Two-parameter optical fiber sensor and two-parameter optical fiber sensor measuring method

Abstract

The invention provides an optical fiber sensor, and relates to the field of optical fiber sensors, the optical fiber sensor comprises a light source, an optical fiber sensing structure, a transmission optical fiber, an optical fiber coupler and an optical spectrum analyzer, the optical fiber sensing structure comprises a single-mode optical fiber, a PDMS film, an F-P cavity, an FBG and a magnetostrictive element; one end of the single-mode optical fiber is connected with the PDMS thin film through a capillary tube, air is filled between the end face of the single-mode optical fiber and the PDMS thin film, and an F-P cavity is formed between an interface M1 formed by the single-mode optical fiber and the air and an interface M2 formed by the PDMS thin film and the air; the FBG is connected to the magnetostrictive element, and when a magnetic field is applied, the telescopic change of the magnetostrictive element influences the grating period of the FBG and further influences the wavelength in the FBG; through the sensitivity of each part of the sensor to the temperature and the magnetic field, the temperature sensitivity and the magnetic field sensitivity of the optical wavelength in the F-P cavity and the temperature sensitivity and the magnetic field sensitivity of the optical wavelength in the FBG are independently calculated, correlation coefficients are calculated, and synchronous two-parameter measurement of the magnetic field and the temperature is realized.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensors, and in particular to a dual-parameter optical fiber sensor and a dual-parameter optical fiber sensor measurement method. Background Art

[0002] Compared with traditional magnetic field detection technology, fiber optic magnetic field sensors have the advantages of small size, low cost, anti-electromagnetic interference, and chemical corrosion resistance. The most common principles of magnetic field sensing technology are magneto-optical effect and magnetostriction. The basic principle of fiber optic sensors based on this type of magnetic sensitive material is to transfer the longitudinal strain or induced refractive index change generated under the action of the magnetic field to the fiber optic sensing system. Among them, fiber optic magnetic field sensors based on magnetostrictive materials have been proposed for decades. Magnetostrictive material is a ferromagnetic material that deforms during magnetization. It can be designed for magnetic field or current sensing by directly coating a magnetostrictive film or bonding it with a magnetostrictive material.

[0003] FBG (Fiber Bragg Grating), also known as Fiber Bragg Grating, is widely used in the fields of fiber optic communication and fiber optic sensors. The principle is to regularly engrave the same high refractive index interval area on a section of the fiber core or sleeve in the optical fiber to form a light wave reflector. When the incident light wave passes through the fiber core or sleeve, a part of the light wave will be reflected back and form a light wave reflected by the fiber core or sleeve. The wavelength of this reflected light wave is related to the grating period and the refractive index of the fiber. Depending on the grating period, the wavelength of the reflected light wave will also be different. Therefore, the environmental changes to the optical fiber, such as temperature and strain, can be inferred by detecting the change in the wavelength of the reflected light wave.

[0004] At present, most optical fiber sensors realize single parameter measurement, such as optical fiber magnetic field sensors, optical fiber temperature sensors, and optical fiber strain sensors. Invention patent: Temperature and strain dual parameter optical fiber sensor based on optical fiber FP cavity (Fabry-Pérot cavity) cascade FBG structure, discloses temperature and strain dual parameter optical fiber sensor with optical fiber FP cavity cascade FBG structure, realizing temperature and strain dual parameter measurement. However, there are few optical fiber sensors on the market that can measure magnetic field and temperature at the same time. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes to design a new optical fiber sensor and measurement method for dual parameters of temperature and magnetic field by utilizing the magnetic sensitivity of magnetostrictive materials and the temperature sensitivity of polydimethylsiloxane (PDMS).

[0006] A dual-parameter optical fiber sensor, comprising: a light source, an optical fiber sensing structure, a transmission optical fiber, an optical fiber coupler, and an optical spectrum analyzer, wherein the optical fiber sensing structure comprises a single-mode optical fiber, a PDMS film, an FP cavity, an FBG, and a magnetostrictive element;

[0007] One end of the single-mode optical fiber and the PDMS film are connected by a capillary, and air is filled between the end face of the single-mode optical fiber and the PDMS film, an interface M1 formed by the single-mode optical fiber and the air, an interface M2 formed by the PDMS film and the air, and an FP cavity is formed between M1 and M2;

[0008] The FBG is connected to a magnetostrictive element. When a magnetic field is applied, the expansion and contraction changes of the magnetostrictive element affect the grating period of the FBG and thus affect the wavelength in the FBG.

[0009] When the incident light L in The incident light L is transmitted to the first port of the fiber coupler through the transmission fiber. in When transmitted to the single-mode optical fiber through the second port of the optical fiber coupler, a part of it is reflected by the FBG to obtain reflected light L1, and the reflected light L1 is received by the optical spectrum analyzer through the third port of the optical fiber coupler. in The other part of the transmitted light L2 reaches the FP cavity, and generates interference light L3 through the interface M1 and the interface M2. The interference light L3 returns through the FBG and is output. The final output light is composed of L1 and L3.

[0010] The temperature sensitivity and magnetic field sensitivity of the light wavelength change in the FP cavity, the temperature sensitivity and magnetic field sensitivity of the light wavelength change in the FBG are calculated, and the correlation coefficient is calculated to achieve synchronous dual-parameter measurement of temperature and magnetic field.

[0011] Furthermore, the interface formed by the PDMS film and the air is arc-shaped.

[0012] Furthermore, the FP cavity length is 132 um and the PDMS film thickness is 54 um.

[0013] Furthermore, the sensor output intensity is expressed as:

[0014] I out =I in [f B +(1-f B ) 2 f P ]

[0015]

[0016]

[0017] λB =2n B Λ

[0018] Among them, I out Indicates the intensity of light output by the sensor, I in Indicates the intensity of the sensor input light, f B is the reflection coefficient of FBG, f P is the reflection coefficient of the FP cavity, R B is the reflectivity of FBG, λ is the wavelength of incident light, and λ B is the central wavelength of FBG, B is the bandwidth of FBG reflection peak, R P is the reflectivity of the FP cavity reflection end, n is the refractive index of air, L is the length of the FP cavity, n B represents the FBG core refractive index, and Λ represents the period of the grating.

[0019] Furthermore, under a stable magnetic field, the sensitivity of the wavelength change of light in the FP cavity to temperature change is:

[0020] Δλ P =K PT ΔT

[0021] Among them, K PT represents the temperature sensitivity coefficient of the FP cavity, and ΔT represents the temperature change;

[0022] At a stable temperature, the sensitivity of the wavelength change of light in the FP cavity to the change of magnetic field intensity is:

[0023] Δλ P =K PH ΔH

[0024] Among them, Δλ P represents the wavelength change of light in the FP cavity, K PH is the magnetic field sensitivity coefficient of the FP cavity, and ΔH is the change in magnetic field intensity.

[0025] Furthermore, at a stable temperature, the wavelength variation in the FBG depends only on the applied magnetic field strength:

[0026] Δλ B =K BH C L ΔH

[0027] Among them, K BH The magnetic field sensitivity coefficient of the wavelength of light in the FBG, C L It represents the amount of expansion and contraction of the magnetostrictive element when a magnetic field is applied, and ΔH represents the magnetic field strength;

[0028] Under a stable magnetic field, the wavelength change of light in the FBG is only related to the temperature change:

[0029] Δλ B =K BT ΔT

[0030] Among them, Δλ B represents the wavelength change of light in FBG, K BT It represents the temperature sensitivity coefficient of the wavelength of light in FBG, and ΔT represents the temperature change.

[0031] Similarly, under a stable magnetic field, the temperature sensitivity coefficient K of the wavelength of light in the FBG is obtained: BT .

[0032] Furthermore, the sensitivity matrix is ​​constructed

[0033]

[0034] By calculating the changes in temperature and magnetic field, we can find the magnitude of temperature and magnetic field:

[0035]

[0036] M=K PT K BH -K PH K BT

[0037] Among them, K BH K represents the magnetic field sensitivity coefficient of the wavelength of light in the FBG. PH represents the magnetic field sensitivity coefficient of the FP cavity, K PT represents the temperature sensitivity coefficient of the FP cavity, K BT It represents the temperature sensitivity coefficient of the wavelength of light in the FBG.

[0038] The present invention also proposes a dual-parameter optical fiber sensor measurement method, characterized in that it is implemented based on the optical fiber temperature and magnetic field dual-parameter sensor according to any one of claims 1 to 7, comprising: an incident light L emitted by a light source in The incident light L is transmitted to the first port of the fiber coupler through the transmission fiber. in When transmitted to the single-mode optical fiber through the second port of the optical fiber coupler, a part of it is reflected by the FBG to obtain reflected light L1, and the reflected light L1 is received by the optical spectrum analyzer through the third port of the optical fiber coupler. in The other part of the transmitted light L2 reaches the FP cavity, and generates interference light L3 through the interface M1 and the interface M2. The interference light L3 returns through the FBG and is output. The final output light is composed of L1 and L3.

[0039] The magnetic field sensitivity and temperature sensitivity of the light wavelength in the FP cavity, the temperature sensitivity and magnetic field sensitivity of the light wavelength in the FBG are calculated separately, and the correlation coefficient is calculated to achieve synchronous dual-parameter measurement of magnetic field and temperature.

[0040] The beneficial effects brought by the technical solution provided by the present invention are:

[0041] The present invention proposes an optical fiber sensing structure based on the cascade connection of FP cavity, FBG and magnetostrictive element, calculates the temperature sensitivity and magnetic field sensitivity of the light wavelength in the FP cavity separately, and the temperature sensitivity and magnetic field sensitivity of the light wavelength of the FBG connected with the magnetostrictive element, calculates the correlation coefficient, and realizes the dual parameter measurement of temperature and magnetic field. The sensor has a simple structure and is easy to manufacture. It can effectively avoid temperature cross sensitivity when measuring magnetic field, and has broad application prospects in electromagnetic field measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a structural diagram of an optical fiber sensor according to an embodiment of the present invention;

[0043] Figure 2 is a diagram of an experimental setup of an optical fiber sensor according to an embodiment of the present invention;

[0044] Figure 3 is a spectrum diagram of different temperatures under the experimental device of the optical fiber sensor of the embodiment of the present invention, wherein: Figure 3 (a) is the reflection spectrum when the temperature rises from 30℃ to 90℃. Figure 3 (b) is the corresponding amplified reflection spectrum of the wavelength of light in the FBG;

[0045] Figure 4 is a fitting curve of experimental data of the interference light wavelength of FP and the wavelength of the intermediate light of FBG when the temperature rises from 30°C to 90°C under the experimental device of the optical fiber sensor of the embodiment of the present invention, wherein Figure 4 (a) is the experimental data fitting curve of the interference light wavelength of FP when the temperature rises from 30℃ to 90℃. Figure 4 (b) is the experimental data fitting curve of the wavelength of the medium light of FBG when the temperature rises from 30℃ to 90℃;

[0046] Figure 5 is the response sensitivity of the wavelength of light in FBG and the magnetic field intensity of the interference light wavelength in FP under the experimental device of the optical fiber sensor of the embodiment of the present invention, wherein, Figure 5 (a) is the response sensitivity of the FBG to the magnetic field intensity of the wavelength of light. Figure 5 (b) is the response sensitivity of the magnetic field intensity of the interference light wavelength in FP. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0048] The optical fiber sensing structure of the embodiment of the present invention is shown in FIG. Figure 1 , specifically including:

[0049] Light source, fiber optic sensing structure, transmission fiber, fiber optic coupler, optical spectrum analyzer.

[0050] The optical fiber sensing structure includes single-mode optical fiber, PDMS film, FP cavity, FBG, and magnetostrictive element;

[0051] One end of the single-mode optical fiber and the PDMS film are connected by a capillary, and air is filled between the end face of the single-mode optical fiber and the PDMS film. Since the refractive indices of the single-mode optical fiber, air and PDMS film are different, the single-mode optical fiber and the air form an interface M1, and the PDMS film and the air form an interface M2. The interfaces M1 and M2 are almost parallel, and a Fabry-Perot interferometer is formed between the interfaces M1, M2, and M1 and M2, namely, an FP cavity (Fabry-Perot cavity).

[0052] Polydimethylsiloxane (PDMS) is an excellent temperature sensing material composed of an elastic polymer (Sylgard184-A) and a curing agent (Sylgard184-B). It not only has good thermal expansion and thermo-optical properties but also has good adhesion. The initial state of PDMS is liquid, and it gradually becomes solid after exceeding a certain temperature. Therefore, PDMS can be easily and cleverly integrated with optical fibers to create an excellent temperature sensing system. Due to the good temperature characteristics of PDMS, the sensitivity of related optical fiber temperature sensors can be greatly improved.

[0053] Since the initial state of PDMS is liquid and there is the influence of surface tension during the curing process, the interface formed by the PDMS film and the air is arc-shaped.

[0054] FBG can be designed for magnetic field or current sensing by directly coating magnetostrictive films or bonding with magnetostrictive materials. In this way, the strain generated in the magnetostrictive material by an applied magnetic field can be transferred to the FBG. Terfenol-D is the most ideal giant magnetostrictive material due to its large magnetostriction coefficient, high reliability, fast response speed and wide temperature range. For magnetic field sensors based on Terfenol-D and FBG, the magnetostrictive effect of Terfenol-D causes the Bragg wavelength of FBG to shift. However, FBG and magnetostrictive materials are greatly affected by temperature, which may make it difficult to distinguish between magnetic field and temperature. This temperature cross-sensitivity can be eliminated by introducing an additional fiber Fabry-Perot (FP) interferometer (i.e., FP cavity) that is small and easy to integrate.

[0055] The transmission path of the light source in the optical fiber sensor is: when the incident light L emitted by the light source in The incident light L is transmitted to the first port of the fiber coupler through the transmission fiber. in When transmitted to the single-mode optical fiber through the second port of the optical fiber coupler, a part of it is reflected by the FBG to obtain reflected light L1, which is received by the optical spectrum analyzer through the third port of the optical fiber coupler. in The other part of the transmitted light L2 reaches the FP cavity, and generates interference light L3 through the interface M1 and the interface M2. The interference light L3 returns through the FBG and is output. The final output light is composed of L1 and L3.

[0056] Due to the low reflectivity of the optical fiber and polymer surface, the effect of multiple reflections can be ignored, and the intensity of the output light of the FP cavity is expressed as:

[0057] I out =I in [f B +(1-f B ) 2 f P ]

[0058]

[0059]

[0060] λ B =2n B Λ

[0061] Among them, I out Indicates the intensity of light output by the sensor, I in Indicates the intensity of the sensor input light, f B is the reflection coefficient of FBG, f P is the reflection coefficient of the FP cavity, R B is the reflectivity of FBG, λ is the wavelength of incident light, and λ B is the central wavelength of FBG, B is the bandwidth of FBG reflection peak, R P is the reflectivity of the FP cavity reflection end, n is the refractive index of air, L is the length of the FP cavity, n B represents the FBG core refractive index, and Λ represents the period of the grating.

[0062] The resonant wavelength in the interference spectrum within the FP cavity is expressed as:

[0063]

[0064] Wherein, n is the refractive index of air, L is the length of the FP cavity, and m represents a positive integer, m=1, 2, 3, ...

[0065] When the sensor is placed in different temperature and magnetic field environments, the cured PDMS will expand or contract, changing the length of the FP cavity, thereby causing the wavelength of the interference light to change. Under a stable magnetic field, the sensitivity of the wavelength change of the light in the FP cavity to temperature change is:

[0066] Δλ P =K PT ΔT

[0067] At a stable temperature, the sensitivity of the wavelength change of light in the FP cavity to the change of magnetic field intensity is:

[0068] Δλ P =K PG ΔH

[0069] Among them, Δλ P represents the wavelength change of light in the FP cavity, K PT represents the temperature sensitivity coefficient of the FP cavity, ΔT represents the temperature change, K PH is the magnetic field sensitivity coefficient of the FP cavity, and ΔH is the change in magnetic field intensity.

[0070] The main factors affecting the central wavelength of fiber Bragg grating are the elastic-optic effect, the thermo-optic effect and the thermal expansion effect. In the sensing system, FBG is combined with a magnetostrictive element (Terfenol-D rod). Once a magnetic field is applied to the structure, the elastic element will be stretched and transferred to the grating area, thereby affecting the grating period, which is reflected as a change in wavelength. Under fixed temperature and fixed stress, according to the strain transfer theory, the change wavelength of FBG can be expressed as:

[0071] Δλ B =(1-P c )Δε1λ B

[0072] Among them, Δλ B represents the wavelength change of light in FBG, P c represents the optical tensor, Δε1 represents the strain of the magnetostrictive element caused by the change of magnetic field, and λ B is the central wavelength of the FBG;

[0073] FBG is connected to a magnetostrictive element. When a magnetic field is applied, the stretching change of the magnetostrictive element affects the grating period of the FBG and thus affects the wavelength of light in the FBG. The wavelength change in the FBG is related to the temperature change and the change in the magnetic field strength. At a stable temperature, the wavelength change in the FBG is only related to the applied magnetic field strength:

[0074] Δλ B =K BH C L ΔH

[0075] Similarly, under a stable magnetic field, the wavelength change in the FBG is only related to the applied magnetic field strength:

[0076] Δλ B =K BT ΔT

[0077] Get the temperature sensitivity coefficient K of the wavelength of light in FBG BT .

[0078] Δλ B =K BH C L ΔH+K BT ΔT

[0079] Among them, Δλ B represents the wavelength change of light in FBG, K BH , K BT They represent the sensitivity coefficient of the wavelength of light in FBG to the magnetic field change and the temperature change, respectively. L It represents the expansion and contraction volume of the magnetostrictive element when a magnetic field is applied, and ΔH and ΔT represent the magnetic field strength and temperature change, respectively.

[0080] The final spectrum of the sensor is the superposition of the FBG reflection spectrum and the FP interference spectrum. By measuring the wavelength change of the interference peak and the central wavelength shift of the FBG, the magnetic field and temperature can be measured simultaneously.

[0081] Constructing the sensitivity matrix

[0082]

[0083] Find the change in temperature and magnetic field:

[0084]

[0085] M=K PT K BH C L -K PH K BT

[0086] The values ​​of temperature and magnetic field changes are obtained, and then the temperature and magnetic field are obtained.

[0087] A dual-parameter optical fiber sensor measurement method based on the optical fiber sensor includes: an incident light L emitted by a light source in The incident light L is transmitted to the first port of the fiber coupler through the transmission fiber. inWhen transmitted to the single-mode optical fiber through the second port of the optical fiber coupler, a part of it is reflected by the FBG to obtain reflected light L1, which is received by the optical spectrum analyzer through the third port of the optical fiber coupler. in The other part of the transmitted light L2 reaches the FP cavity, and generates interference light L3 through the interface M1 and the interface M2. The interference light L3 returns through the FBG and is output. The final output light is composed of L1 and L3.

[0088] The temperature sensitivity and magnetic field sensitivity of the light wavelength change in the FP cavity, the temperature sensitivity and magnetic field sensitivity of the light wavelength change in the FBG are calculated, and the correlation coefficient is calculated to realize the synchronous dual parameter measurement of magnetic field and temperature.

[0089] Experimental preparation:

[0090] With the help of a microscope, a section of FBG single-mode fiber was inserted into a capillary with a diameter of 126 μm. The single-mode fiber was fixed to the opening of the glass tube with UV glue. The reflectivity of the commercial FBG is 96%, the grating length is 15 mm, the central wavelength is 1540 nm, and the 3 dB bandwidth is less than 0.03 nm. First, the experimental needle was immersed in a pre-configured PDMS with a volume fraction of 10:1 to obtain a small amount of PDMS, and then the needle was slowly moved to the other end of the capillary, and the PDMS above the fine needle was absorbed into the capillary by the capillary effect. The amount of PDMS in the capillary is difficult to control, so it is necessary to continuously control the test to determine the amount of PDMS on the needle. When the PDMS in the capillary no longer moves, it is placed in a temperature-controlled box and heated and cured at 80 ° C for 2 h. Finally, a FP cavity is formed between the end of the flat single-mode fiber and the cured PDMS film.

[0091] The FBG grating region on the single-mode fiber was glued to the Terfenol-D rod with grooves using UV glue. The length, width and height of the Terfenol-D rod were 20 mm, 5 mm and 5 mm respectively, the width and depth of the groove were both 220 μm, the length of the FP cavity was 132 μm, and the thickness of the PDMS film was 54 μm.

[0092] The FBG is connected to the magnetostrictive material, and the FP cavity is needed to control the effect of temperature on it during the magnetic field characterization process.

[0093] Experimental setup Figure 2 As shown. The ASE light source (10mW in C+L band) is connected to the input port 1 of the 3dB coupler. After the incident light reaches the sensor head through port 2, the reflected light signal is received by the optical spectrum analyzer (OSA, AQ6370C) through port 3. The resolution of OSA is 0.02nm. The device is placed in a temperature-controlled box to adjust the temperature. The central wavelength of the FBG is used as a reference for the FP cavity interferometry spectrum.

[0094] Experimental protocol:

[0095] 1. Temperature sensing

[0096] In order to study the temperature sensing characteristics of the sensor, the sensor probe was placed in a temperature control box with a temperature adjustment resolution of 1°C. The sensor spectrum was continuously recorded from 30°C to 90°C in steps of 10°C. Typical experimental spectra at different temperatures are shown in Figure 1. Figure 3 During the experiment, it was found that after three repeated heating or cooling, the reflectance spectra had a high degree of overlap, which showed that the device had good repeatability.

[0097] from Figure 3 It can be seen that the spectral contrasts of FP and FBG are about 4.60dB and 11.85dB, respectively, and the reflectance spectrum of the cascade sensing structure changes with temperature. As the temperature increases, the reflectance spectrum of FP blue-shifts. However, as the temperature increases, the reflectance spectrum of FBG shifts to the right. The reason for this phenomenon is that PDMS has a negative thermo-optical constant. The maximum wavelength shift of the FP spectrum is about 7.26nm, close to 1550nm ( Figure 3 (marked as point P in (a)).

[0098] The experimental data were further processed to analyze the temperature response characteristics of the sensor, such as Figure 4 As shown. FP(K PT ) is about -121.56pm / C, while FBG (K BT ) has a temperature sensitivity of about 17.68 pm / °C. It can be concluded that the temperature response of FP is better than that of FBG, which is convenient for comparing the effect of temperature on FBG in field characterization.

[0099] 2. Magnetic field sensing

[0100] In order to evaluate the magnetic field sensitivity of the fabricated sensor, the entire sensor was placed at the center of the electromagnetic coil. The magnetic field strength was changed by adjusting the output current. During the magnetic field test, the temperature was controlled at 25°C and the magnetic field strength increased from 0mT to 8mT at intervals of 2mT. Since the reflection spectrum of the cascade sensing structure is greatly affected by temperature changes, it takes a while for the reflection spectrum of the FP cavity to recover and be consistent with the initial spectrum after each increase in the magnetic field. Therefore, each spectral data is recorded when the reflection spectrum is stable. Figure 5 As shown in Figure 1, it can be observed that the central wavelength of FBG increases with the increase of magnetic field intensity. The magnetic field intensity response sensitivity is 21.6.pm / mT. Figure 5 As shown in (b), the interference wavelength of the FP barely shifts, which can be used to calibrate the ambient temperature and then help to accurately record the magnetic field data.

[0101] Then, the synchronous measurement of temperature, strain and magnetic field can be achieved using the Terfenol-D rod integrated with the FP-FBG fiber optic sensor.

[0102] In the embodiment of the present invention, the temperature and magnetic field are mainly measured by experiments. According to the temperature and magnetic field sensitivity obtained by the previous measurement, the calculation matrix of the temperature and magnetic field is obtained:

[0103]

[0104] By measuring the change in the interference peak wavelength of the FP and the shift in the reflection wavelength of the FBG, the temperature and magnetic field magnitude can be obtained simultaneously. Based on the measured temperature and magnetic field sensitivity, it can be inferred that the resolution of the sensor is 1.003°C and 0.069mT respectively.

[0105] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual-parameter optical fiber sensor, comprising: A light source, an optical fiber sensing structure, a transmission optical fiber, an optical fiber coupler, and an optical spectrum analyzer, characterized in that: The optical fiber sensing structure includes a single-mode optical fiber, a PDMS film, an FP cavity, an FBG, and a magnetostrictive element; One end of the single-mode optical fiber and the PDMS film are connected by a capillary, and air is filled between the end face of the single-mode optical fiber and the PDMS film, an interface M1 formed by the single-mode optical fiber and the air, an interface M2 formed by the PDMS film and the air, and an FP cavity is formed between M1 and M2; The FBG is connected to a magnetostrictive element. When a magnetic field is applied, the expansion and contraction changes of the magnetostrictive element affect the grating period of the FBG and thus affect the wavelength in the FBG. When the incident light L in The incident light L is transmitted to the first port of the fiber coupler through the transmission fiber. in When transmitted to the single-mode optical fiber through the second port of the optical fiber coupler, a part of it is reflected by the FBG to obtain reflected light L1, and the reflected light L1 is received by the optical spectrum analyzer through the third port of the optical fiber coupler. in The other part of the transmitted light L2 reaches the FP cavity, and generates interference light L3 through the interface M1 and the interface M2. The interference light L3 returns through the FBG and is output. The final output light is composed of L1 and L3. The temperature sensitivity and magnetic field sensitivity of the light wavelength change in the FP cavity, the temperature sensitivity and magnetic field sensitivity of the light wavelength change in the FBG are calculated, and the correlation coefficient is calculated to achieve synchronous dual-parameter measurement of temperature and magnetic field.

2. A dual-parameter optical fiber sensor according to claim 1, characterized in that: The interface formed by the PDMS film and the air is arc-shaped.

3. A dual-parameter optical fiber sensor according to claim 1, characterized in that: The FP cavity length is 132um and the PDMS film thickness is 54um.

4. A dual-parameter optical fiber sensor according to claim 1, characterized in that: The sensor output intensity is expressed as: I out =I in [f B +(1-f B ) 2 f P ] l B =2n B L Among them, I out Indicates the intensity of light output by the sensor, I in Indicates the intensity of the sensor input light, f B is the reflection coefficient of FBG, f P is the reflection coefficient of the FP cavity, R B is the reflectivity of FBG, λ is the wavelength of incident light, and λ B is the central wavelength of FBG, B is the bandwidth of FBG reflection peak, R P is the reflectivity of the FP cavity reflection end, n is the refractive index of air, L is the length of the FP cavity, n B represents the FBG core refractive index, and Λ represents the period of the grating.

5. A dual-parameter optical fiber sensor according to claim 1, characterized in that: Under a stable magnetic field, the sensitivity of the wavelength change of light in the FP cavity to temperature change is: Dl P =K PT ΔT Among them, Δλ P represents the wavelength change of light in the FP cavity, K PT represents the temperature sensitivity coefficient of the FP cavity, and ΔT represents the temperature change; At a stable temperature, the sensitivity of the wavelength change of light in the FP cavity to the change of magnetic field intensity is: Dl P =K PH ΔH Among them, K PH is the magnetic field sensitivity coefficient of the FP cavity, and ΔH is the change in magnetic field intensity.

6. A dual-parameter optical fiber sensor according to claim 5, characterized in that: At a stable temperature, the wavelength of light in the FBG changes only with the applied magnetic field strength: Dl B =K BH C L ΔH Among them, Δλ B represents the wavelength change of light in FBG, K BH The magnetic field sensitivity coefficient of the wavelength of light in the FBG, C L represents the amount of expansion and contraction of the magnetostrictive element when a magnetic field is applied, and ΔH represents the change in magnetic field intensity; Under a stable magnetic field, the wavelength change of light in the FBG is only related to the temperature change: Dl B =K BT ΔT Among them, K BT It represents the temperature sensitivity coefficient of the wavelength of light in FBG, and ΔT represents the temperature change.

7. A dual-parameter optical fiber sensor according to claim 6, characterized in that: Constructing the sensitivity matrix By calculating the changes in temperature and magnetic field, we can find the magnitude of temperature and magnetic field: M=K PT K BH C L -K PH K BT Among them, K BH K represents the magnetic field sensitivity coefficient of the wavelength of light in the FBG. PH represents the magnetic field sensitivity coefficient of the FP cavity, K PT represents the temperature sensitivity coefficient of the FP cavity, K BT It represents the temperature sensitivity coefficient of the wavelength of light in the FBG.

8. A dual-parameter optical fiber sensor measurement method, characterized in that: The optical fiber temperature and magnetic field dual parameter sensor according to any one of claims 1 to 7 is implemented, comprising: an incident light L emitted by a light source im The incident light L is transmitted to the first port of the fiber coupler through the transmission fiber. in When transmitted to the single-mode optical fiber through the second port of the optical fiber coupler, a part of it is reflected by the FBG to obtain reflected light L1, and the reflected light L1 is received by the optical spectrum analyzer through the third port of the optical fiber coupler. in The other part of the transmitted light L2 reaches the FP cavity, and generates interference light L3 through the interface M1 and the interface M2. The interference light L3 returns through the FBG and is output. The final output light is composed of L1 and L3. Calculate the magnetic field sensitivity and temperature sensitivity of the light wavelength in the FP cavity, the temperature sensitivity and magnetic field sensitivity of the light wavelength in the FBG, calculate the correlation coefficient, and realize the synchronous dual parameter measurement of magnetic field and temperature.

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