A FP interferometric temperature-strain dual-parameter sensor and its preparation method

Abstract

The present invention relates to the field of sensor technology, and specifically to an F-P interferometric temperature-strain dual-parameter sensor and a preparation method thereof, comprising a hollow-core optical fiber, a first optical fiber, a second optical fiber, a first fixing portion, and a second fixing portion; the first optical fiber and the second optical fiber extend into the hollow-core optical fiber from both ends of the hollow-core optical fiber, respectively, and ultraviolet glue is provided between the first optical fiber and the hollow-core optical fiber, and between the second optical fiber and the hollow-core optical fiber; in the hollow-core optical fiber, a gap is provided between the first end face of the first optical fiber and the second end face of the second optical fiber; a first grid area is provided near the first end face in the first optical fiber; the first fixing portion and the second fixing portion are respectively fixed at both ends of the outer side of the hollow-core optical fiber. The present invention can simultaneously measure two parameters, temperature and strain, and uses the temperature measurement result to correct the F-P cavity deformation caused by temperature, thereby reducing the error caused by temperature change, and thus can achieve high-precision measurement of strain.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a FP interference type temperature-strain dual-parameter sensor and a preparation method thereof. Background Art

[0002] Since the strain caused by the growth of defects in pressure vessels is usually very small, the requirements for the skills of the inspectors and the accuracy of the equipment are also increasing. As the service life of pressure vessels increases, pressure vessels often encounter safety issues during service. In particular, the safety of pressure vessels that store some flammable, explosive, highly corrosive or toxic chemical raw materials during service has received more and more attention and attention.

[0003] When the pressure vessel is working, it is impossible to directly measure the damage from the inside. It is necessary to detect the deformation of the pressure vessel to obtain the morphological characteristics of the defect. The pressure or pressure inside the pressure vessel can only be detected by measuring the deformation of the pressure vessel. The FP (Fabry-Perot) interferometric optical fiber strain sensor has high sensitivity when measuring strain. However, the FP cavity is also easily affected by the ambient temperature, making the measurement inaccurate. Summary of the invention

[0004] In view of the above problems, the present invention provides an FP interference type temperature strain dual parameter sensor, comprising a hollow core optical fiber, a first optical fiber, a second optical fiber, a first fixing portion, and a second fixing portion; the first optical fiber and the second optical fiber extend into the hollow core optical fiber from both ends of the hollow core optical fiber respectively, and ultraviolet glue is provided between the first optical fiber and the hollow core optical fiber, and between the second optical fiber and the hollow core optical fiber; in the hollow core optical fiber, a gap is provided between the first end face of the first optical fiber and the second end face of the second optical fiber; a first grating area is provided in the first optical fiber near the first end face; the first fixing portion and the second fixing portion are respectively fixed at both ends of the outer side of the hollow core optical fiber.

[0005] Furthermore, the first optical fiber and the second optical fiber are single-mode optical fibers, which are used to concentrate the energy of the light field mainly in the middle of the FP cavity, so as to facilitate detection by the light detector.

[0006] Furthermore, the first fixing portion and the second fixing portion are fixed to the outside of the hollow-core optical fiber in a circumferential manner, so that the first fixing portion and the second fixing portion are more firmly fixed to the outside of the hollow-core optical fiber.

[0007] Furthermore, outside the first optical fiber, the UV glue is not arranged outside the first grid area, so that when an axial force is applied between the first fixing part and the second fixing part, the first grid area is not subjected to tension, that is, the first grid area is only affected by the ambient temperature.

[0008] Furthermore, a noble metal film is provided on the second end surface so as to form a stronger concentrated light field between the first end surface and the second end surface, which is convenient for detection by the light detector.

[0009] Furthermore, the thickness of the noble metal film is less than 20 nanometers.

[0010] Furthermore, the material of the noble metal film is gold.

[0011] Furthermore, a second grating region is provided in the second optical fiber near the second end face.

[0012] Furthermore, the central wavelength of the second gate region is not equal to the central wavelength of the first gate region.

[0013] The preparation method of the FP interferometric temperature-strain dual-parameter sensor comprises the following steps:

[0014] S1, removing a certain length of the coating layer of the end of the first optical fiber away from the first grid area and then welding it with the jumper;

[0015] S2, prepare a hollow-core optical fiber of appropriate length and wipe it clean with alcohol;

[0016] S3, after removing the coating layer from the other end of the first optical fiber, wipe it clean with alcohol;

[0017] S4, inserting another section of optical fiber into the hollow-core optical fiber from both ends of the hollow-core optical fiber successively to remove impurities with larger diameters inside the hollow-core optical fiber;

[0018] S5, cutting the first grid area with a fiber cutting machine, retaining a certain length of the first grid area, discharging and cleaning the end face, and then placing the first optical fiber in a fusion splicer to ensure that the first end face of the first optical fiber is flat;

[0019] S6, inserting the end of the first optical fiber having the first grating region into the hollow core optical fiber and fixing it with ultraviolet glue;

[0020] S7, cutting the second optical fiber with an optical fiber cutting machine, discharging and cleaning the end face, and then placing the second optical fiber in a fusion splicer to ensure that the end face of the second optical fiber is flat;

[0021] S8, inserting one end of the cut end face of the second optical fiber into the hollow-core optical fiber from the other end of the hollow-core optical fiber;

[0022] S9, adjusting the distance between the second end face of the second optical fiber and the first end face of the first optical fiber so that an FP cavity is formed between the first end face and the second end face.

[0023] Beneficial effects of the present invention: The present invention provides a FP interferometric temperature-strain dual-parameter sensor, comprising a hollow-core optical fiber, a first optical fiber, a second optical fiber, a first fixing portion, and a second fixing portion; the first optical fiber and the second optical fiber extend into the hollow-core optical fiber from both ends of the hollow-core optical fiber, respectively, and ultraviolet glue is provided between the first optical fiber and the hollow-core optical fiber, and between the second optical fiber and the hollow-core optical fiber; in the hollow-core optical fiber, a gap is provided between the first end face of the first optical fiber and the second end face of the second optical fiber; a first grating area is provided near the first end face in the first optical fiber; the first fixing portion and the second fixing portion are respectively fixed at both ends of the outer side of the hollow-core optical fiber. When in use, the first fixing portion and the second fixing portion are fixed on the outer surface of the pressure vessel, and the present invention can also be directly adhered to the vessel wall, and the first optical fiber is connected to a continuous spectrum light source and a light detector through an optical circulator. In the present invention, an FP cavity is formed between the first end face and the second end face to measure the axial stress or displacement between the first fixing portion and the second fixing portion, and the strain or displacement between the first fixing portion and the second fixing portion is determined by the resonant wavelength movement of the FP cavity. The first grating area is used to measure the temperature of the environment, specifically, the central wavelength of the reflected light is detected by the light detector, and the ambient temperature is determined by the central wavelength movement of the reflected light. That is to say, the present invention can measure both temperature and strain parameters at the same time, and use the temperature measurement result to correct the FP cavity deformation caused by temperature, thereby reducing the error caused by temperature change. Therefore, the present invention can achieve high-precision strain measurement and enhance the anti-interference ability of the sensor.

[0024] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a FP interferometric temperature-strain dual-parameter sensor.

[0026] Figure 2 This is a schematic diagram of another FP interference type temperature-strain dual-parameter sensor.

[0027] Figure 3 It is the sensor spectrum during temperature test.

[0028] Figure 4 is the central wavelength of the first grating region at different temperatures.

[0029] Figure 5 is the central wavelength of the second grating region at different temperatures.

[0030] Figure 6 is the resonance wavelength of the FP cavity at different temperatures.

[0031] Figure 7 It is the drift diagram of axial tensile strain spectrum.

[0032] Figure 8is the central wavelength of the first grating region at different temperatures.

[0033] Fig. 9 is the resonance wavelength of the FP cavity at different temperatures and strains.

[0034] In the figure: 1. hollow core optical fiber; 2. first optical fiber; 3. second optical fiber; 4. UV glue; 5. first end face; 6. second end face; 7. first grid area; 8. first fixing part; 9. second fixing part; 10. second grid area. DETAILED DESCRIPTION

[0035] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose, the specific implementation methods, structural features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and embodiments.

[0036] Example 1

[0037] The present invention provides a FP interferometric temperature-strain dual-parameter sensor, such as Figure 1 As shown, the sensor includes a hollow-core optical fiber 1, a first optical fiber 2, a second optical fiber 3, a first fixing portion 8, and a second fixing portion 9. The first optical fiber 2 and the second optical fiber 3 include a core and a cladding, or the first optical fiber 2 and the second optical fiber 3 include a core and a part of the cladding. The first optical fiber 2 and the second optical fiber 3 extend into the hollow-core optical fiber 1 from both ends of the hollow-core optical fiber 1, respectively. The first optical fiber 2 and the second optical fiber 3 can be single-mode optical fibers or multi-mode optical fibers. Preferably, the first optical fiber 2 and the second optical fiber 3 are single-mode optical fibers, which are used to concentrate the energy of the light field mainly in the middle of the FP cavity, so as to facilitate detection by the light detector. Ultraviolet glue 4 is provided between the first optical fiber 2 and the hollow-core optical fiber 1, and between the second optical fiber 2 and the hollow-core optical fiber 1; the ultraviolet glue 4 fixes the hollow-core optical fiber 1 to the outside of the first optical fiber 2 and the second optical fiber 3. In the hollow-core optical fiber 1, a gap is provided between the first end face 5 of the first optical fiber 2 and the second end face 6 of the second optical fiber 3; the distance between the first end face 5 and the second end face 6 is greater than 1 micron and less than 10 microns, and the gap forms an FP cavity. A first grating region 7, i.e., a Bragg grating, is provided in the first optical fiber 2 near the first end face 5; the reflectivity of the first grating region 7 is small so that more light can enter the gap between the first end face 5 and the second end face 6. The first fixing portion 8 and the second fixing portion 9 are respectively fixed at two ends of the outer side of the hollow core optical fiber 1. Preferably, the first fixing portion 8 and the second fixing portion 9 are fixed around the outer side of the hollow core optical fiber 1 so that the first fixing portion 8 and the second fixing portion 9 are more firmly fixed to the outer side of the hollow core optical fiber 1. In the hollow core optical fiber 1 and outside the first optical fiber 2, the ultraviolet glue 4 is not provided on the outer side of the first grating region 7, that is, the first grating region 7 is in a suspended state, so that when an axial force is applied between the first fixing portion 8 and the second fixing portion 9, the first grating region 7 is not subjected to a tensile force, that is, the first grating region 7 is only affected by the ambient temperature.

[0038] When in use, the first fixing part 8 and the second fixing part 9 are fixed on the outer surface of the pressure vessel, and the first optical fiber 2 is connected to the continuous spectrum light source and the optical detector through an optical circulator. In the present invention, an FP cavity is formed between the first end face 5 and the second end face 6 to measure the axial stress or displacement between the first fixing part 8 and the second fixing part 9, and the deformation or displacement between the first fixing part 8 and the second fixing part 9 is determined by the resonant wavelength movement of the FP cavity. The first grating area 7 is used to measure the temperature of the environment, specifically, the central wavelength of the reflected light is detected by the optical detector. When the ambient temperature changes, the central wavelength of the first grating area 7 changes under the influence of the optical fiber thermo-optic effect, elastic-optic effect and thermal expansion effect, and the central wavelength of the first grating area 7 moves, and the temperature is determined by the movement of the central wavelength of the first grating area 7; in the experiment, the ambient temperature is determined by the resonant wavelength movement of the reflected light. That is to say, the present invention can simultaneously measure the two parameters of temperature and strain, and use the temperature measurement result to correct the FP cavity deformation caused by temperature, thereby reducing the error caused by temperature change. Therefore, the present invention can achieve high-precision measurement of strain and enhance the anti-interference ability of the sensor.

[0039] In addition, in the present invention, the first fixing part 8 and the second fixing part 9 can also be respectively fixed on the first optical fiber 2 and the second optical fiber 3 outside the hollow core optical fiber 1. When the first fixing part 8 and the second fixing part 9 apply tension, no stress will be applied to the first grating area 7. Therefore, the technical effect of the present invention can also be met.

[0040] Preferably, the first end face 5 and the second end face 6 are concave surfaces, so that the first end face 5 and the second end face 6 concentrate more light energy at the center of the FP cavity, thereby increasing the amount of light reflection and facilitating detection by the light detector.

[0041] In the present invention, the first grating region 7 is a fiber Bragg grating, and the wavelength response condition of the fiber Bragg grating is:

[0042] λ B =2n eff Λ,

[0043] In the formula, λ B is the resonant wavelength, n eff is the effective refractive index, and Λ is the grating period.

[0044] After fully differentiating both sides of the above equation, we can get

[0045] dλ B =2n eff dΛ+2Λdn eff .

[0046] In the present invention, the first gate region 7 is in a freely suspended state and is therefore only affected by temperature.

[0047] By

[0048] and

[0049] Available

[0050]

[0051] In the present invention,

[0052] Then the central wavelength shift of the first grid region 7 has the following relationship:

[0053]

[0054] Where ξ is the thermo-optic coefficient and α is the thermal expansion coefficient. Changes in the thermo-optic coefficient will cause changes in the refractive index; changes in the thermal expansion coefficient will cause changes in the grating period.

[0055] Therefore, the temperature sensitivity of the first gate region 7 is

[0056]

[0057] In the present invention, when the temperature changes, the length of the FP cavity will also change. During the temperature test, the temperature sensitivity of the FP cavity can be obtained by simply tracking the wavelength value of a certain trough. The length change of the FP cavity caused by the temperature is corrected by measuring the temperature of the first gate region 7, that is, the FP cavity is temperature compensated.

[0058] In terms of strain measurement of FP cavity:

[0059] The transmission spectrum of a mode interferometer is usually composed of multiple different modes superimposed, and the intensity can be written as

[0060]

[0061] Where I is the light intensity of the guided light wave, n is the effective refractive index, L is the interference length, λ is the wavelength of the guided light wave in the optical fiber, and the subscripts i and j represent the relevant parameters of the i-th and j-th order mode light waves respectively.

[0062] In the present invention, since the first grid area 7 is in a suspended state, the first grid area 7 is not affected by stress. At this time, the FP cavity produces tensile deformation as the hollow-core optical fiber 1 changes under the action of external force, and the cavity length L of the FP cavity will change. By monitoring the change of L, the corresponding variable can be measured. The strain calculation formula of the FP cavity is: Where Δl is the change in the length of the FP cavity, L e is the effective working length of the hollow core optical fiber.

[0063] When incident light enters from one side of the weakly reflective first gate region 7, part of the light is reflected at the first gate region 7, and most of the light is transmitted through the first gate region 7 and enters the FP cavity due to the weak reflective ability of the first gate region 7.

[0064] Example 2

[0065] On the basis of Example 1, Figure 2 As shown, a second grating area 10 is provided in the second optical fiber 6 near the second end face 6, that is, the second end face 6 is formed by cutting the second grating area 10. The central wavelength of the second grating area 10 is not equal to the central wavelength of the first grating area 7. In this way, two reflection peaks will appear in the reflection spectrum measured by the light detector, and the temperature of the environment can be determined more accurately through the wavelength difference of the two reflection peaks or the respective reflection peak positions. In addition, since the working environment of the pressure vessel is relatively complex, the sensor may be damaged by greater interference from the external environment or improper human operation during operation. If one of the Bragg gratings is damaged and cannot normally feedback to the change in ambient temperature, the damage to the sensor can be found by comparison with another Bragg grating and replaced in time. Of course, the second grating area 10 set in this embodiment can also be used for temporary measurement.

[0066] Furthermore, inside the hollow-core optical fiber 1 and outside the second optical fiber 3, the UV glue 4 is not arranged on the outside of the second grating area 10, so that when an axial force is applied between the first fixing part 8 and the second fixing part 9, the second grating area 10 is not subjected to tension, that is, the second grating area 10 is only affected by the ambient temperature.

[0067] In order to test the performance of the FP interferometric temperature-strain dual-parameter sensor designed in this embodiment, the sensor was placed in the center of the heating platform to test its temperature response characteristics. The temperature was gradually increased from 20 degrees Celsius to 60 degrees Celsius, and the spectral data was recorded every 5 degrees Celsius, and the temperature error was kept within 0.2 degrees Celsius.

[0068] Figure 3 It is a spectrum diagram at different temperatures. It can be seen from the figure that with the increase of temperature, the central wavelengths of the first gate region 7 and the second gate region 10 have a slight red shift, and the resonance peak of the FP cavity has an obvious red shift phenomenon. This shows that temperature has a great influence on the FP cavity.

[0069] The data of the first gate region 7, the second gate region 10, and the central wavelength or resonant wavelength of the FP cavity are extracted, respectively, as shown in FIG. Figure 4 , Figure 5 , Figure 6 As shown. Figure 4 It can be concluded that the temperature sensitivity K of the first gate region 7 is T1(FBG)is 8.49pm / ℃; Figure 5 The temperature sensitivity K of the second gate region 10 can be obtained as T2(FBG) is 8.47pm / ℃; Figure 6 The temperature sensitivity K of the FP cavity can be obtained T(FP) It is 193pm / ℃.

[0070] When performing strain testing, use UV glue to fix the two ends of the sensor on the translation table, so that the distance between the two fixed points is 200mm, and the effective length of the hollow-core optical fiber 1 is about 50mm. Before the stress test begins, let the sensor be in a state without axial stress. The accuracy of the translation table is 0.01mm, the distance of each movement is 0.01mm, the total displacement is 0.1mm, and the strain applied to the sensor is 200. Temperature strain tests are carried out at 20℃, 40℃, and 60℃ respectively.

[0071] The strain test results at 20℃ are as follows Figure 7 .from Figure 7 It can be found that the central wavelengths of the first grating region 7 and the second grating region 10 have not changed, but the trough peak of the FP cavity has an obvious red shift phenomenon. This is because the first grating region 7 and the second grating region 10 are in a suspended state in the hollow core optical fiber 1, so they are not affected by the axial tensile stress. When the axial stress is applied, the length of the FP cavity is increased, and the trough wavelength of the FP microcavity is red shifted accordingly. When the temperature increases, according to the results of the temperature test, the central wavelengths of the first grating region 7 and the second grating region 10 and the trough wavelength of the FP cavity will be red shifted accordingly.

[0072] like Figure 8 As shown in FIG. 1 , when the temperature rises, the peak movement of the first gate region 7 is almost consistent with the result of the temperature test. Fig. 9 As shown in the figure, under different temperature conditions, the strain curves of the FP cavity show good linearity, with a linear index of more than 98% and are parallel to each other. The strain sensitivity of the FP cavity is calculated to be K ε(FP) It is 7.79pm / με.

[0073] In the process of online monitoring of pressure vessels, usually only the stress or strain parameter changes need to be obtained. However, the external temperature change will cause the material properties to change, which will in turn affect the measurement results of strain or stress. Let Δε be the strain change and ΔT be the temperature change.

[0074]

[0075] In the formula, Δλ FBG and Δλ FP are the wavelength changes of FBG and FP microcavities respectively. ε(FBG) is 0.

[0076] According to the experimental results, assuming that in a certain test, the measured Δλ FBG is 0.1698nm, Δλ FP is 8.959nm. Before the sensor is temperature-corrected, Δε0 is 1150.06με. According to the experimental results above, ΔT is 20℃, and then Δε is 654.56με. Compared with Δε0, Δε has been greatly improved. Therefore, the temperature-strain dual-parameter FP interferometric sensor designed in this paper can effectively reduce the strain error caused by temperature, realize temperature compensation in the strain measurement process, and improve the strain measurement accuracy.

[0077] Example 3

[0078] On the basis of embodiment 1, a noble metal film is provided on the second end face 6, and the thickness of the noble metal film is less than 20 nanometers. The material of the noble metal film is gold, so as to form a stronger focusing electric field between the first end face 5 and the second end face 6, which is convenient for the second photodetector to detect.

[0079] Furthermore, the noble metal film is thin in the middle and thick at the edge, so that the energy in the FP cavity is concentrated at the center of the FP cavity, so that more energy can be coupled into the second optical fiber 3 to facilitate detection by the second optical detector.

[0080] Example 4

[0081] The present invention provides a method for preparing a FP interferometric temperature-strain dual-parameter sensor, the preparation process comprising the following steps:

[0082] S1, removing a certain length of the coating layer of the end of the first optical fiber 2 away from the first grating area 7 and then welding it with the jumper;

[0083] S2, prepare a hollow core optical fiber 1 of suitable length and wipe it clean with alcohol;

[0084] S3, after removing the coating layer from the other end of the first optical fiber 2, wipe it clean with alcohol;

[0085] S4, inserting another section of optical fiber into the hollow-core optical fiber 1 from both ends of the hollow-core optical fiber 1 successively to remove impurities with larger diameters inside the hollow-core optical fiber 1;

[0086] S5, cutting the first grid area 7 with a fiber cutting machine, retaining a certain length of the first grid area 7, and after discharge cleaning, placing it in a fusion splicer to ensure that the first end face 5 of the first optical fiber 2 is flat;

[0087] S6, inserting the end of the first optical fiber 2 having the first grating region 7 into the hollow core optical fiber 1 and fixing it with ultraviolet glue 4;

[0088] S7, cutting the second optical fiber 3 with an optical fiber cutter, and after discharge cleaning, placing the second optical fiber 3 in a fusion splicer to ensure that the end surface of the second optical fiber 3 is flat;

[0089] S8, inserting one end of the cut end face of the second optical fiber 3 into the hollow-core optical fiber 1 from the other end of the hollow-core optical fiber 1;

[0090] S9, adjusting the distance between the second end face 6 of the second optical fiber 3 and the first end face 5 of the first optical fiber 2 so that an FP cavity is formed between the first end face 5 and the second end face 6;

[0091] S10, using ultraviolet glue 4 to fix and connect the second optical fiber 3 and the hollow core optical fiber 1.

[0092] When preparing the device in Example 3, in S7, the second grating region 10 in the second optical fiber 3 is cut with an optical fiber cutter to form a grating region of a certain length. After discharge cleaning, the optical fiber end face is determined to be flat in a fusion splicer; in S8, one end of the second grating region 10 is inserted into the hollow core optical fiber 1.

[0093] In S9, when the length of the FP cavity is adjusted, the adjustment is ended when the Bragg grating reflection peak and the FP cavity interference pattern appear simultaneously in the spectrometers in the first photodetector and the second photodetector.

[0094] Finally, it should be noted that, in the present invention, only the first photodetector may be used to determine the reflection peaks of the first grating region 7 and the second grating region 10 and the interference pattern of the FP cavity.

[0095] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A FP interferometric temperature-strain dual-parameter sensor, characterized in that: It comprises a hollow-core optical fiber, a first optical fiber, a second optical fiber, a first fixing part, and a second fixing part; the first optical fiber and the second optical fiber extend into the hollow-core optical fiber from two ends of the hollow-core optical fiber respectively, and ultraviolet glue is provided between the first optical fiber and the hollow-core optical fiber, and between the second optical fiber and the hollow-core optical fiber; in the hollow-core optical fiber, a gap is provided between the first end face of the first optical fiber and the second end face of the second optical fiber; a first grating area is provided in the first optical fiber near the first end face, and outside the first optical fiber, the ultraviolet glue is not provided on the outside of the first grating area, and the first grating area is suspended; the first fixing part and the second fixing part are respectively fixed at two ends of the outside of the hollow-core optical fiber; when in use, the first fixing part and the second fixing part are fixed on the outer surface of the pressure vessel; the first optical fiber and the second optical fiber are single-mode optical fibers.

2. The FP interferometric temperature-strain dual-parameter sensor according to claim 1, characterized in that: The first fixing portion and the second fixing portion are circumferentially fixed on the outside of the hollow core optical fiber.

3. The FP interferometric temperature-strain dual-parameter sensor according to claim 1 or 2, characterized in that: A noble metal film is disposed on the second end surface.

4. The FP interferometric temperature-strain dual-parameter sensor according to claim 3, characterized in that: The thickness of the noble metal film is less than 20 nanometers.

5. The FP interferometric temperature-strain dual-parameter sensor according to claim 4, characterized in that: The material of the noble metal film is gold.

6. The FP interferometric temperature-strain dual-parameter sensor according to claim 1 or 2, characterized in that: A second grating region is provided in the second optical fiber near the second end face.

7. The FP interferometric temperature-strain dual-parameter sensor according to claim 6, characterized in that: The central wavelength of the second gate region is not equal to the central wavelength of the first gate region.

8. The method for preparing the FP interferometric temperature-strain dual-parameter sensor according to claim 1, characterized in that: The preparation method comprises the following steps: S1, removing a certain length of the coating layer of the end of the first optical fiber away from the first grid area and then welding it with the jumper; S2, prepare a suitable length of the hollow core optical fiber and wipe it clean with alcohol; S3, removing the coating layer from the other end of the first optical fiber and wiping it clean with alcohol; S4, inserting another section of optical fiber into the hollow-core optical fiber from both ends of the hollow-core optical fiber successively to remove impurities with larger diameters inside the hollow-core optical fiber; S5, cutting the first grid area with a fiber cutting machine, retaining a certain length of the first grid area, discharging and cleaning the end face, and then placing the first optical fiber in a fusion splicer to ensure that the first end face of the first optical fiber is flat; S6, inserting the end of the first optical fiber having the first grating region into the hollow core optical fiber and fixing it with ultraviolet glue; S7, cutting the second optical fiber with an optical fiber cutter, cleaning the end face with discharge, and placing the second optical fiber in a fusion splicer to ensure that the end face of the second optical fiber is flat; S8, inserting one end of the cut end face of the second optical fiber into the hollow-core optical fiber from the other end of the hollow-core optical fiber; S9, adjusting the distance between the second end face of the second optical fiber and the first end face of the first optical fiber so that an FP cavity is formed between the first end face and the second end face.

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