Cable stress monitoring method based on fiber bragg grating axial force sensor

Abstract

The invention discloses a cable stress monitoring method based on an optical fiber grating axial force sensor, and relates to the technical field of optical fiber sensors. Comprising the following steps: installing a fiber bragg grating axial force sensor in an electric connector, and butting the fiber bragg grating axial force sensor with a to-be-tested cable; applying an axial force to the to-be-measured cable, enabling the stress tube to generate strain, and obtaining the wavelength increment of the metallized grating; based on the wavelength increment, carrying out axial force calibration through a fiber bragg grating axial force sensor, and establishing a relation coefficient between the wavelength increment and strain; and obtaining a stress parameter value of the to-be-measured cable based on the relation coefficient between the wavelength increment and the strain, and forming a stress tendency chart of the to-be-measured cable to be displayed in the optical fiber sensing analyzer. The stress condition of the cable in the electric connector can be monitored in real time, meanwhile, the stress condition of each pinhole cable wire can be monitored in real time so as to realize risk prediction, and the monitoring accuracy and timeliness are obviously superior to those of traditional cable stress monitoring.

Description

Technical Field

[0001] This application relates to the technical field of fiber optic sensors, and particularly to a method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor. Background Art

[0002] Compared with traditional electrical sensors, fiber optic sensors have very obvious technical advantages in sensing network applications: such as small size, light weight, very good reliability and stability; passive system, low energy dependence, which can greatly save the cost of power supply equipment and lines, and is suitable for long-distance use; anti-electromagnetic interference, anti-corrosion, completely unaffected by lightning, and can work in harsh chemical environments, field environments and strong electromagnetic interference and other places; no radiation, no flammable and explosive materials, waterproof, environmentally friendly, etc. Fiber Bragg Grating (FBG for short) is a sensitive area about 10 mm long axially processed in a quartz single-mode fiber by using a laser irradiation method, which can selectively reflect narrowband light that satisfies the Bragg condition and return along the original incident light path, while light signals of other wavelengths are normally transmitted. The wavelength of the reflected narrowband light changes linearly with temperature and strain, so it can be used for the measurement of various physical quantities. Aircraft cables, automotive cables, ship cables and other industrial cable conductors will generate stress in the tensile state, and it is necessary to monitor the cable conductors in real time to achieve risk prediction. Traditional cable stress monitoring methods generally use electrical sensors, but their monitoring accuracy and timeliness are not high. Based on this, this application proposes a method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor. B The narrowband light is selectively reflected and returns along the original incident light path, while light signals of other wavelengths are normally transmitted. The wavelength of the reflected narrowband light changes linearly with temperature and strain, so it can be used for the measurement of various physical quantities. Aircraft cables, automotive cables, ship cables and other industrial cable conductors will generate stress in the tensile state, and it is necessary to monitor the cable conductors in real time to achieve risk prediction. Traditional cable stress monitoring methods generally use electrical sensors, but their monitoring accuracy and timeliness are not high. Based on this, this application proposes a method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor. Summary of the Invention

[0003] The main purpose of this application is to provide a method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor, aiming to solve the technical problem of low accuracy of the existing cable force monitoring methods.

[0004] To achieve the above object, this application proposes a method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor, which uses a fiber optic sensing analyzer to monitor the force on the cable to be measured in real time. A fiber Bragg grating axial force sensor is provided in the channel of the fiber optic sensing analyzer, and the fiber Bragg grating axial force sensor includes a stress tube and a metallized grating fixed in the stress tube;

[0005] The method includes the following steps:

[0006] Install the fiber Bragg grating axial force sensor in an electrical connector and dock it with the cable to be measured;

[0007] Apply an axial force to the cable to be measured to cause the stress tube to strain, and obtain the wavelength increase of the metallized grating;

[0008] Based on the wavelength increase amount, axial force calibration is performed through the fiber grating axial force sensor, and a relationship coefficient between the wavelength increase amount and strain is established;

[0009] Based on the relationship coefficient between the wavelength increase amount and strain, the force parameter value of the cable to be measured is obtained, and a force trend graph of the cable to be measured is formed and displayed in the fiber optic sensing analyzer.

[0010] Optionally, the preparation steps of the metallized grating include:

[0011] Remove the coating layer on the surface of the optical fiber, then scratch the diffraction grating, and coat the transition metal on the surface of the optical fiber and the grating area to obtain a pre-treated fiber grating;

[0012] Weld a section of metal tube at both ends of the pre-treated fiber grating through glass solder to obtain the metallized grating.

[0013] Optionally, the metallized grating is welded and fixed in the stress tube through the metal tubes at both ends.

[0014] Optionally, the fiber grating axial force sensor further includes an adapter, a housing, and a wire pin. One end of the adapter is connected to the stress tube, and the other end is connected to the housing. The adapter and the housing can conduct axial force, and the wire pin is fixed in the housing.

[0015] Optionally, the fiber grating axial force sensor further includes a circlip and a retaining ring. The wire pin is connected to the circlip and axially limited through the circlip. The retaining ring is welded and fixed on the housing and limits the circlip inside the housing.

[0016] Optionally, the fiber grating axial force sensor further includes a connector;

[0017] The steps of installing the fiber grating axial force sensor in the electrical connector include:

[0018] Threadedly connect the fiber grating axial force sensor to the electrical connector through the connector, so that the fiber grating axial force sensor is fixedly installed in the electrical connector.

[0019] Optionally, the steps of applying an axial force to the cable to be measured to cause the stress tube to strain and obtaining the wavelength increase amount of the metallized grating include:

[0020] Apply weights to the electrical connector, start the fiber optic sensing analyzer, apply different magnitudes of force to the electrical connector by changing the weight of the weights, cause the stress tube to sense stress and undergo strain elongation, and simultaneously stretch the metallized grating, causing the wavelength of the metallized grating to increase. Obtain the increase in the wavelength of the metallized grating through the fiber optic sensing analyzer.

[0021] Optionally, the fiber optic sensing analyzer is provided with 32 channels.

[0022] Optionally, multiple fiber grating axial force sensors are provided in each channel of the fiber optic sensing analyzer.

[0023] Optionally, at least one temperature sensor is further provided in one of the channels of the fiber optic sensing analyzer.

[0024] The beneficial effects of this application include:

[0025] In this application, a fiber grating axial force sensor is added inside the electrical connector. When the fiber grating axial force sensor is in an unloaded state, the metallized grating is in a pre-tensioned and straightened state inside the stress tube. By applying different magnitudes of force to the electrical connector, the force on the electrical connector will be transmitted to the fiber grating axial force sensor. Using the fiber grating axial force sensor to sense stress, when the internal stress tube undergoes strain elongation, it will simultaneously stretch the metallized grating, causing the wavelength of the metallized grating to increase. The amount of stretching and the increase in wavelength show a linear relationship. Then, through the axial force calibration of the fiber grating axial force sensor, the relationship coefficient between the increase in wavelength and strain can be obtained, and thus the axial force can be measured. The fiber optic sensing analyzer can obtain the wavelength information of the metallized grating and display the change in the magnitude of the applied axial force synchronously in the fiber optic sensing analyzer, thereby real-time monitoring the stress condition of the cable inside the electrical connector. Its monitoring accuracy and timeliness are significantly better than traditional cable stress monitoring. At the same time, this method can real-time monitor the stress condition of each pinhole cable conductor to achieve risk prediction, and is applicable to the stress monitoring of various industrial cables such as aircraft cables, automotive cables, and ship cables. Its accuracy is relatively high, and the stress condition of the cable can be quickly obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0027] Figure 1 It is a schematic structural diagram of the fiber grating axial force sensor described in the embodiments of the present application;

[0028] Figure 2 Schematic diagram of the assembly of the fiber Bragg grating axial force sensor described in the embodiments of the present application within an electrical connector;

[0029] Figure 3 Force analysis diagram of the cable to be measured described in the embodiments of the present application.

[0030] Reference numerals:

[0031] 1 - Connector; 2 - Metallized grating; 3 - Stress tube; 4 - Adapter; 5 - Housing; 6 - Pin with wire; 7 - Snap ring; 8 - Retaining ring.

[0032] The realization, functional features and advantages of the objectives of the present application will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0033] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0034] In view of the technical problems existing in the prior art, the embodiments of the present application provide a method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor. A fiber optic sensing analyzer is used to monitor the force on the cable to be measured in real time. A fiber Bragg grating axial force sensor is provided in the channel of the fiber optic sensing analyzer. The fiber Bragg grating axial force sensor includes a stress tube and a metallized grating fixed within the stress tube;

[0035] The method includes the following steps:

[0036] Install the fiber Bragg grating axial force sensor within an electrical connector and dock it with the cable to be measured;

[0037] Apply an axial force to the cable to be measured to cause the stress tube to strain, and obtain the wavelength increase of the metallized grating;

[0038] Based on the wavelength increase, perform axial force calibration through the fiber Bragg grating axial force sensor to establish the relationship coefficient between the wavelength increase and strain;

[0039] Based on the relationship coefficient between the wavelength increase and strain, obtain the force parameter value of the cable to be measured, and form a force trend diagram of the cable to be measured for display in the fiber optic sensing analyzer.

[0040] The fiber Bragg grating axial force sensor of the present application includes a stress tube and a metallized grating fixed inside the stress tube. The stress tube is the main component of the fiber Bragg grating axial force sensor to sense stress, and the metallized grating installed inside it can measure this stress.

[0041] In the present application, a fiber Bragg grating axial force sensor is added inside the electrical connector. When the fiber Bragg grating axial force sensor is in an unloaded state, the metallized grating is in a pre-tensioned and straightened state inside the stress tube. By applying different magnitudes of force to the electrical connector, the force on the electrical connector will be transmitted to the fiber Bragg grating axial force sensor. Using the fiber Bragg grating axial force sensor to sense stress, when the internal stress tube undergoes strain elongation, it will synchronously stretch the metallized grating, causing an increase in the wavelength of the metallized grating. And there is a linear relationship between the elongation of the stress tube and the increase in wavelength. Then, by calibrating the axial force of the fiber Bragg grating axial force sensor, the relationship coefficient between the increase in wavelength and strain can be obtained, and thus the axial force can be measured. The fiber optic sensing analyzer can obtain the wavelength information of the metallized grating and display the change in the magnitude of the applied axial force synchronously in the fiber optic sensing analyzer, so as to monitor the stress condition of the cable inside the electrical connector in real time. Its monitoring accuracy and timeliness are significantly better than those of traditional cable stress monitoring. At the same time, this method can monitor the stress condition of each pinhole cable conductor in real time to achieve risk prediction, and can be applied to the stress monitoring of various industrial cables such as aircraft cables, automotive cables, and ship cables. Its accuracy is relatively high, and the stress condition of the cable can be obtained quickly.

[0042] Specifically, the axial force calibration of the sensor is achieved by pre-tensioning the sensor, which causes the internal stress tube to be stressed and stretched, resulting in a change in the wavelength of the metallized grating. By establishing the relationship coefficient between the amount of stress-induced stretching of the stress tube and the increase in wavelength, and since the fiber can detect the change in wavelength and the grating can detect the change in force, the measurement of the axial force is realized through the established relationship coefficient between the amount of stress-induced stretching of the stress tube and the increase in wavelength.

[0043] Specifically, since the metallized grating can selectively reflect narrowband light that satisfies the Bragg condition for a specific central wavelength λ B and return it along the original incident light path, while light signals of other wavelengths are normally transmitted. The central λ B satisfies the following conditions:

[0044] λ B = 2n eff Λ

[0045] where:

[0046] n eff is the effective refractive index of the fiber core layer, which is determined by the material itself;

[0047] Λ is the grating spatial period, which is the spatial period of the refractive index modulation determined during grating writing.

[0048] Since the wavelength of the reflected narrowband light can vary linearly with strain, the relationship coefficient between the wavelength increase and strain can be obtained through the axial force calibration of the fiber Bragg grating axial force sensor, and then the measurement of the cable axial force can be realized.

[0049] As an implementable embodiment of the present application, the preparation steps of the metallized grating include:

[0050] Remove the coating layer on the surface of the optical fiber, then scratch the diffraction grating, and coat the transition metal on the surface of the optical fiber and the grating area to obtain a pre-treated fiber grating;

[0051] Weld a section of metal tube at both ends of the pre-treated fiber grating through glass solder to obtain the metallized grating.

[0052] In the specific implementation process, the metallized grating is welded and fixed in the stress tube through the metal tubes at both ends. The outer diameter of the ordinary single-mode bare optical fiber is 0.125 mm, and it is not easy to install and fix. The present application adopts the thermal stripping coating process to remove the coating layer of the optical fiber without damaging the optical fiber, then scratch the diffraction grating, and coat the transition metal to improve the tensile strength of the fiber grating. Then, a section of metal tube with a length of 5 mm and an outer diameter of φ0.9 mm is welded at both ends of the fiber grating to make a metallized grating. The metallized grating can be welded and fixed on the metal structure - the stress tube by welding, which is beneficial to the installation and fixation of the metallized grating and also improves the tensile strength of the metallized grating.

[0053] As an implementable embodiment of the present application, the fiber Bragg grating axial force sensor further includes an adapter, a housing, and a wire pin. One end of the adapter is connected to the stress tube, and the other end is connected to the housing. The adapter and the housing can conduct the axial force, and the wire pin is fixed in the housing.

[0054] Specifically, one end of the adapter is connected to the stress tube, and the other end is connected to the housing. After applying an axial force to the electrical connector, the axial force can be conducted through the adapter and the housing, and then the stress tube can sense the stress and elongate.

[0055] As an implementable embodiment of the present application, the fiber Bragg grating axial force sensor further includes a circlip and a retaining ring. The wire pin is connected to the circlip and axially limited by the circlip. The retaining ring is welded and fixed on the housing to limit the circlip inside the housing.

[0056] Specifically, the snap ring is a structural component taken out from the electrical connector. The wire - carrying pin is axially limited by the snap ring, and this method is the same as the fixing method of the pin in the electrical connector. In this way, it can be ensured that the installation and fixing method of the wire - carrying pin is consistent with the installation and fixing method in the electrical connector, and the wire - carrying pin can be disassembled and replaced. Then, by welding the retaining ring to the housing, the snap ring can be restricted inside the housing.

[0057] As an implementable mode of the present application, the fiber Bragg grating axial force sensor further includes a connector.

[0058] The step of installing the fiber Bragg grating axial force sensor into the electrical connector includes:

[0059] Thread - connect the fiber Bragg grating axial force sensor to the electrical connector through the connector, so that the fiber Bragg grating axial force sensor is fixedly installed inside the electrical connector.

[0060] By thread - connecting the connector to the electrical connector, the installation and disassembly of the fiber Bragg grating axial force sensor can be quickly realized, and the reliability of the connection between the fiber Bragg grating axial force sensor and the cable can be ensured.

[0061] As an implementable mode of the present application, the step of applying an axial force to the cable to be measured to cause the stress tube to strain and obtaining the wavelength increase amount of the metallized grating includes:

[0062] Apply weights to the electrical connector, start the fiber optic sensing analyzer, apply different magnitudes of force to the electrical connector by changing the weight of the weights, so that the stress tube senses stress and strains and elongates, and simultaneously stretch the metallized grating to increase the wavelength of the metallized grating. Obtain the wavelength increase amount of the metallized grating through the fiber optic sensing analyzer.

[0063] Specifically, by applying weights to the electrical connector, a certain force is applied to the cable to be measured. By changing the weight of the weights, the force on the fiber Bragg grating axial force sensor connected to the cable to be measured is also constantly changing. As a result, the stress tube strains and elongates, and the wavelength of the metallized grating increases linearly synchronously. Then, obtain the wavelength increase amount of the metallized grating through the fiber optic sensing analyzer, and further obtain the relationship coefficient between the wavelength increase amount and the strain, so that the change in the magnitude of the applied axial force can be synchronously displayed in the fiber optic sensing analyzer. Since there is a certain gap between the connection of the cable and the fiber Bragg grating, the magnitude of the reflected tensile force does not completely match the weight of the weights, and the error is within the expected range of 1N - 2N.

[0064] As an implementable mode of the present application, the fiber optic sensing analyzer is provided with 32 channels. The present application adopts a hermetically sealed modular design for the 32-channel fiber optic sensing analyzer, which can obtain the wavelength information of the metallized grating in real time and synchronously display the change in the magnitude of the applied axial force in the fiber optic sensing analyzer, thereby realizing the measurement of the axial force.

[0065] As an implementable mode of the present application, a plurality of the fiber grating axial force sensors are provided in each channel of the fiber optic sensing analyzer. Through the plurality of fiber grating axial force sensors, multi-point quasi-distributed measurement can be carried out, thereby improving the accuracy of the force condition of the cable.

[0066] As an implementable mode of the present application, at least one temperature sensor is further provided in one of the channels of the fiber optic sensing analyzer.

[0067] In the specific implementation process, the change in temperature in the environment may also cause the wavelength of the metallized grating to change. To avoid the influence of the temperature variable in the environment on the accuracy of the cable force monitoring caused by the wavelength change, the present application is provided with at least one temperature sensor in one of the channels of the fiber optic sensing analyzer. Through the temperature sensor, the temperature variable in the environment can be controlled to cope with the situation where the wavelength change caused by the temperature change leads to inaccurate cable force monitoring.

[0068] The above technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0069] Embodiment 1

[0070] A fiber grating axial force sensor, as Figure 1 shown, includes a stress tube and a metallized grating fixed in the stress tube;

[0071] Among them, the preparation steps of the metallized grating include:

[0072] Remove the coating layer on the surface of the optical fiber, then scratch the diffraction grating, and coat the transition metal on the surface of the optical fiber and the grating area to obtain a pre-treated optical fiber grating;

[0073] Weld a section of metal tube at both ends of the pre-treated optical fiber grating through glass solder to obtain the metallized grating;

[0074] Weld and fix the metallized grating in the stress tube through the metal tubes at both ends of the metallized grating;

[0075] The fiber grating axial force sensor further includes an adapter, a housing and a wire pin. One end of the adapter is connected to the stress tube, and the other end is connected to the housing. The adapter and the housing can conduct the axial force, and the wire pin is fixed in the housing;

[0076] The fiber Bragg grating axial force sensor further includes a circlip and a retaining ring. The wire pin is connected to the circlip and axially limited by the circlip. The retaining ring is welded and fixed on the housing to limit the circlip inside the housing.

[0077] The fiber Bragg grating axial force sensor further includes a connector. By threadedly connecting the connector to an electrical connector, the fiber Bragg grating axial force sensor is fixedly installed in the electrical connector. A schematic diagram of the fiber Bragg grating axial force sensor assembled in the electrical connector is shown in Figure 2 the figure (only one sensor is installed in the schematic diagram).

[0078] Embodiment 2

[0079] A method for monitoring the force on a cable based on a fiber Bragg grating axial force sensor includes the following steps:

[0080] Use a fiber optic sensing analyzer to monitor the force on the cable to be measured in real time. The fiber optic sensing analyzer has 32 channels. Among them, 4 fiber Bragg grating axial force sensors are provided in 31 channels, and a one-to-six splitter is used in the other channel. In addition to 4 fiber Bragg grating axial force sensors, 1 temperature sensor is also provided to control the temperature variable in the environment.

[0081] Install multiple fiber Bragg grating axial force sensors in the electrical connector and dock them with the cable to be measured.

[0082] Apply weights to the electrical connector, start the fiber optic sensing analyzer, apply different magnitudes of force to the electrical connector by changing the weight of the weights, so that the stress tube senses stress and undergoes strain elongation, and simultaneously stretch the metallized grating, causing the wavelength of the metallized grating to increase. Obtain the wavelength increase amount of the metallized grating through the fiber optic sensing analyzer.

[0083] Based on the wavelength increase amount, perform axial force calibration through the fiber Bragg grating axial force sensor to establish the relationship coefficient between the wavelength increase amount and strain.

[0084] Based on the relationship coefficient between the wavelength increase amount and strain, obtain the force parameter value of the cable to be measured.

[0085] Specifically, in this embodiment, the inner diameter of the stress tube is φ0.9mm and the outer diameter is φ1.4mm. By calculating its effective cross-sectional area to be 0.90mm 2 , the axial force of the fiber Bragg grating axial force sensor is designed to be 100N. Therefore, the stress σ of the stress tube under the action of a full load of 100N is:

[0086]

[0087] Since the yield strength σ0.2 of the stainless steel is ≥ 205 MPa (indicating that this stress tube can withstand the stress under the action of a full load of 100 N), and the elastic modulus E is 194 GPa;

[0088] It can be obtained that the strain ε at the stress tube is:

[0089]

[0090] It can meet the requirement of causing a large micro-strain deformation of the structure under the action of a full load of 100 N, that is, the measurement of the axial force of the pin by the fiber Bragg grating can be realized.

[0091] Specifically, the test results of the cables to be measured at different positions after being subjected to tension are shown in Table 1 below, and the force trend diagram of the cables to be measured displayed in the fiber optic sensing analyzer is as Figure 3 shown.

[0092] Table 1

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099] In summary, by using the monitoring method of this application, the stress condition of the cable can be fed back to the fiber Bragg grating axial force sensor. The fiber Bragg grating axial force sensor conducts its force to the stress tube. When the stress tube undergoes strain elongation, the metallized grating will be stretched synchronously, causing an increase in the grating wavelength. The stretching amount and the wavelength increase amount show a linear relationship. By calibrating the axial force of the fiber Bragg grating axial force sensor, the corresponding relationship coefficient can be obtained to monitor the real-time stress condition inside the cable conductor.

[0100] The above are only optional embodiments of this application, and do not limit the patent scope of this application accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of this application under the inventive concept of this application, or any direct / indirect application in other related technical fields is included in the patent protection scope of this application.

Claims

1. A cable stress monitoring method based on a fiber Bragg grating axial force sensor, characterized in that, Use an optical fiber sensing analyzer to monitor the force on the cable to be measured in real time. An optical fiber grating axial force sensor is provided in the channel of the optical fiber sensing analyzer. The optical fiber grating axial force sensor includes a stress tube and a metallized grating fixed in the stress tube. The method includes the following steps: Install the optical fiber grating axial force sensor in the electrical connector and dock it with the cable to be measured. Apply an axial force to the cable to be measured to cause the stress tube to strain, and obtain the wavelength increase of the metallized grating. Based on the wavelength increase, perform axial force calibration through the optical fiber grating axial force sensor to establish the relationship coefficient between the wavelength increase and strain. Based on the relationship coefficient between the wavelength increase and strain, obtain the force parameter value of the cable to be measured and form a force trend diagram of the cable to be measured for display in the optical fiber sensing analyzer.

2. The cable stress monitoring method based on the fiber Bragg grating axial force sensor according to claim 1, characterized in that The preparation steps of the metallized grating include: Remove the coating layer on the surface of the optical fiber, then scratch a diffraction grating, and coat a transition metal on the surface and grating area of the optical fiber to obtain a pre-treated optical fiber grating. Weld a metal tube at both ends of the pre-treated optical fiber grating through glass solder to obtain the metallized grating.

3. The cable stress monitoring method based on the fiber grating axial force sensor according to claim 2, characterized in that, The metallized grating is fixed in the stress tube by welding the metal tubes at both ends.

4. The cable force monitoring method based on the fiber Bragg grating axial force sensor according to claim 1, wherein, The optical fiber grating axial force sensor further includes an adapter, a housing, and a wire pin. One end of the adapter is connected to the stress tube, and the other end is connected to the housing. The adapter and the housing can conduct axial force, and the wire pin is fixed in the housing.

5. The cable stress monitoring method based on the fiber Bragg grating axial force sensor according to claim 4, wherein, The optical fiber grating axial force sensor further includes a circlip and a retaining ring. The wire pin is connected to the circlip and axially limited by the circlip. The retaining ring is welded and fixed to the housing to limit the circlip inside the housing.

6. The cable stress monitoring method based on the fiber Bragg grating axial force sensor according to claim 1, characterized in that, The optical fiber grating axial force sensor further includes a connector. The step of installing the optical fiber grating axial force sensor in the electrical connector includes: Threadedly connect with the electrical connector through the connector to fixedly install the optical fiber grating axial force sensor in the electrical connector.

7. The cable stress monitoring method based on the fiber Bragg grating axial force sensor according to claim 1, wherein The step of applying an axial force to the cable to be measured to cause the stress tube to strain and obtain the wavelength increase of the metallized grating includes: Apply weights to the electrical connector, start the optical fiber sensing analyzer, apply different magnitudes of force to the electrical connector by changing the weight of the weights, cause the stress tube to sense stress and strain and elongate, and simultaneously stretch the metallized grating to increase the wavelength of the metallized grating, and obtain the wavelength increase of the metallized grating through the optical fiber sensing analyzer.

8. The cable stress monitoring method based on the fiber Bragg grating axial force sensor according to claim 1, characterized in that, The optical fiber sensing analyzer has 32 channels.

9. The cable force monitoring method based on the fiber Bragg grating axial force sensor according to claim 8, characterized in that, A plurality of the optical fiber grating axial force sensors are provided in each channel of the optical fiber sensing analyzer.

10. The cable force monitoring method based on the fiber Bragg grating axial force sensor according to claim 8, characterized in that, At least one temperature sensor is further provided in one of the channels of the optical fiber sensing analyzer.

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