A sensing probe, a curvature sensor and a curvature detection method

Abstract

The embodiment of the application provides a sensing probe, a curvature sensor and a curvature detection method, the sensing probe comprising: an optical fiber, a long-period fiber grating, an M-shaped structure, a first collar, a second collar and a support body; the first collar and the second collar are fixedly arranged on the optical fiber, the long-period fiber grating is located between the first collar and the second collar and is fixedly arranged on the support body; one end of the support body is fixedly connected with the first collar, the other end of the support body is fixedly connected with the second collar, and the support body is used for supporting the long-period fiber grating; one end of the M-shaped structure is fixedly connected with the first collar, the other end of the M-shaped structure is fixedly connected with the second collar, and the center end of the M-shaped structure is not fixedly connected with the long-period fiber grating. When the optical fiber is bent, the M-shaped structure is deformed, and the curvature change amount of the optical fiber is converted into a transverse stress and applied to the long-period fiber grating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a sensing probe, a curvature sensor and a curvature detection method. BACKGROUND

[0002] Spatial curvature measurement technology can be used for structural morphology recovery and plays an important role in the fields of machinery, aerospace engineering, biology and medicine, and can be used for structural health monitoring of civil structures and infrastructures (buildings, tunnels, bridges and roads). Common curvature sensors currently include electric strain gauge type curvature sensors, capacitive type curvature sensors, laser displacement sensors and optical fiber curvature sensors. The electric strain gauge type curvature sensors cannot accurately ensure the calculation precision due to problems such as patching process; the capacitive type curvature sensors are prone to instability due to high output impedance, poor load capacity and external interference; the laser displacement sensors cannot meet the requirements of large-scale measurement; and the optical fiber curvature sensors are widely used in various fields due to small size, compact structure, high sensitivity and anti-electromagnetic interference.

[0003] Optical fiber curvature sensors are divided into two categories: one is the optical fiber grating type curvature sensor mainly based on fiber Bragg grating and long period fiber grating, and the other is the optical fiber interferometer type curvature sensor mainly based on Mach-Zehnder interferometer. When the above two types of optical fiber curvature sensors obtain curvature sensing information by modulating the center wavelength of the optical fiber grating through the transverse stress, they are also affected by temperature and / or longitudinal stress. Due to the photoelastic effect of longitudinal stress and the thermo-optic effect and thermal expansion effect of temperature, the grating pitch of the grating changes, and the effective refractive index difference of the fiber cladding and core also changes, resulting in a shift of the resonance wavelength. The above two types of optical fiber curvature sensors are very sensitive to temperature and / or longitudinal stress, so the detection accuracy of these two types of optical fiber curvature sensors is affected. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a sensing probe, a curvature sensor and a curvature detection method to improve the accuracy of curvature sensing detection. The specific technical solutions are as follows:

[0005] In a first aspect, the embodiments of the present application provide a sensing probe, which comprises:

[0006] an optical fiber, a long period fiber grating, an M-shaped structure, a first sleeve, a second sleeve and a support body;

[0007] The first loop and the second loop are fixedly arranged on the optical fiber, the long-period fiber grating is located between the first loop and the second loop and is fixedly arranged on the support body; one end of the support body is fixedly connected with the first loop, and the other end of the support body is fixedly connected with the second loop, and the support body is used for supporting the long-period fiber grating.

[0008] One end of the M-shaped structural member is fixedly connected with the first loop, the other end of the M-shaped structural member is fixedly connected with the second loop, and the center end of the M-shaped structural member is not fixedly connected with the long-period fiber grating.

[0009] In a possible implementation, in the case that the optical fiber is bent, the support body is deformed.

[0010] In a possible implementation, in the case that the optical fiber is bent, the M-shaped structural member is deformed, so that the long-period fiber grating is subjected to a transverse stress.

[0011] In a possible implementation, the long-period fiber grating is formed on the optical fiber by a phase mask method.

[0012] In a second aspect, the embodiments of the present application provide a curvature sensor, which comprises a wide-spectrum light source, an isolator, a polarizer, a polarization controller, a spectrometer, a signal processing system and the sensing probe of any one of the first aspect.

[0013] The wide-spectrum light source is connected with the isolator, the isolator is connected with the polarizer, the polarizer is connected with the polarization controller, the polarization controller is connected with the sensing probe, the sensing probe is connected with the spectrometer, and the spectrometer is connected with the signal processing system.

[0014] The wide-spectrum light source is used to emit wide-spectrum light to the isolator.

[0015] The isolator is used to prevent the wide-spectrum light from being reflected back to the wide-spectrum light source.

[0016] The polarizer is used to convert the wide-spectrum light into polarized light.

[0017] The polarization controller is used to adjust the polarization state of the polarized light, so that the polarized light meets a preset polarization state.

[0018] In the case that the optical fiber is bent, the spectrometer is used to decompose the transmitted polarized light transmitted through the long-period fiber grating into a transmission spectrum, and upload first center wavelength data and second center wavelength data in the transmission spectrum to the signal processing system.

[0019] The signal processing system is configured to receive the first center wavelength data and the second center wavelength data, calculate the absolute value of the wavelength difference between the first center wavelength and the second center wavelength, and obtain the curvature value of the optical fiber under different bending states according to the correspondence between the absolute value of the wavelength difference and the curvature value of the optical fiber measured in advance; wherein the first loss peak in the transmission spectrum corresponds to the first center wavelength, and the second loss peak in the polarization transmission spectrum corresponds to the second center wavelength.

[0020] In a possible implementation, the absolute value of the wavelength difference between the first center wavelength and the second center wavelength is in positive feedback with the curvature value of the optical fiber.

[0021] In a third aspect, the embodiments of the present application provide a curvature detection method, applied to the curvature sensor of any one of the second aspect, and the method comprises:

[0022] The wide-spectrum light source emits wide-spectrum light to the isolator;

[0023] The isolator prevents the wide-spectrum light from being reflected back to the wide-spectrum light source;

[0024] The polarizer converts the wide-spectrum light into polarized light;

[0025] The polarization controller adjusts the polarization state of the polarized light so that the polarized light meets the preset polarization state;

[0026] In the case that the optical fiber is bent, the spectrometer decomposes the transmission polarized light transmitted through the long-period fiber grating into a transmission spectrum, and uploads the first center wavelength data and the second center wavelength data in the transmission spectrum to the signal processing system;

[0027] The signal processing system receives the first center wavelength data and the second center wavelength data, calculates the absolute value of the wavelength difference between the first center wavelength and the second center wavelength, and obtains the curvature value of the optical fiber under different bending states according to the correspondence between the absolute value of the wavelength difference and the curvature value of the optical fiber measured in advance, so that the curvature sensor performs curvature sensing detection; wherein the first loss peak in the transmission spectrum corresponds to the first center wavelength, and the second loss peak in the polarization transmission spectrum corresponds to the second center wavelength.

[0028] In a possible implementation, in the case that the optical fiber is not bent, the spectrometer decomposes the transmission polarized light transmitted through the long-period fiber grating into a transmission spectrum, and uploads the third center wavelength data in the transmission spectrum to the signal processing system;

[0029] The signal processing system receives the third center wavelength data and obtains the result that the optical fiber has not bent.

[0030] In one possible implementation, the third loss peak in the transmission spectrum corresponds to the third center wavelength when the optical fiber does not bend.

[0031] In one possible implementation, the support does not deform and the M-shaped structural member does not deform if the optical fiber does not bend.

[0032] Beneficial effects of the embodiments in this application:

[0033] This application provides a sensing probe, curvature sensor, and curvature detection method. The sensing probe includes: an optical fiber, a long-period fiber grating, an M-shaped structural component, a first collar, a second collar, and a support. The first and second collars are fixedly mounted on the optical fiber. The long-period fiber grating is located between the first and second collars and is fixedly mounted on the support. One end of the support is fixedly connected to the first collar, and the other end is fixedly connected to the second collar, supporting the long-period fiber grating. One end of the M-shaped structural component is fixedly connected to the first collar, and the other end is fixedly connected to the second collar. The center end of the M-shaped structural component is not in fixed contact with the long-period fiber grating. When the optical fiber bends, the M-shaped structural component deforms, converting the change in fiber curvature into lateral stress applied to the long-period fiber grating.

[0034] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0036] Figure 1 This is a schematic diagram of a first structure of the sensing probe provided in an embodiment of this application;

[0037] Figure 2 This is a schematic diagram of a second structure of the sensing probe provided in an embodiment of this application;

[0038] Figure 3a This is a schematic diagram of the structure of a curvature sensor provided in an embodiment of this application;

[0039] Figure 3b a schematic diagram of a transmission spectrum of a long-period fiber grating when the long-period fiber grating is subjected to a transverse stress;

[0040] Figure 4 a first flowchart of a curvature detection method provided by an embodiment of the present application;

[0041] Figure 5a a second flowchart of a curvature detection method provided by an embodiment of the present application;

[0042] Figure 5b a schematic diagram of a transmission spectrum of a long-period fiber grating when the long-period fiber grating is not subjected to a transverse stress. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art based on the present application are within the scope of protection of the present application.

[0044] The fiber curvature sensor in the related art obtains curvature sensing information by modulating the center wavelength of a fiber grating by a transverse stress, that is, the curvature sensing information is converted into the movement of the center wavelength of the grating, and the measurement of the curvature sensing information is realized by demodulating the center wavelength offset from the measured optical signal, but the measurement method is affected by temperature and / or longitudinal stress. Due to the photoelastic effect of the longitudinal stress and the thermo-optic effect and thermal expansion effect of the temperature, the grating pitch of the grating changes, and the effective refractive index difference of the fiber cladding and the core also changes, which causes the resonance wavelength to shift and affects the curvature sensing detection result. In summary, the fiber curvature sensor in the related art is very sensitive to temperature and / or longitudinal stress, and therefore, the curvature sensing detection accuracy of the fiber curvature sensor is low.

[0045] In order to improve the accuracy of curvature sensing detection, an embodiment of the present application provides a sensing probe 5, as shown in Figure 1 The sensing probe 5 comprises:

[0046] a fiber 51, a long-period fiber grating 52, an M-shaped structure 53, a first sleeve 54, a second sleeve 55, and a support body 56.

[0047] The first collar 54 and the second collar 55 are fixedly arranged on the optical fiber 51, and the long-period fiber grating 52 is arranged between the first collar 54 and the second collar 55 and is fixedly arranged on the support body 56; one end of the support body 56 is fixedly connected with the first collar 54, and the other end of the support body 56 is fixedly connected with the second collar 55, and the support body 56 is used for supporting the long-period fiber grating 52.

[0048] One end of the M-shaped structural member 53 is fixedly connected with the first collar 54, and the other end of the M-shaped structural member 53 is fixedly connected with the second collar 55, and the center end of the M-shaped structural member 53 is not fixedly connected with the long-period fiber grating 52.

[0049] The optical fiber, i.e., the optical waveguide fiber, is a kind of fiber made of glass or plastic and used as an optical transmission tool. The fiber grating is a kind of diffraction grating formed by axially periodically modulating the refractive index of the fiber core through a certain method and is a kind of passive filter device. The long-period fiber grating is a kind of fiber grating with a period of dozens to hundreds of microns, and the coupling between the core mode and the cladding mode of the same direction transmission has no backward reflection and belongs to a transmission type band rejection filter. Since the resonance wavelength of the long-period fiber grating is sensitive to the changes of stress and temperature, the long-period fiber grating is mainly used for measuring stress and temperature.

[0050] The first collar and the second collar are two same collars, which can be made of plastic material, and the first collar and the second collar can be fixed on the optical fiber through the gluing mode. The M-shaped structural member can be made of metal, which can be copper, iron, aluminum or the like. The M-shaped structural member can be fixedly connected with the first collar and the second collar through the gluing mode, and solvent type glue or water-based glue can be used for bonding. The support body is a long strip-shaped flexible plastic member, and the long-period fiber grating can be fixed on the support body through the gluing mode.

[0051] It should be noted that the "not fixedly connected" in the "not fixedly connected" between the center end of the M-shaped structural member and the long-period fiber grating means that the center end of the M-shaped structural member only contacts the long-period fiber grating, but is not fixedly connected together.

[0052] In a possible implementation, referring to Figure 2 In the case that the optical fiber 51 is bent, the support body 56 is deformed.

[0053] In a possible implementation, referring to Figure 2 In the case that the optical fiber 51 is bent, the M-shaped structural member 53 is deformed, so that the long-period fiber grating 52 is subjected to a transverse stress.

[0054] In the embodiment of the present application, when the optical fiber is bent, the M-shaped structure is deformed, and the change in the curvature of the optical fiber is converted into a transverse stress applied to the long-period fiber grating.

[0055] In a possible implementation, the long-period fiber grating 52 is formed on the optical fiber 51 by a phase mask method.

[0056] The long-period fiber grating in the present application is made on the optical fiber by a phase mask method. The phase mask method is simple, low in cost, and low in precision requirement, and can be used to customize fiber gratings with different transmission wavelengths.

[0057] The embodiment of the present application also provides a curvature sensor, referring to Figure 3a , the curvature sensor comprises a wide-spectrum light source 1, an isolator 2, a polarizer 3, a polarization controller 4, a spectrometer 6, a signal processing system 7, and the sensing probe 5 in any of the above embodiments.

[0058] The wide-spectrum light source 1 is connected with the isolator 2, the isolator 2 is connected with the polarizer 3, the polarizer 3 is connected with the polarization controller 4, the polarization controller 4 is connected with the sensing probe 5, the sensing probe 5 is connected with the spectrometer 6, and the spectrometer 6 is connected with the signal processing system 7.

[0059] The wide-spectrum light source 1 is configured to emit wide-spectrum light to the isolator 2.

[0060] The isolator 2 is configured to prevent the wide-spectrum light from being reflected back to the wide-spectrum light source.

[0061] The isolator is a passive optical device that allows unidirectional light to pass through, and can prevent the wide-spectrum light in the optical path from being reflected back to the wide-spectrum light source, thereby affecting the wide-spectrum light source system.

[0062] The polarizer 3 is configured to convert the wide-spectrum light into polarized light.

[0063] The polarization controller 4 is configured to adjust the polarization state of the polarized light, so that the polarized light meets a preset polarization state.

[0064] In the case where the optical fiber 51 is bent, the spectrometer 6 is configured to decompose the transmitted polarized light transmitted through the long-period fiber grating 52 into a transmission spectrum, and upload first center wavelength data and second center wavelength data in the transmission spectrum to the signal processing system 7.

[0065] The signal processing system 7 is used to receive the first center wavelength data and the second center wavelength data, calculate the absolute value of the wavelength difference between the first center wavelength and the second center wavelength, and obtain the curvature value of the optical fiber 51 under different bending states according to the correspondence between the pre-measured absolute value of the wavelength difference and the optical fiber curvature value; wherein, the first loss peak in the transmission spectrum corresponds to the first center wavelength, and the second loss peak in the polarized light transmission spectrum corresponds to the second center wavelength.

[0066] In one possible implementation, the absolute value of the wavelength difference between the first center wavelength and the second center wavelength is positively correlated with the fiber curvature value.

[0067] When an optical fiber bends, it causes deformation in the support structure and the M-shaped structural component. This deformation converts the change in fiber curvature into lateral stress, which is applied to the long-period fiber grating (FBG). When the FBG is subjected to this lateral stress, the polarization modes of the polarized light wave separate, resulting in two different coupling center wavelengths (a first center wavelength and a second center wavelength) corresponding to the same FBG. This is reflected in the transmission spectrum of the FBG as two loss peaks. It can be understood that when polarized light passes through the FBG, the light wave with the lowest loss occurs at the transmission wavelength, which is the center wavelength and has the highest energy. See the example below. Figure 3b This is a schematic diagram of the transmission spectrum of a long-period fiber grating under transverse stress. The horizontal axis represents the wavelength λ of the transmitted polarized light (in nm), and the vertical axis represents the transmission loss φ (in dB). The first loss peak LP11 corresponds to the first center wavelength λ. 11 The second loss peak LP12 corresponds to the second center wavelength λ. 12 After the spectrometer detects the first loss peak LP11 and the second loss peak LP12, it uploads the loss peak data, i.e., the center wavelength data, to the signal processing system. The signal processing system is used to calculate the first center wavelength λ. 11 With the second center wavelength λ 12 The absolute value of the wavelength difference between them is |Δλ| = |λ 12 -λ 11 |Δλ| represents the spectral spacing between loss peaks, and the curvature θ of the fiber in its current bent state is obtained according to the pre-measured correspondence between the absolute value of the wavelength difference |Δλ| and the fiber curvature θ. The correspondence between the absolute value of the wavelength difference |Δλ| and the fiber curvature θ can be pre-measured through simulation calculation and sensor calibration.

[0068] In one example, the sensing probe of the curvature sensor is arranged in a scene with a known curvature value θ, the absolute value |Δλ| of the wavelength difference between the first center wavelength and the second center wavelength in the transmission spectrum of the sensing probe in the current bending state is measured, and the measured absolute value |Δλ| of the wavelength difference is recorded, and a correspondence between the absolute value |Δλ| and the curvature value θ is established. Other scenes with known curvature values are selected for measurement, and a correspondence between different curvature values θ and absolute values |Δλ| is established.

[0069] When the fiber is bent to a greater extent, the curvature is greater, the transverse stress applied by the M-shaped structure is greater, and the absolute value of the wavelength difference in the further transmission spectrum, i.e., the spectral interval, is gradually increased. By detecting the change in the absolute value |Δλ| of the wavelength difference in the transmission spectrum, the change in the curvature value θ of the fiber can be obtained, i.e., the curvature sensing detection can be achieved.

[0070] When the external temperature and / or the longitudinal stress cause the center wavelength of the long-period fiber grating to shift, since the spectral interval, i.e., the absolute value |Δλ| of the wavelength difference, in the transmission spectrum is detected, even if the temperature and / or the longitudinal stress causes the center wavelength to shift, the subtraction of the first center wavelength from the second center wavelength can offset the influence (shifted center wavelength) of the temperature and / or the longitudinal stress, thereby reducing the influence of the temperature and / or the longitudinal stress on the curvature sensing detection result. Therefore, the sensing probe in the present application has the advantage of being insensitive to temperature and / or longitudinal stress. In the related art, the curvature sensing information is obtained by modulating the center wavelength of the fiber grating by the transverse stress, i.e., the curvature sensing information is converted into the movement of the center wavelength of the grating, and the measurement of the curvature sensing information is realized by demodulating the center wavelength shift from the measured optical signal, but it is affected by the temperature and / or the longitudinal stress, resulting in low curvature sensing detection accuracy. Compared with the curvature sensing detection in the related art, the curvature sensor provided in the present application reduces the influence of the temperature and / or the longitudinal stress on the curvature sensing detection result, and improves the accuracy of the curvature sensing detection.

[0071] The curvature sensor in the present application adopts an all-optical design, the optical path and the device are integrated by an optical fiber, the anti-electromagnetic interference capability is strong, no reference electrode is needed, the accuracy is high, and the reliability is strong.

[0072] In the embodiments of the present application, the change in the curvature of the fiber is obtained by detecting the absolute value of the wavelength difference between the two center wavelengths, the greater the absolute value of the wavelength difference, the greater the curvature of the fiber, and the greater the bending degree. When the temperature and / or the longitudinal stress causes the center wavelength to shift, the influence of the temperature and / or the longitudinal stress can be offset by subtracting the first center wavelength from the second center wavelength, the influence of the temperature and / or the longitudinal stress on the curvature sensing detection result is reduced, and the accuracy of the curvature sensing detection is improved.

[0073] The embodiment of the present application also provides a curvature detection method, which is applied to the curvature sensor in any of the above-mentioned embodiments, and refers to Figure 4 A first flowchart of the curvature detection method provided by the embodiment of the present application comprises the following steps:

[0074] In step S401, the wide-spectrum light source emits wide-spectrum light to the isolator.

[0075] In step S402, the isolator prevents the wide-spectrum light from being reflected back to the wide-spectrum light source.

[0076] In step S403, the polarizer converts the wide-spectrum light into polarized light.

[0077] In step S404, the polarization controller adjusts the polarization state of the polarized light so that the polarized light meets a preset polarization state.

[0078] In step S405, when the optical fiber is bent, the spectrometer decomposes the transmitted polarized light transmitted through the long-period fiber grating into a transmission spectrum, and uploads first center wavelength data and second center wavelength data in the transmission spectrum to the signal processing system.

[0079] In step S406, the signal processing system receives the first center wavelength data and the second center wavelength data, calculates the absolute value of the wavelength difference between the first center wavelength and the second center wavelength, and obtains the curvature value of the optical fiber under different bending states according to the corresponding relationship between the absolute value of the wavelength difference and the curvature value of the optical fiber measured in advance, so that the curvature sensor performs curvature sensing detection. Wherein the first loss wave peak in the transmission spectrum corresponds to the first center wavelength, and the second loss wave peak in the polarized light transmission spectrum corresponds to the second center wavelength.

[0080] The specific analysis of the curvature detection method is the same as above, which will not be repeated here.

[0081] In the embodiment of the present application, the curvature change of the optical fiber is obtained by detecting the absolute value of the wavelength difference of the two center wavelengths. The greater the absolute value of the wavelength difference, the greater the curvature of the optical fiber, and the greater the bending degree. When the center wavelengths are offset due to temperature and / or longitudinal stress, the influence of temperature and / or longitudinal stress can be offset by subtracting the first center wavelength from the second center wavelength, reducing the influence of temperature and / or longitudinal stress on the curvature sensing detection result, and improving the accuracy of the curvature sensing detection.

[0082] In a possible implementation, referring to Figure 5a A second flowchart of the curvature detection method provided by the embodiment of the present application comprises the following steps:

[0083] Step S501, in the case that the optical fiber does not bend, the transmitted polarized light transmitted through the long period fiber grating is decomposed into a transmission spectrum by the optical spectrum analyzer, and third center wavelength data in the transmission spectrum is uploaded to the signal processing system.

[0084] Step S502, the third center wavelength data is received by the signal processing system, and a result that the optical fiber does not bend is obtained.

[0085] In a possible implementation, in the case that the optical fiber does not bend, a third loss peak in the transmission spectrum corresponds to the third center wavelength.

[0086] In one example, referring to Figure 5b is a schematic diagram of a transmission spectrum of the long period fiber grating when the long period fiber grating is not subjected to lateral stress, and the optical spectrum analyzer only detects one loss peak, i.e., a third loss peak LP01, and the third loss peak LP01 corresponds to a third center wavelength λ1.

[0087] In a possible implementation, in the case that the optical fiber does not bend, the support body does not deform, and the M-shaped structure does not deform.

[0088] It should be noted that, in the present document, the relationship terms such as first and second are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or sequence between the entities or operations. Moreover, the terms “include”, “contain” or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement “including a…” does not exclude the presence of another identical element in the process, method, article or device including the element.

[0089] Each of the embodiments in the present specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each of the embodiments mainly explains the difference from other embodiments. In particular, for the system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the related parts can be referred to the part of the description of the method embodiments.

[0090] The above only describes the preferred embodiments of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sensing probe, characterized by, The sensing probe comprises: an optical fiber, a long-period fiber grating, an M-shaped structure, a first collar, a second collar, and a support body; the first collar and the second collar are fixedly arranged on the optical fiber, the long-period fiber grating is located between the first collar and the second collar and is fixedly arranged on the support body; one end of the support body is fixedly connected with the first collar, and the other end of the support body is fixedly connected with the second collar, and the support body is used for supporting the long-period fiber grating; one end of the M-shaped structure is fixedly connected with the first collar, and the other end of the M-shaped structure is fixedly connected with the second collar, and the center end of the M-shaped structure is not fixedly connected with the long-period fiber grating.

2. The sensing probe of claim 1, wherein, In the case that the optical fiber is bent, the support body is deformed.

3. The sensing probe of claim 2, wherein, In the case that the optical fiber is bent, the M-shaped structure is deformed, so that the long-period fiber grating is subjected to a transverse stress.

4. The sensing probe of claim 1, wherein, The long-period fiber grating is formed on the optical fiber by a phase mask method.

5. A curvature sensor characterized by, The curvature sensor comprises a wide-spectrum light source, an isolator, a polarizer, a polarization controller, a spectrometer, a signal processing system, and the sensing probe according to any one of claims 1-4; the wide-spectrum light source is connected with the isolator, the isolator is connected with the polarizer, the polarizer is connected with the polarization controller, the polarization controller is connected with the sensing probe, the sensing probe is connected with the spectrometer, and the spectrometer is connected with the signal processing system; the wide-spectrum light source is used for emitting wide-spectrum light to the isolator; the isolator is used for preventing the wide-spectrum light from being reflected back to the wide-spectrum light source; the polarizer is used for converting the wide-spectrum light into polarized light; the polarization controller is used for adjusting the polarization state of the polarized light, so that the polarized light meets a preset polarization state; in the case that the optical fiber is bent, the spectrometer is used for decomposing the transmitted polarized light transmitted through the long-period fiber grating into a transmission spectrum, and uploading first center wavelength data and second center wavelength data in the transmission spectrum to the signal processing system; the signal processing system is used for receiving the first center wavelength data and the second center wavelength data, calculating the absolute value of the wavelength difference between the first center wavelength and the second center wavelength, and obtaining the curvature value of the optical fiber under different bending states according to the corresponding relationship between the absolute value of the wavelength difference and the curvature value of the optical fiber which is measured in advance; wherein the first loss wave peak in the transmission spectrum corresponds to the first center wavelength, and the second loss wave peak in the polarized light transmission spectrum corresponds to the second center wavelength.

6. The curvature sensor of claim 5, wherein, The absolute value of the wavelength difference between the first center wavelength and the second center wavelength and the curvature value of the optical fiber are in positive feedback.

7. A curvature detection method characterized by, The method is applied to the curvature sensor according to any one of claims 5-6, and the method comprises: emitting wide-spectrum light to the isolator by the wide-spectrum light source; preventing the wide-spectrum light from being reflected back to the wide-spectrum light source by the isolator; converting the wide-spectrum light into polarized light by the polarizer; The polarization state of the polarized light is adjusted by the polarization controller, so that the polarized light meets a preset polarization state; In the case that the optical fiber is bent, the transmitted polarized light transmitted through the long-period fiber grating is decomposed into a transmission spectrum by the optical spectrum analyzer, and first center wavelength data and second center wavelength data in the transmission spectrum are uploaded to the signal processing system; The signal processing system receives the first center wavelength data and the second center wavelength data, calculates the absolute value of the wavelength difference between the first center wavelength and the second center wavelength, and obtains the curvature value of the optical fiber under different bending states according to the corresponding relationship between the absolute value of the wavelength difference and the curvature value of the optical fiber measured in advance, so that the curvature sensor performs curvature sensing detection; wherein the first loss wave peak in the transmission spectrum corresponds to the first center wavelength, and the second loss wave peak in the polarization transmission spectrum corresponds to the second center wavelength.

8. The method of claim 7, wherein, In the case that the optical fiber is not bent, the transmitted polarized light transmitted through the long-period fiber grating is decomposed into a transmission spectrum by the optical spectrum analyzer, and third center wavelength data in the transmission spectrum is uploaded to the signal processing system; The signal processing system receives the third center wavelength data to obtain the result that the optical fiber is not bent.

9. The method of claim 8, wherein, In the case that the optical fiber is not bent, the third loss wave peak in the transmission spectrum corresponds to the third center wavelength.

10. The method of claim 9, wherein, In the case that the optical fiber is not bent, the support body does not deform, and the M-shaped structure does not deform.

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