High-sensitivity Mach-Zehnder strain sensor and manufacturing and using method thereof

Abstract

The invention belongs to the field of optical fiber Mach-Zehnder interference sensors, and particularly relates to a high-sensitivity Mach-Zehnder strain sensor and a manufacturing and using method thereof. Comprising a light injection area, a circular ring sensing area and a light receiving area which are sequentially arranged on an optical fiber; the circular ring sensing area is composed of a double-spiral-shaped regulation and control area and a semi-circular ring sensing area, and the optical fiber of the circular ring sensing area part is not provided with a coating layer. When axial strain is applied to the sensor, the shape of the circular ring area is gradually changed into an oval shape from a round shape, the positions of a beam splitting point and a beam combining point on the semi-circular ring sensing area are changed, the length of the sensing area is changed, interference troughs move, and strain sensing is achieved. The length of a sensing area in the strain process is greatly changed, and the drift distance of an interference trough is greatly moved, so that strain sensitization can be realized. The Mach-Zehnder strain sensor solves the problems that an existing Mach-Zehnder strain sensor is limited by the change range with the small core cladding refractive index difference, and the strain sensitivity cannot be further improved.

Description

Technical Field

[0001] The present invention belongs to the field of fiber optic Mach-Zehnder interferometric sensors, and particularly relates to a highly sensitive Mach-Zehnder strain sensor and its manufacturing and usage methods. Background Art

[0002] A fiber optic Mach-Zehnder (MZI) strain sensor is a strain measurement device based on the principle of a fiber optic Mach-Zehnder interferometer. It utilizes the interference effect of light in the optical fiber to detect and measure strain, and is widely used in fields such as civil engineering, mechanical structure health monitoring, aerospace, and biomedicine.

[0003] In strain measurement, strain sensitivity is an important indicator for evaluating a fiber optic Mach-Zehnder (MZI) strain sensor. Currently, MZI strain sensors mainly rely on the response of the refractive index difference between the core and the cladding to strain. However, limited by the small change range of the core-cladding refractive index difference, its strain sensitivity cannot be further improved. Therefore, it is necessary to explore the principle and design the structure to achieve a highly sensitive MZI strain sensor.

[0004] During the strain measurement process, the greater the movement of the interference valley of the fiber optic interference strain sensor, the higher the strain sensitivity. The movement of the interference valley is jointly determined by four parameters: the length of the sensing region, the effective refractive index difference between the core mode and the cladding mode, the change in the effective refractive index difference between the core mode and the cladding mode during the strain process, and the change in the length of the sensing region during the strain process. Among them, after the fiber optic MZI strain sensor is fabricated, the two parameters of the length of the sensing region and the effective refractive index difference between the core and cladding modes are already determined. Therefore, increasing the change in the effective refractive index difference between the core and cladding modes during the strain process or increasing the change in the length of the sensing region during the strain process can cause the interference valley to move, thereby achieving strain sensing. Currently, the mainstream method for improving the strain sensitivity of MZI strain sensors is to increase the change in the effective refractive index difference between the core mode and the cladding mode during the strain process, which is often achieved by exciting higher-order cladding modes. For example, Dong et al. tapered a hollow fiber to excite higher-order cladding modes, and the strain sensitivity was increased to -2.6 pm / με (DONG L, GANG T, BIAN C, et al. A high sensitivity opticalfiber strain sensor based on hollow core tapering[J]. Optical FiberTechnology, 2020, 56.). Sun et al. excited higher-order cladding modes by twisting the optical fiber, and the strain sensitivity reached -42.5 pm / με (SUN Y, LIU D, LU P, et al. High sensitivity optical fiber strain sensorusing twisted multimode fiber based on SMS structure[J]. OpticsCommunications, 2017, 405:416-20.). Liu et al. used a single-mode-multimode-thin-core tapered misaligned-multimode-single-mode structure, tapered and misaligned the splicing of the thin-core fiber, making it easier for the core light to leak into the cladding for transmission and exciting higher-order cladding modes, and the strain sensitivity was -45 pm / με (LIU C, ZHANG M, ZHANG H, et al. Tapered-open-cavity-based in-line Mach–Zehnder interferometer for highly sensitive axial-strainmeasurement[J]. Optics Express, 2022, 30(4)). However, the method of changing the change in the effective refractive index difference between the core mode and the cladding mode is limited by the photoelastic coefficients of the core mode and the cladding mode, and the sensitization effect is limited.

[0005] In summary, the current fiber optic MZI strain-sensitization method is limited by the relatively small change range of the core-cladding refractive index difference, unable to break through the elasto-optic coefficient limit, with poor strain-sensitization effect and unable to achieve high-sensitivity strain measurement. Summary of the Invention

[0006] The main object of the present invention is to propose a high-sensitivity Mach-Zehnder strain sensor and its manufacturing and usage method, to solve the problem that the current MZI strain sensor is limited by the relatively small change range of the core-cladding refractive index difference and its strain sensitivity cannot be further improved.

[0007] To solve the above problems, the present application provides a high-sensitivity Mach-Zehnder strain sensor, including a light injection area, a circular ring sensing area, and a light receiving area sequentially arranged on a single optical fiber, where the light injection area, the circular ring sensing area, and the light receiving area are located on one continuous optical fiber of the same type; the circular ring sensing area is composed of an upper semi-circular ring sensing area and a lower double-helix shape regulation area, and the optical fiber forming the circular ring sensing area has no coating layer; the diameter of the circular ring sensing area is 1.8 cm - 2.2 cm; the curvature maximum points on the left and right sides of the semi-circular ring sensing area are the beam splitting point and the beam combining point, and the distance between the beam splitting point and the beam combining point is the length of the sensing area; the winding times of the double-helix shape regulation area are 2 - 4 times, where the winding times are proportional to the change amount of the sensing area length, and the change amount of the sensing area length is proportional to the strain sensitivity, and the strain sensitivity of the sensor is adjusted by selecting the winding times.

[0008] The diameter of the circular ring sensing area is 1.8 cm - 2.2 cm. When the diameter is greater than 2.2 cm, the curvature of the beam splitting point and the beam combining point is too small, and the light beam cannot be coupled from the core into the cladding for transmission; when the diameter is less than 1.8 cm, the curvature of the beam splitting point and the beam combining point is too large, and the optical fiber is easily broken during the strain process.

[0009] The winding times of the spiral shape regulation area are 2 - 4 times. When the winding times are 1 time, when the circular ring structure is subjected to strain modulation, only an equal-proportion change in the size of the circular ring occurs, and no deformation occurs, that is, the change amount of the sensing area length is a constant value and a strain sensing of the sensing area length modulation type cannot be achieved; when the winding times are greater than 4 times, the curvature of the beam splitting point and the beam combining point is too large, and the optical fiber is easily broken during the strain process. The more the winding times, the greater the circular ring deformation amount during the strain process, that is, the greater the position change of the beam splitting point and the beam combining point, the greater the change amount of the sensing area length, and the higher the strain sensitivity of the sensor. The strain sensitivity of the sensor can be adjusted by adjusting the winding times in this area.

[0010] According to the double-beam interference principle of the Mach-Zehnder interferometer (MZI), when the sensor is subjected to axial strain, the drift amount of the wavelength characterizes the magnitude of the strain sensitivity. Therefore, the strain sensitivity S is deduced as shown in formula (1):

[0011]

[0012] Among them, n co represents the core refractive index of a single-mode fiber (SMF), a represents the core diameter of the SMF, and L is the length of the sensing region. Among them, when the optical fiber is only affected by axial strain modulation, the effective refractive index is affected by the elasto-optic effect, the diameter is affected by the Poisson effect, and the length of the sensing region is affected by the strain effect, and can be expressed as shown in formula (2):

[0013]

[0014] Among them, p 11 and p 12 are elasto-optic coefficients, v is the Poisson coefficient of the optical fiber, and p e is the effective elasto-optic coefficient. Therefore, formula (1) can be written as shown in formula (3):

[0015]

[0016] Among them, for a single-mode fiber, v = 0.17, p e = 0.22. Therefore, it can be known that the strain sensitivity is jointly affected by the elasto-optic effect, the Poisson effect, and the strain effect. Among them, the coefficient of the strain effect is 1, while the coefficients of the elasto-optic effect and the Poisson effect are both decimals less than 1. Therefore, it can be known that the strain effect has the greatest influence on the wavelength drift. However, in the current strain-sensitization research, the change amount (ΔL) of the sensing region length in the strain effect (ΔL / L = ε) is difficult to change significantly. Therefore, strain sensitization is achieved by changing the change amount of the effective refractive index difference. If the change amount of the sensing region length can be adjusted, strain sensitization can be achieved.

[0017] When the sensor is subjected to axial strain, due to the existence of the double-helix shape control region, the shape of the circular ring sensing region gradually changes from circular to elliptical, the positions of the maximum curvature on the left and right sides of the semi-circular ring sensing region change, and the positions of the beam splitting point and the beam combining point change accordingly, and the length of the sensing region increases. The greater the change amount of the sensing region length caused by the strain, the higher the strain sensitivity.

[0018] As a preferred solution, the optical fiber is a single-mode fiber with the core centered.

[0019] As a preferred solution, the cladding diameter of the optical fiber is 125 μm, the core diameter is 9 μm, and the coating diameter is 250 μm.

[0020] Another object of the present invention is to provide a manufacturing and use method of a highly sensitive Mach-Zehnder strain sensor.

[0021] As a preferred solution, the manufacturing method of the above-mentioned highly sensitive Mach-Zehnder strain sensor is as follows:

[0022] S1: Take a 1-meter-long single-mode optical fiber, use a Miller pliers to strip the coating layer with a length of 10 cm in the middle of the single-mode optical fiber, and wipe and clean it with a non-woven fabric dipped in anhydrous ethanol. Wind the middle section of the optical fiber counterclockwise for one circle so that the two ends of the optical fiber cross and overlap to form a circular ring shape with a middle diameter of 5 cm, and the optical fiber area with the coating layer stripped is located within the large circular ring area, with the light injection area at the left end below and the light receiving area at the right end above.

[0023] S2: Pass the light receiving area at the right end from the inside of the circular ring to the outside, and make the light injection area and the light receiving area on the same axis and the two ends facing in opposite directions.

[0024] S3: Pass the light receiving area from the inside of the circular ring to the outside, and repeat 2 to 4 times to form a circular ring structure with a double-helix-shaped regulation area.

[0025] S4: Apply uniform tensile force to both the left and right ends to shrink the circular ring structure and control its diameter to be 1.8 cm - 2.2 cm.

[0026] S5: Quickly heat the double-helix-shaped regulation area with the outer flame of an alcohol lamp to complete the production of the sensor.

[0027] As a preferred solution, the usage method of the above-mentioned highly sensitive Mach-Zehnder strain sensor is as follows: The light receiving area at the right end of the sensor is connected to a spectrometer, and the light injection area at the left end is connected to a light source. Clamp both ends of the sensor in the left and right displacement stage fixtures, and ensure that the optical fiber is in a straightened state. When controlling the left and right displacement stages to move through a strain control device and applying axial strain to both ends of the sensor, due to the existence of the double-helix-shaped regulation area, the shape of the circular ring sensing area gradually changes from a circle to an ellipse, and the positions of the beam splitting point and the beam combining point on the semi-circular ring sensing area change, resulting in a change in the length of the sensing area, and the output spectral interference wavelength changes accordingly. Record the interference wavelengths in the spectrometer under each strain, and demodulate the actual strain magnitude based on the interference wavelengths.

[0028] As a preferred solution, the performance adjustment method of the above-mentioned highly sensitive Mach-Zehnder strain sensor is as follows: The diameter of the circular ring sensing area of the sensor is 1.8 cm - 2.2 cm. By selecting different diameters, the initial shape of the circular ring structure is adjusted, and then the initial positions of the beam splitting point and the beam combining point are adjusted; The number of windings of the double-helix-shaped regulation area of the sensor is 2 to 4 times. By selecting different numbers of windings, the deformation degree of the circular ring structure during the strain process is adjusted, and then the length of the sensing area is adjusted, thereby adjusting the strain sensitivity of the sensor.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. The Mach-Zehnder strain sensor fabricated in this application realizes a method of fabricating beam splitting points and beam combining points without using fiber fusion or changing the internal structure of the optical fiber, enhancing the mechanical strength of the sensor.

[0031] 2. The Mach-Zehnder strain sensor fabricated in this application can change the positions of the beam splitting point and the beam combining point by changing the shape of the sensor, and a method for significantly changing the length of the sensing region is proposed, realizing high-sensitivity strain detection of the Mach-Zehnder strain sensor.

[0032] 3. For the Mach-Zehnder strain sensor fabricated in this application, by adjusting the number of winding turns in the double-helix shape control region, the relationship between the length of the sensing region and the strain sensitivity is established. By adjusting the number of winding turns, the degree of change in the structural shape during the strain process can be changed, the positions of the beam splitting point and the beam combining point can be changed, the change amount of the length of the sensing region can be changed, and thus the strain sensitivity can be changed, realizing adjustable sensitivity of the Mach-Zehnder strain sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the objectives, technical solutions and beneficial effects of the present invention clearer, the following drawings are provided for description of the present invention:

[0034] Figure 1 Schematic diagram of a high-sensitivity Mach-Zehnder strain sensor of the present invention;

[0035] Figure 2 Schematic diagram of the strain sensing device;

[0036] Figure 3 Schematic diagram of the deformation of the circular ring structure during the strain process;

[0037] Figure 4 Schematic diagram of the deformation of the circular ring structure before and after applying strain;

[0038] Figure 5 Diagram of the interference wavelength drift of the sensor under different axial strains;

[0039] Figure 6 Diagram of the strain detection data of the circular ring structure;

[0040] Figure 7 Diagram of the position of the beam splitting point on the right side of the circular ring structure under different strain actions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention schematically, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

[0042] Among them, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams rather than physical diagrams, and should not be construed as a limitation to the present invention; for better illustration of the embodiments of the present invention, some components in the accompanying drawings may be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0043] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] Next, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0045] The present invention can be implemented in the following manner:

[0046] The reference numerals in the accompanying drawings of the specification include: light injection area 1, circular ring sensing area 2, semi-circular ring sensing area 2-1, double helix shape regulation area 2-2, and light collection area 3.

[0047] As Figure 1 shown, this embodiment provides a highly sensitive Mach-Zehnder strain sensor, which includes a light injection area 1, a circular ring sensing area 2, and a light collection area 3 sequentially arranged on the optical fiber. Among them, the light injection area, the circular ring sensing area, and the light collection area are located on the same continuous optical fiber. The diameter of the optical fiber coating layer is 250 μm, the diameter of the cladding is 125 μm, and the diameter of the core is 9 μm. A single-mode optical fiber with the core centered is used; the circular ring sensing area 2 is composed of an upper semi-circular ring sensing area 2-1 and a lower double helix shape regulation area 2-2.

[0048] Among them, the diameter of the circular ring sensing area 2 is 1.8 cm - 2.2 cm, and preferably 1.8 cm in this embodiment; there is no coating layer on the outer side of the optical fiber forming the circular ring sensing area 2. When the light in the core passes through the beam splitting point of the semi-circular ring sensing area 2-1, due to the bending of the optical fiber in the upper semi-circular ring sensing area 2-1, the light is easily coupled into the cladding for transmission, forming an interference between the core mode and the cladding mode.

[0049] The number of turns of the double - helix - shaped regulation region 2 - 2 is 2 - 4 times, preferably 4 times in this embodiment. During the strain process, the degree of deformation of the sensor increases with the increase in the number of turns. The strain sensitivity of the sensor can be adjusted by changing the number of turns. The change in the length of the sensing region increases with the increase in the number of turns, and the strain sensitivity of the sensor increases with the increase in the number of turns.

[0050] When the shape of the circular - ring sensing region 2 changes, it will cause the positions of the points with the maximum curvature at both ends of the circular - ring structure to move to the left and right sides respectively. The positions of the beam - splitting point and the beam - combining point of the optical path change symmetrically. The length of the sensing region of the red segment increases, and the interference trough redshifts, realizing strain sensing. The change in the length of the sensor region is as Figure 4 shown. Figure 4 (a) is a schematic diagram of the shape of the circular - ring structure before applying strain, Figure 4 (b) is a schematic diagram of the shape of the circular - ring structure after applying strain. Figure 4(c) is a micrograph of the circular - ring structure before applying strain, Figure 4 (d) is a micrograph of the circular - ring structure after applying strain.

[0051] In this scheme, to verify the influence of the curvature change of the fiber - optic circular - ring structure under strain on the position of the beam - splitting point, the Rsoft software is used to simulate the situation of the position of the beam - splitting point at the right end of the circular - ring structure under different strains. The results are as Figure 7 shown. The simulation parameters are as follows: The cladding diameter of the single - mode fiber is 125 μm, and the refractive index is 1.446; the core diameter is 9 μm, and the refractive index is 1.455. When 0 με is applied, the curvature of the circular - ring structure is 3.3 cm -1 , and the position of the beam - splitting point is as Figure 7 (a) shown by the white dashed - line circle; when 200 με is applied, the curvature of the circular - ring structure is 4.0 cm -1 , and the position of the beam - splitting point is as Figure 7 (b) shown by the white dashed - line circle; when 400 με is applied, the curvature of the circular - ring structure is 4.5 cm -1 , and the position of the beam - splitting point is as Figure 7 (c) shown by the white dashed - line circle; it can be seen that with the increase in strain, the curvature of the circular - ring structure increases, and the position of the beam - splitting point at the right end of the circular - ring structure gradually moves to the right. Due to the symmetry of the structure, the beam - combining point at the left end of the circular - ring structure will also move to the left, increasing the length of the sensing region.

[0052] The specific manufacturing steps of the above - mentioned highly sensitive Mach - Zehnder strain sensor are as follows:

[0053] S1: Take a 1m long single-mode optical fiber, use a Miller pliers to strip the coating layer with a length of 10cm in the middle of the single-mode optical fiber, wipe and clean it with a non-woven fabric dipped in anhydrous ethanol, wind the middle section of the optical fiber counterclockwise for one circle, so that the two ends of the optical fiber cross and overlap to form a large ring shape with a diameter of 5cm, and the optical fiber area with the coating layer stripped is located within the large ring area, the light injection area at the left end is at the bottom, and the light receiving area at the right end is at the top.

[0054] S2: Pass the light receiving area at the right end from the inside to the outside of the ring, and make the light injection area and the light receiving area on the same axis and the two ends face in opposite directions.

[0055] S3: Pass the light receiving area from the inside to the outside of the ring, and repeat 4 times to form a ring structure with a double helix-shaped regulation area.

[0056] S4: Apply tensile forces evenly to the left and right ends to shrink the ring structure and control its diameter to 1.8cm.

[0057] S5: Quickly heat the double helix-shaped regulation area with the outer flame of an alcohol lamp to complete the production of the sensor.

[0058] As Figure 2 and Figure 3 shown, the usage method of the above high-sensitivity Mach-Zehnder strain sensor is as follows: The strain detection device is as Figure 2 shown. The light injection area 1 at the left end of the sensor is connected to the light source, and the light receiving area 3 at the right end is connected to the spectrometer. Clamp the two ends of the sensor in the left and right displacement stage jigs, and ensure that the optical fiber is in a straight state. By controlling the movement of the left and right displacement stages through the strain control device, when axial strain is applied to the two ends of the sensor, due to the existence of the double helix-shaped regulation area 2-2, the shape of the ring sensing area 2 changes from a circle as Figure 3 (a) gradually becomes an ellipse as Figure 3 (b). The splitting point and the combining point positions on the semi-ring sensing area 2-1 move downward to the right and downward to the left respectively, making the length of the sensing area longer, and the interference wavelength of its output spectrum changes accordingly. Record the interference wavelength in the spectrometer under each strain, and demodulate the actual strain magnitude according to the interference wavelength.

[0059] As Figure 5 shown, when the winding times of the double helix-shaped regulation area 2-2 is 4 times and the diameter of the ring sensing area 2 is 1.8cm, the specific usage method of the above high-sensitivity Mach-Zehnder strain sensor is as follows: The applied axial strain increases from 0με to 400με, and data is recorded every 100με. The interference wavelength drift of the sensor is as Figure 5 shown. As the strain increases, its interference wavelength undergoes regular red shift, as Figure 6 shown. Perform linear fitting on the interference wavelength and the applied strain, and the calculated strain sensitivity is 91.55pm / με.

Claims

1. A highly sensitive Mach-Zehnder strain sensor, characterized in that: It includes a light injection area, a circular sensing area and a light receiving area which are sequentially arranged on a single optical fiber; the circular sensing area is composed of an upper semi-circular sensing area and a lower double helix shape control area, and the optical fiber forming the circular sensing area has no coating layer; the diameter of the circular sensing area is 1.8cm-2.2cm; the points with the maximum curvature on the left and right sides of the semi-circular sensing area are the beam splitting point and the beam combining point, and the distance between the beam splitting point and the beam combining point is the sensing area length; the number of windings of the double helix shape control area is 2-4 times, wherein the number of windings is proportional to the change in the length of the sensing area, and the change in the length of the sensing area is proportional to the strain sensitivity, and the strain sensitivity of the sensor is adjusted by selecting the number of windings.

2. The highly sensitive Mach-Zehnder strain sensor based on a ring structure according to claim 1, characterized in that: The optical fiber is a single-mode optical fiber with a central core.

3. The highly sensitive Mach-Zehnder strain sensor based on a ring structure according to claim 2, characterized in that: The cladding diameter of the optical fiber is 125 μm, the core diameter is 9 μm, and the coating diameter is 250 μm.

4. A method for manufacturing the sensor as claimed in claim 1, characterized in that: S1: Take a 1m long single-mode optical fiber, use Miller pliers to strip off the coating layer of the middle length of 10cm of the single-mode optical fiber, and wipe it clean with a non-woven cloth soaked in anhydrous ethanol, and wind the middle section of the optical fiber counterclockwise so that the two ends of the optical fiber are cross-stacked to form a ring shape with a middle diameter of 5cm, and the optical fiber area where the coating layer is stripped is located in the ring area, with the left end light injection area at the bottom and the right end light collection area at the top; S2: Pass the light receiving area on the right side from the inside to the outside of the ring, and make the light injection area and the light receiving area on the same axis with the two ends facing opposite directions; S3: Pass the light-collecting area from the inside of the ring to the outside, and repeat 2-4 times to form a ring structure with a double-helix-shaped regulatory area; S4: Apply tension evenly to both ends to reduce the diameter of the ring structure to 1.8cm-2.2cm; S5: Use the outer flame of an alcohol lamp to quickly heat the double-helix shape control area to complete the production of the sensor.

5. A method for using the sensor as claimed in claim 1, characterized in that: The light receiving area at the right end of the sensor is connected to the spectrometer, and the light injection area at the left end is connected to the light source. The two ends of the sensor are clamped in the left and right translation stage fixtures, and the optical fiber is ensured to be in a straight state. The left and right translation stages are controlled to move by a strain control device. When axial strain is applied to the two ends of the sensor, due to the existence of the double-helix shape control area, the shape of the annular sensing area gradually changes from a circle to an ellipse, and the positions of the beam splitting point and the beam combining point on the semi-circular sensing area change, so that the length of the sensing area changes, and the output spectrum interference wavelength changes accordingly. The interference wavelength in the spectrometer under each strain is recorded, and the actual strain size is obtained by demodulation based on the interference wavelength.

6. A method for adjusting the performance of a sensor as claimed in claim 1, characterized in that: The diameter of the circular ring sensing area of ​​the sensor is 1.8cm-2.2cm. By selecting different diameters, the initial shape of the circular ring structure is adjusted, and then the initial positions of the beam splitting point and the beam combining point are adjusted; the number of windings of the double helix shape control area of ​​the sensor is 2-4 times. By selecting different winding times, the deformation degree of the circular ring structure during the strain process is adjusted, and then the length of the sensing area is adjusted, thereby adjusting the strain sensitivity of the sensor.

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