fiber, the right end of the first single-mode fiber is connected to the left end of the third single-mode fiber, the left end of the second single-mode fiber is connected to the right end of the third single-mode fiber, and the right end of the second single-mode fiber is connected to the spectrum analyzer; wherein the core of the third single-mode fiber is engraved with the tilted fiber Bragg grating, the polarization controller is used to control the polarization state of the incident light, and the polarization controller is adjusted so that the light output is respectively in S and P polarization states, and the detachable dropper is located at the top of the constant temperature and humidity chamber and directly faces the glass slide.

[0008] Furthermore, the broadband light source operates in the near-infrared band and is a continuous light source with a scanning range of 1515nm-1615nm.

[0009] Furthermore, the fiber fusion splicer model used for connecting the first single-mode optical fiber, the second single-mode optical fiber, and the third single-mode optical fiber is Fujikura 60s, and the program is set to standard fusion splicing.

[0010] Furthermore, the detachable dropper is inserted into the circular hole in the middle of the top of the constant temperature and humidity box to drip liquid. After the dripping of liquid is completed, the detachable dropper is taken out and the circular hole is closed.

[0011] Furthermore, the glass slide is taken out from the top of the constant temperature and humidity chamber to clean the residual liquid on the glass slide, and the clean glass slide is placed on the vertical displacement stage.

[0012] Furthermore, the third single-mode optical fiber is subjected to a sensitization pretreatment, and the optical fiber is subjected to a hydrogen loading pretreatment: the third single-mode optical fiber is sealed in a hydrogen reactor with high pressure, strength and temperature, and the photosensitive portion is heated.

[0013] Furthermore, the method of writing the tilted fiber Bragg grating by the third single-mode optical fiber phase mask method is as follows: the ultraviolet incident light passes through a reflector at an angle of 45° to the direction of the incident light, is focused by a focusing lens onto a phase mask template and irradiates the photosensitive optical fiber, and then the phase mask template and the third single-mode optical fiber loaded with hydrogen are fixed in parallel on an angle adjustment frame, and the angle between the phase mask template and the ultraviolet incident light is adjusted to form the tilted fiber Bragg grating.

[0014] The method for simultaneously monitoring changes in multiple parameters based on a multi-resonance fiber Bragg grating multi-parameter sensing device described in the present invention is to turn on a broadband light source, a polarization controller, a constant temperature and humidity chamber, and a spectrum analyzer. The output light of the broadband light source passes through the polarization controller and enters the third single-mode optical fiber through the first single-mode optical fiber. Since there is a certain angle between the inclined fiber Bragg grating in the third single-mode optical fiber and the optical fiber axis, there is both self-backward coupling of the core mode and multiple backward couplings between the core mode and the cladding mode during the light transmission process. After phase matching, a comb-shaped cladding mode is formed. When the external environment temperature changes, the refractive index and concentration of the external material in the cladding change, and the excited cladding mode will produce a wavelength drift. In order to simultaneously monitor the changes in these parameters to be measured, a polarization controller is used to control the polarization direction of the transmitted light. The Bragg mode is represented by λ co , cladding mode interference is represented by λ cl , then the transmission mode λ co , cl It can be expressed as: in is the effective refractive index of the single-mode fiber core, is the effective refractive index of the cladding mode, ∧ TFBG is the period of the interference pattern divided by the cosine of the angle at which the fiber Bragg grating is tilted.

[0015] When a single parameter changes, the output light of the tilted fiber Bragg grating in the third single-mode fiber is transmitted through the second single-mode fiber to the spectrum analyzer to obtain the spectral response of the corresponding parameter. The wavelength drift caused by strain, temperature and refractive index can be obtained by analyzing the transmission mode in the spectrum. The parameter sensitivity is obtained by fitting the resonant wavelength drift with the slope of the parameter change. The parameter sensitivity coefficient can be calculated by fitting the ratio of the parameter sensitivity to the resonant wavelength when no parameter is applied. Each parameter sensitivity coefficient constitutes a sensitivity coefficient matrix. The relationship between the relative wavelength drift of the multi-order cladding mode of the multi-resonant fiber grating caused by the multi-parameter change, the sensitivity coefficient matrix and the multi-parameter change is as follows: Where K is the sensitivity coefficient matrix, x is the external parameter, n is the number of sensitivity coefficients of a single parameter, m is the number of parameters, n≥m, K ij is the sensitivity coefficient corresponding to the i-th cladding mode of the j-th parameter to be measured, Δλ i / λ i is the wavelength drift of the i-th cladding resonance of the multi-resonant fiber Bragg grating caused by parameter change divided by the i-th cladding resonance wavelength without applying parameters.

[0016] When multiple parameters are sensed simultaneously, the third single-mode optical fiber is placed in the object to be measured. The ambient temperature of the object to be measured will change. The temperature change will cause the refractive index and concentration of the object to be measured to change, thereby producing an obvious wavelength drift. By monitoring the wavelength drift of the multi-order cladding mode, the changes of each parameter to be measured can be inferred at the same time according to the sensitivity coefficient matrix established above, thereby realizing a multi-parameter sensing method, namely:

[0017] Compared with the prior art, the present invention has the following beneficial effects: the expansion of the optical fiber sensor market has greatly promoted the demand for multi-parameter sensing of optical fiber sensors. Existing research mainly focuses on the research of dual-parameter optical fiber sensors, among which dual-parameter optical fiber sensors that simultaneously measure temperature and refractive index are reported the most. The method disclosed in the present invention is based on the high-density resonance spectrum of a multi-resonance optical fiber grating, and uses dozens of cladding resonances of a multi-resonance optical fiber sensing structure to measure multiple parameters, breaking through the actual application of traditional multi-resonance optical fiber sensors that only use a single or a few resonances for dual-parameter sensing, greatly enhancing the measurement accuracy, combining the characteristics of different resonances being independent of each other, establishing a multi-parameter sensitivity coefficient matrix based on multi-resonance, and realizing multi-parameter simultaneous sensing. The number of parameters to be measured is consistent with the number of columns of the sensitivity coefficient matrix, and the number of columns of the sensitivity coefficient matrix depends on the number of spectral responses of the multi-resonance optical fiber grating collected in the experiment under multi-parameter changes such as temperature, strain, refractive index, pressure, bending, etc., which provides a simple, reliable, and high-precision new method for multi-parameter sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a multi-parameter sensing device of a multi-resonance fiber Bragg grating of the present invention;

[0019] Figure 2 is a schematic diagram of the structure of a tilted fiber Bragg grating;

[0020] Figure 3 It is a transmission spectrum diagram of the tilted fiber Bragg grating of the present invention under different temperatures, strains and external refractive indices at the same time. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, a detailed description is given below in conjunction with the accompanying drawings and implementation examples.

[0022] like Figure 1-3 As shown, the present invention discloses a multi-parameter sensing device based on multi-resonance fiber grating, which is characterized by: comprising a broadband light source 1, a polarization controller 2, a first single-mode optical fiber 3, a second single-mode optical fiber 4, a third single-mode optical fiber 5, a support rod 6, a horizontal displacement stage 7, a vertical displacement stage 8, a slide 9, a first two-dimensional optical fiber clamp 10, a second two-dimensional optical fiber clamp 11, a detachable dropper 14, a constant temperature and humidity chamber 12 and a spectrum analyzer 13; the left end of the polarization controller 2 is connected to the broadband light source 1, the right end of the polarization controller 2 is connected to the left end of the first single-mode optical fiber, the right end of the first single-mode optical fiber is connected to the left end of the third single-mode optical fiber 5, the left end of the second single-mode optical fiber 4 is connected to the right end of the third single-mode optical fiber 5, and the right end of the second single-mode optical fiber 4 is connected to the spectrum analyzer 13.

[0023] Furthermore, the fiber fusion splicer model used for connecting the first single-mode optical fiber 3, the second single-mode optical fiber 4, and the third single-mode optical fiber 5 is Fujikura 60s, and the program is set to standard fusion splicing.

[0024] Furthermore, the broadband light source 1 operates in the near-infrared band and is a continuous light source with a scanning range of 1515nm-1615nm.

[0025] Furthermore, the detachable dropper 14 extends from the circular hole in the middle of the top of the constant temperature and humidity box 12 and faces the glass slide 9, drips liquid on the glass slide 9, and after completion, takes out the detachable dropper 14 and closes the circular hole.

[0026] Furthermore, the glass slide 9 is taken out from the top of the constant temperature and humidity chamber 12 to clean the residual liquid on the glass slide 9, and the clean glass slide 9 is placed on the vertical displacement stage 8.

[0027] Furthermore, the third single-mode optical fiber 5 is subjected to a sensitivity enhancement pretreatment, and the optical fiber is subjected to a hydrogen loading pretreatment: the third single-mode optical fiber 5 is sealed in a hydrogen reactor with high pressure, strength and temperature, and the photosensitive part is heated.

[0028] Furthermore, the method of writing the tilted fiber Bragg grating 15 into the third single-mode optical fiber 5 by the phase mask method is as follows: the incident ultraviolet light passes through a reflector at an angle of 45° to the direction of the incident light, is focused by a focusing lens onto a phase mask template and irradiates the photosensitive optical fiber, and then the phase mask template and the hydrogen-loaded third single-mode optical fiber 5 are fixed in parallel on an angle adjustment frame, and the angle between the phase mask template and the incident ultraviolet light is adjusted to form the tilted fiber Bragg grating 15.

[0029] The present invention discloses a sensing method of a multi-parameter sensing device based on a multi-resonance fiber Bragg grating. A broadband light source 1, a polarization controller 2, a constant temperature and humidity chamber 12, and a spectrum analyzer 13 are turned on. The output light of the broadband light source 1 passes through the polarization controller 2 and enters the third single-mode optical fiber 5 through the first single-mode optical fiber 3. Since there is a certain angle between the inclined fiber Bragg grating 15 in the third single-mode optical fiber 5 and the optical fiber axis, there is self-backward coupling of the core mode and multiple backward couplings between the core mode and the cladding mode during the light transmission process. After phase matching, a comb-shaped cladding mode is formed. When the external environment temperature changes, the refractive index and concentration of the external material in the cladding change, and the excited cladding mode will produce a wavelength drift. In order to simultaneously monitor the changes in these parameters to be measured, a polarization controller is used to control the polarization direction of the transmitted light. The Bragg mode is represented by λ co , cladding mode interference is represented by λ cl , then the transmission mode λ co , cl It can be expressed as: in is the effective refractive index of the single-mode fiber core, is the effective refractive index of the cladding mode, ∧ TFBG is the period of the interference pattern divided by the cosine of the angle at which the fiber Bragg grating is tilted.

[0030] When a single parameter changes, the output light of the broadband light source 1 passes through the polarization controller 2 and enters the third single-mode optical fiber 5 through the first single-mode optical fiber 3. Since the multi-order cladding modes of the tilted fiber Bragg grating 15 in the third single-mode optical fiber 5 have different sensitivities to strain, temperature and refractive index, the temperature change of the constant temperature and humidity chamber 12, the moving distance of the horizontal displacement stage 7 and the different refractive index liquids added by the detachable dropper 14 are controlled respectively to ensure the changes of temperature, strain and refractive index in turn, and the output light is transmitted through the second single-mode optical fiber 4 to the spectrum analyzer 13 to obtain the spectral response of the corresponding parameter. By analyzing the transmission mode in the spectrum, the wavelength drift of the multi-order cladding mode caused by temperature, strain and refractive index can be obtained. The parameter sensitivity of the resonant wavelength can be obtained by fitting the resonant wavelength drift with the slope of the parameter change. Then, the parameter sensitivity coefficient K can be calculated by fitting the ratio of the parameter sensitivity to the resonant wavelength when no parameter is applied. ij , ensure that the number of temperature, strain and refractive index sensitivity coefficients is the same, establish the n×m sensitivity coefficient matrix K, the relationship between the relative wavelength drift of the multi-order cladding mode of the multi-resonant fiber Bragg grating caused by the multi-parameter change, the sensitivity coefficient matrix and the multi-parameter change is: Where K is the sensitivity coefficient matrix, x is the external parameter, n is the number of sensitivity coefficients of a single parameter, m is the number of parameters, n ≥ m, in this implementation case, the simultaneous monitoring of the three parameters of temperature, strain and refractive index is achieved, so m = 3. K ij is the sensitivity coefficient corresponding to the i-th cladding mode of the j-th parameter to be measured, Δλ i / λ i is the wavelength drift of the i-th cladding resonance of the multi-resonant fiber Bragg grating caused by parameter change divided by the i-th cladding resonance wavelength without applying parameters.

[0031] When multiple parameters are sensed simultaneously, the third single-mode optical fiber 5 is placed in the object to be measured, so that the temperature of the surrounding environment where the object to be measured is changed. The temperature change will change the refractive index of the object to be measured, thereby causing an obvious wavelength drift, such as Figure 3 As shown, different temperatures cause the measured multi-order cladding modes to drift accordingly. Different temperatures will affect the refractive index change of the object to be measured and the length change of the tilted fiber grating 15 in the third single-mode optical fiber 5. The spectrum response is obtained by the spectrum analyzer 15, and the wavelength drift of the multi-order cladding mode is monitored. The changes in temperature, strain and refractive index are inferred from the sensitivity coefficient matrix K established above, and a multi-parameter sensing method is realized, namely:

[0032] In summary, the tilted fiber Bragg grating 15 in the third single-mode optical fiber 5 can reversely couple the input light from the optical fiber core to the cladding and maintain a certain mechanical strength, calibrate the multi-resonance sensitivity and sensitivity coefficient of each parameter of the multi-resonance fiber grating, establish a sensitivity coefficient matrix, and monitor the wavelength drift of the tilted fiber Bragg grating 15 to simultaneously infer the changes in multiple parameters.

[0033] The multi-parameter sensing device and method based on multi-resonance fiber Bragg grating realizes the simultaneous sensing of multiple parameters and has the advantages of simple production, small size, high sensitivity and low cost. At the same time, the developed device is based on a single multi-resonance fiber Bragg grating and does not involve the use of multiple gratings or the application of special coatings. The structure is simple, compact, stable and strong, which is conducive to the simultaneous sensing of multiple parameters.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the technical solutions of the present invention have been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-parameter sensing device based on multi-resonance fiber Bragg grating, characterized in that: The invention comprises a broadband light source (1), a polarization controller (2), a first single-mode optical fiber (3), a second single-mode optical fiber (4), a third single-mode optical fiber (5), a support rod (6), an X-axis displacement stage (7), a Z-axis displacement stage (8), a glass slide (9), a first two-dimensional optical fiber clamp (10), a second two-dimensional optical fiber clamp (11), a detachable dropper (14), a constant temperature and humidity chamber (12) and a spectrum analyzer (13); the left end of the polarization controller (2) is connected to the broadband light source (1), the right end of the polarization controller (2) is connected to the left end of the first single-mode optical fiber (3), the right end of the first single-mode optical fiber (3) is connected to the left end of the third single-mode optical fiber (5), the left end of the second single-mode optical fiber (4) is connected to the right end of the third single-mode optical fiber (5), and the right end of the second single-mode optical fiber (4) is connected to the spectrum analyzer (13).

2. The multi-parameter sensing device based on multi-resonance fiber Bragg grating according to claim 1, characterized in that: The broadband light source (1) operates in the near-infrared band and is a continuous light source with a scanning range of 1515nm-1615nm.

3. The multi-parameter sensing device based on multi-resonance fiber Bragg grating according to claim 2, characterized in that: The core of the third single-mode optical fiber (5) is written with the tilted optical fiber grating (15), the grating length is 10 mm, and the tilt angle is 10°.

4. The multi-parameter sensing device based on multi-resonance fiber Bragg grating according to claim 3, characterized in that: The third single-mode optical fiber (5) is subjected to a sensitization pretreatment, and the optical fiber is subjected to a hydrogen loading pretreatment: the third single-mode optical fiber (5) is sealed in a hydrogen reaction kettle with high pressure, strength and temperature, and the photosensitive part is heated.

5. The multi-parameter sensing device based on multi-resonance fiber Bragg grating according to claim 4, characterized in that: The method of writing the tilted fiber grating (15) into the third single-mode optical fiber (5) by the phase mask method is as follows: the incident ultraviolet light passes through a reflector at an angle of 45 degrees to the incident light direction, is focused by a focusing lens onto a phase mask template and irradiates the photosensitive optical fiber, and then the phase mask template and the third single-mode optical fiber (5) loaded with hydrogen are fixed in parallel on an angle adjustment frame, and the angle between the phase mask template and the incident ultraviolet light is adjusted to form the tilted fiber grating (15).

6. The multi-parameter sensing method based on multi-resonance fiber Bragg grating according to claim 5, characterized in that: There is a certain angle between the tilted fiber Bragg grating (15) in the third single-mode optical fiber (5) and the optical fiber axis, so that in the process of light transmission, there is self-backward coupling of the core mode, multiple backward coupling between the core mode and the cladding mode, and a comb-shaped cladding mode is formed after phase matching. The change of the measured parameter will cause the multi-resonance wavelength drift of the tilted fiber Bragg grating (15) in the third single-mode optical fiber (5). The polarization direction of the transmitted light is controlled by a polarization controller. The transmission mode λ of the Bragg and cladding resonances co , cl Respectively expressed as:

7. The multi-parameter sensing method based on multi-resonance fiber Bragg grating according to claim 6, characterized in that: The multi-resonance fiber grating is written by the same method, and the experiment collects the spectral response of the multi-parameter P and S states of the multi-resonance fiber grating.

8. The multi-parameter sensing method based on multi-resonance fiber Bragg grating according to claim 7, characterized in that: When a single parameter changes, the broadband light source (1), the polarization controller (2), the constant temperature and humidity chamber (12) and the spectrum analyzer (13) are turned on, and the output light of the broadband light source (1) passes through the polarization controller (2) and enters the third single-mode optical fiber (5) through the first single-mode optical fiber (3). Since the multi-order cladding mode of the tilted fiber grating (15) in the third single-mode optical fiber (5) is sensitive to parameters such as strain, temperature and refractive index, by controlling the changes of different parameters, the output light is transmitted through the second single-mode optical fiber (4) to the spectrum analyzer (13) to obtain a spectral response, and the wavelength drift caused by the parameters such as strain, temperature and refractive index can be obtained by analysis; The parameter sensitivity Δλ of each selected resonant wavelength is obtained by fitting the slope of the extracted resonant wavelength and the applied parameter. i , and then normalize the sensitivity coefficient, that is, the parameter sensitivity is divided by the corresponding resonant wavelength Δλ when no parameter is applied i / λ i , calculate the parameter sensitivity coefficient K of the corresponding resonant wavelength ij ; Establish an n×m sensitivity coefficient matrix, where n is the number of sensitivity coefficients of a parameter, m represents the number of parameters, and the number of resonances is greater than or equal to the number of parameters to be measured, that is, n≥m; The relationship between the relative wavelength drift of the multi-order cladding modes of the multi-resonant fiber Bragg grating caused by the multi-parameter change, the sensitivity coefficient matrix and the multi-parameter change is:

9. The multi-parameter sensing method based on multi-resonance fiber Bragg grating according to claim 8, characterized in that: When multiple parameters are sensed simultaneously, the third single-mode optical fiber (5) is placed in the object to be measured. The temperature of the surrounding environment of the object to be measured will change. The temperature change will cause the refractive index, concentration, etc. of the object to be measured to change, thereby generating an obvious wavelength drift. By monitoring the wavelength drift of the multi-order cladding mode, the changes of each parameter to be measured are simultaneously inferred based on the established sensitivity coefficient matrix K, thereby realizing a multi-parameter sensing method, that is:

10. The multi-parameter sensing method based on multi-resonance fiber Bragg grating according to claim 9, characterized in that: The sensitivity coefficient matrix K established can be used in multi-resonance fiber Bragg gratings with the same writing method to achieve independent and simultaneous measurement of multiple physical or chemical parameters, solving the problem that most unresolved application sensors need to be located in an uncontrolled environment, and temperature and strain may affect the calibration of the sensor or the chemical process being monitored.

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