System and method for monitoring cable damage of coal mining machine based on optical fiber distributed sensing

Abstract

The invention relates to the technical field of concealed project acceptance, and discloses a cable damage monitoring system and method based on optical fiber distributed sensing for a coal mining machine, and the system employs an optical fiber composite coal mining machine cable as a sensing unit, combines DAS and OFDR technologies, and achieves the high-precision and high-efficiency monitoring and positioning of the cable fault of the coal mining machine. The system is mainly composed of an optical fiber composite coal mining machine cable, a DAS host, an OFDR host, a data processing server and a service monitoring terminal. Abnormal discharge sound signals and abnormal deformation signals of the cable are collected through the sensing optical fiber and are processed and demodulated by the DAS host and the OFDR host respectively, and finally the accurate position of the cable insulation fault is determined. The system has the beneficial effects of improving the monitoring precision and efficiency, enhancing the stability and reliability of the system, reducing the operation and maintenance cost, improving the safety production level of a coal mine and promoting the intelligent development of the coal mine.

Description

Technical Field

[0001] The present invention relates to the field of cable damage monitoring, and in particular to a system and method for monitoring cable damage of a coal mining machine based on optical fiber distributed sensing. Background Art

[0002] As coal mine production increases, remote-controlled shearers are increasingly used underground. Shearer cables are primarily responsible for providing power and transmitting control signals to the shearers, ensuring their proper operation. However, due to increasing electrical loads and mechanical fatigue, shearer cables often suffer sheath damage or even internal wire breakage due to impacts and scrapes from gangue or large coal lumps, leading to cable failures.

[0003] Currently, the commonly used bridge method and low-voltage pulse reflection method are suitable for low-resistance and open-circuit faults, but are not suitable for high-resistance and flashover faults. While the high-voltage pulse current method can handle high-resistance and flashover faults, it requires high-voltage equipment and is complex to operate. Ultrasonic and infrared thermal imaging monitoring methods, while effective, are significantly affected by the environment and have low accuracy in underground coal mines. Therefore, a system and method are needed that can accurately and efficiently monitor and locate coal mining machine cable faults. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a cable damage monitoring system and method for coal mining machines based on optical fiber distributed sensing to solve the problems existing in the prior art.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A shearer cable damage monitoring system based on optical fiber distributed sensing includes: an optical fiber composite shearer cable, an optical fiber distributed acoustic wave sensing host, an optical fiber distributed optical frequency domain reflectometry host, a data processing server, and a service monitoring terminal;

[0007] The optical fiber composite shearer cable has a sensing optical fiber unit added to the gap of the inherent four-core structure in the center of the shearer cable. The sensing optical fiber unit is composed of a G652D single-mode sensing optical fiber, a silicone-based fiber paste filled in the tube, and a thin-walled seamless stainless steel tube. The outer diameter of the thin-walled stainless steel tube is tangent to the outer diameter of the four-core cable structure, which can resist damage caused by external mechanical forces.

[0008] The optical fiber distributed acoustic sensor host is used to monitor the abnormal discharge sound signal of the coal mining machine cable and transmit the signal light to the DAS host to demodulate the abnormal discharge position information;

[0009] The fiber distributed optical frequency domain reflectometer host is used to monitor the abnormal deformation position of the coal mining machine cable and transmit the signal light to the OFDR host to demodulate the abnormal strain position information;

[0010] The data processing server is used to process the information provided by the DAS host and the OFDR host to determine the precise location of the cable insulation fault;

[0011] The service monitoring terminal is used to display fault location and status information in real time.

[0012] Preferably, the design of the optical fiber composite coal mining machine cable enables the sensing optical fiber unit to sense external sound waves and strain, specifically including:

[0013] Power line core conductor, power line core insulation, metal braided shielding layer in parallel with ground wire, ground wire, control line conductor, control line insulation, control line covering layer, and sheath;

[0014] Increase the cross-sectional area of the metal braided layer outside the power line core and the control line core, or place a bare conductor in the gap between the power line cores to ensure that the parallel resistance of the ground wire meets the requirements of the relevant standards.

[0015] Preferably, the DAS host realizes monitoring and demodulation of abnormal discharge sound by the following methods:

[0016] The distributed measurement and restoration of acoustic wave signals are achieved by utilizing the phase change of the backscattered Rayleigh light of the light transmitted in the optical fiber;

[0017] When an optical fiber is affected by external vibrations / acoustic waves, according to Hooke's law and the optical-elastic effect of the optical fiber, the length and refractive index of the optical fiber change, causing the optical path of the transmitted light wave to change, which in turn affects the phase of the backscattered Rayleigh light.

[0018] By using a fiber optic interferometer to interfere with the disturbed and undisturbed backscattered light, the distribution of the phase change of the interference light is calculated and extracted, and the position of the phase change peak is found to achieve monitoring and positioning of external disturbance events.

[0019] Preferably, the OFDR host realizes monitoring and demodulation of abnormal deformation by the following methods:

[0020] Using a linearly tunable light source, the light wave is split into two beams, one of which is injected into the reference arm as the reference light, and the other is injected into the fiber under test (FUT) as the probe light;

[0021] The backscattered Rayleigh signal and the reference signal beat each other on the detector, and the Rayleigh scattering information at different positions is demodulated through spectrum analysis.

[0022] Since backward Rayleigh scattering is caused by random fluctuations in the fiber's refractive index, OFDR can be compared to a random static long-period weak fiber Bragg grating. Changes in physical quantities such as temperature and stress at a certain position along the fiber to be measured can cause the grating period at the corresponding position to change, thereby shifting the backward Rayleigh scattering.

[0023] Using the cross-correlation method, the original beat frequency signal and the beat frequency signal after stress application or temperature change are cross-correlated, and distributed temperature or strain sensing is achieved by analyzing the offset after cross-correlation.

[0024] Preferably, the data processing server comprehensively processes the information provided by the DAS host and the OFDR host using the following algorithm:

[0025] Calculate the phase change of the fiber interferometer:

[0026] Where Δφ is the phase change, n is the fiber refractive index, L is the fiber length, λ0 is the wavelength of the light, and ΔL is the change in fiber length.

[0027] Preferably, the difference frequency component of the heterodyne detection method is calculated as: f best =|f1-f2|;

[0028] Where, f beat is the difference frequency component, f1 is the signal light frequency, and f2 is the reference light frequency.

[0029] Preferably, the beat signal frequency of the OFDR system is calculated as:

[0030] Where, f beat is the beat signal frequency, v is the speed of light, and λ is the wavelength of the light wave.

[0031] Better, cross-correlation method offset calculation:

[0032] Where Offset is the offset, S(t) is the original beat signal, R(t) is the beat signal after stress is applied or temperature is changed, and τ is the time delay.

[0033] Preferably, the service monitoring terminal displays the fault location and status information in real time so that operation and maintenance personnel can take repair measures in a timely manner.

[0034] A method for monitoring cable damage in a coal mining machine based on optical fiber distributed sensing includes the following steps:

[0035] Lay and install the fiber-optic composite coal mining machine cable according to the design requirements and connect it to the DAS and OFDR monitoring host;

[0036] Debug and calibrate the system to ensure that all parts are firmly connected and signal transmission is normal;

[0037] When the shearer cable is running, the sensing optical fiber acts as an acoustic wave sensor and together with the DAS host constitutes a cable abnormal discharge acoustic wave sensing system to collect abnormal discharge sound signals of the cable in real time;

[0038] At the same time, the sensing fiber acts as a strain sensor and together with the OFDR host constitutes a cable strain sensing system, which collects in real time abnormal deformation signals of the cable caused by coal gangue, large coal blocks falling and being hit, or foreign objects squeezing in the cable trough;

[0039] The DAS host processes the collected abnormal discharge sound signals and uses the phase change of the backward Rayleigh scattered light of the light transmitted in the optical fiber to achieve distributed measurement and restoration of the acoustic wave signals;

[0040] The fiber optic interferometer is used to interfere with the disturbed and undisturbed backscattered light, calculate and extract the distribution of the phase change of the interference light, find the position of the phase change peak, and demodulate the abnormal discharge position information;

[0041] The OFDR host processes the collected abnormal deformation signal and uses a linearly tuned light source to split the light wave into two beams. One beam is injected into the reference arm as the reference light, and the other beam is injected into the fiber under test (FUT) as the detection light.

[0042] The backscattered Rayleigh signal and the reference signal beat each other on the detector, and the Rayleigh scattering information at different positions is demodulated through spectrum analysis.

[0043] Using the cross-correlation method, the original beat frequency signal and the beat frequency signal after stress application or temperature change are cross-correlated. By analyzing the offset after cross-correlation, the abnormal strain position information is demodulated;

[0044] The data processing server integrates the information provided by the DAS host and the OFDR host, and uses algorithms to calculate the phase change of the fiber interferometer, the difference frequency component of the heterodyne detection method, the beat signal frequency of the OFDR system, and the offset of the cross-correlation method;

[0045] Through these calculation results, the precise location of the cable insulation fault is determined;

[0046] The business monitoring terminal displays the fault location and status information in real time, so that operation and maintenance personnel can take timely repair measures.

[0047] In summary, the present invention mainly has the following beneficial effects:

[0048] 1. The present invention adopts fiber optic distributed sensing technology, combined with DAS and OFDR technology, to achieve high-precision and high-efficiency monitoring of coal mining machine cable faults. Compared with the traditional bridge method, low-voltage pulse reflection method, high-voltage pulse current method, ultrasonic monitoring and infrared thermal imaging monitoring method, fiber optic distributed sensing technology can more accurately locate the fault position, improving the accuracy and reliability of monitoring; the DAS host and OFDR host respectively collect and demodulate the abnormal discharge sound and abnormal deformation signal in real time, and through comprehensive processing by the data processing server, the precise location of the cable insulation fault can be quickly determined, greatly improving the efficiency of fault location; the design of the fiber optic composite coal mining machine cable enables the sensing fiber unit to effectively resist damage caused by external mechanical forces and protect the integrity of the optical fiber. The outer diameter of the thin-walled stainless steel pipe is tangent to the outer diameter of the four-core cable structure, which can effectively transmit sound pressure and strain to the sensing optical fiber, improving the stability and reliability of the system; the system uses the cross-correlation method to achieve distributed temperature or strain sensing. This method has high accuracy and stability and can accurately monitor the operating status of the cable in complex environments.

[0049] 2. The system and method provided by the present invention can monitor the operating status of the coal mining machine cable in real time, detect and locate faults in time, and reduce the downtime and maintenance costs caused by cable faults; the optical fiber distributed sensing technology does not require high-voltage equipment and professionals to perform complex operations, which reduces the difficulty and cost of system operation and maintenance. At the same time, the system has a long service life, low maintenance cost, and good economic benefits; the application of the present invention can monitor the operating status of the coal mining machine cable in real time, detect and handle cable faults in time, avoid safety accidents caused by cable faults, and improve the safety production level of coal mines; the system provides a function of real-time display of fault location and status information, which facilitates operation and maintenance personnel to take maintenance measures in time to ensure the continuity and safety of coal mine production; the present invention is based on advanced optical fiber distributed sensing technology, realizes intelligent monitoring and positioning of coal mining machine cable damage, and provides strong support for the intelligent development of coal mines; the system can be integrated with other intelligent equipment and systems to realize comprehensive monitoring and intelligent management of coal mine production processes, and promote the transformation of the coal mining industry to intelligence and digitalization. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a flow chart of the system of the present invention;

[0051] Figure 2 It is a schematic diagram of the structure of the optical fiber composite coal mining machine cable.

[0052] In the figure: 1. Power line core conductor; 2. Power line core insulation; 3. Metal braided shield layer in parallel with ground wire; 4. Ground wire; 5. Control line conductor; 6. Control line insulation; 7. Control line covering layer; 8. Sheath. DETAILED DESCRIPTION

[0053] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Example 1

[0055] refer to Figure 1-2 , a shearer cable damage monitoring system based on optical fiber distributed sensing, comprising:

[0056] Fiber-optic composite coal mining machine cable, fiber-optic distributed acoustic wave sensor host, fiber-optic distributed optical frequency domain reflectometer host, data processing server, business monitoring terminal;

[0057] The optical fiber composite shearer cable has a sensing optical fiber unit added to the gap of the inherent four-core structure in the center of the shearer cable. The sensing optical fiber unit is composed of a G652D single-mode sensing optical fiber, a silicone-based fiber paste filled in the tube, and a thin-walled seamless stainless steel tube. The outer diameter of the thin-walled stainless steel tube is tangent to the outer diameter of the four-core cable structure, which can resist damage caused by external mechanical forces.

[0058] The optical fiber distributed acoustic sensor host is used to monitor the abnormal discharge sound signal of the coal mining machine cable and transmit the signal light to the DAS host to demodulate the abnormal discharge position information;

[0059] The fiber distributed optical frequency domain reflectometer host is used to monitor the abnormal deformation position of the coal mining machine cable and transmit the signal light to the OFDR host to demodulate the abnormal strain position information;

[0060] The data processing server is used to process the information provided by the DAS host and the OFDR host to determine the precise location of the cable insulation fault;

[0061] The service monitoring terminal is used to display fault location and status information in real time.

[0062] The design of the optical fiber composite shearer cable enables the sensing optical fiber unit to sense external sound waves and strain, specifically including:

[0063] Power line core conductor 1, power line core insulation 2, metal braided shield layer in parallel with ground wire 3, ground wire 4, control line conductor 5, control line insulation 6, control line covering layer 7, sheath 8;

[0064] Increase the cross-sectional area of the metal braided layer outside the power line core and the control line core, or place a bare conductor in the gap between the power line cores to ensure that the parallel resistance of the ground wire meets the requirements of the relevant standards.

[0065] The DAS host monitors and demodulates abnormal discharge sounds in the following ways:

[0066] The distributed measurement and restoration of acoustic wave signals are achieved by utilizing the phase change of the backscattered Rayleigh light of the light transmitted in the optical fiber;

[0067] When an optical fiber is affected by external vibrations / acoustic waves, according to Hooke's law and the optical-elastic effect of the optical fiber, the length and refractive index of the optical fiber change, causing the optical path of the transmitted light wave to change, which in turn affects the phase of the backscattered Rayleigh light.

[0068] By using a fiber optic interferometer to interfere with the disturbed and undisturbed backscattered light, the distribution of the phase change of the interference light is calculated and extracted, and the position of the phase change peak is found to achieve monitoring and positioning of external disturbance events.

[0069] The OFDR host monitors and demodulates abnormal deformations in the following ways:

[0070] Using a linearly tunable light source, the light wave is split into two beams, one of which is injected into the reference arm as the reference light, and the other is injected into the fiber under test (FUT) as the probe light;

[0071] The backscattered Rayleigh signal and the reference signal beat each other on the detector, and the Rayleigh scattering information at different positions is demodulated through spectrum analysis.

[0072] Since backward Rayleigh scattering is caused by random fluctuations in the fiber's refractive index, OFDR can be compared to a random static long-period weak fiber Bragg grating. Changes in physical quantities such as temperature and stress at a certain position along the fiber to be measured can cause the grating period at the corresponding position to change, thereby shifting the backward Rayleigh scattering.

[0073] Using the cross-correlation method, the original beat frequency signal and the beat frequency signal after stress application or temperature change are cross-correlated, and distributed temperature or strain sensing is achieved by analyzing the offset after cross-correlation.

[0074] The data processing server comprehensively processes the information provided by the DAS host and the OFDR host through the following algorithm:

[0075] Calculate the phase change of the fiber interferometer:

[0076] Where Δφ is the phase change, n is the fiber refractive index, L is the fiber length, λ0 is the wavelength of the light wave, and ΔL is the change in fiber length;

[0077] Calculation of beat signal frequency of OFDR system:

[0078] Where, f beatis the beat signal frequency, v is the speed of light, and λ is the wavelength of the light wave;

[0079] Offset calculation using the cross-correlation method:

[0080] Where Offset is the offset, S(t) is the original beat signal, R(t) is the beat signal after stress is applied or temperature is changed, and τ is the time delay;

[0081] The service monitoring terminal displays the fault location and status information in real time so that operation and maintenance personnel can take repair measures in a timely manner.

[0082] A method for monitoring cable damage in a coal mining machine based on optical fiber distributed sensing includes the following steps:

[0083] Lay and install the fiber-optic composite coal mining machine cable according to the design requirements and connect it to the DAS and OFDR monitoring host;

[0084] Debug and calibrate the system to ensure that all parts are firmly connected and signal transmission is normal;

[0085] When the shearer cable is running, the sensing optical fiber acts as an acoustic wave sensor and together with the DAS host constitutes a cable abnormal discharge acoustic wave sensing system to collect abnormal discharge sound signals of the cable in real time;

[0086] At the same time, the sensing fiber acts as a strain sensor and together with the OFDR host constitutes a cable strain sensing system, which collects in real time abnormal deformation signals of the cable caused by coal gangue, large coal blocks falling and being hit, or foreign objects squeezing in the cable trough;

[0087] The DAS host processes the collected abnormal discharge sound signals and uses the phase change of the backward Rayleigh scattered light of the light transmitted in the optical fiber to achieve distributed measurement and restoration of the acoustic wave signals;

[0088] The fiber optic interferometer is used to interfere with the disturbed and undisturbed backscattered light, calculate and extract the distribution of the phase change of the interference light, find the position of the phase change peak, and demodulate the abnormal discharge position information;

[0089] The OFDR host processes the collected abnormal deformation signal and uses a linearly tuned light source to split the light wave into two beams. One beam is injected into the reference arm as the reference light, and the other beam is injected into the fiber under test (FUT) as the detection light.

[0090] The backscattered Rayleigh signal and the reference signal beat each other on the detector, and the Rayleigh scattering information at different positions is demodulated through spectrum analysis.

[0091] Using the cross-correlation method, the original beat frequency signal and the beat frequency signal after stress application or temperature change are cross-correlated. By analyzing the offset after cross-correlation, the abnormal strain position information is demodulated;

[0092] The data processing server integrates the information provided by the DAS host and the OFDR host, and uses algorithms to calculate the phase change of the fiber interferometer, the difference frequency component of the heterodyne detection method, the beat signal frequency of the OFDR system, and the offset of the cross-correlation method;

[0093] Through these calculation results, the precise location of the cable insulation fault is determined;

[0094] The business monitoring terminal displays the fault location and status information in real time, so that operation and maintenance personnel can take timely repair measures.

[0095] Example 2

[0096] A fiber-optic composite shearer cable was designed based on the actual use of shearer cables. A sensing fiber unit was added to the gap within the inherent four-core structure at the center of the shearer cable. This sensing fiber unit consists of a G652D single-mode sensing fiber, a silicone-based fiber paste filled tube, and a thin-walled seamless stainless steel tube. The outer diameter of the thin-walled stainless steel tube is tangent to the outer diameter of the four-core cable structure, effectively resisting damage caused by external mechanical forces. The designed fiber-optic composite shearer cable was installed according to the actual installation requirements of the coal mine. Ensure that the cable is laid neatly and securely to avoid signal loss or misjudgment due to looseness or twisting. Simultaneously, the sensing fiber was connected to the DAS and OFDR monitoring host for system debugging and calibration.

[0097] Example 3

[0098] During coal mining machine cable operation, the optical fiber sensor, acting as an acoustic sensor, works with the DAS host to form a cable abnormal discharge acoustic wave sensing system, collecting abnormal discharge acoustic signals in real time. Simultaneously, the optical fiber sensor, acting as a strain sensor, works with the OFDR host to form a cable strain sensing system, collecting real-time signals of abnormal cable deformation caused by falling gangue, large coal blocks, or foreign objects in the cable trough. The DAS host processes the collected abnormal discharge acoustic signals, utilizing the phase shift of Rayleigh backscattered light transmitted through the optical fiber to achieve distributed measurement and restoration of the acoustic signal. A fiber interferometer interferes with the disturbed and undisturbed backscattered light, calculates and extracts the distribution of the phase shift of the interference light, locates the phase shift peak, and demodulates the abnormal discharge location information. The OFDR host processes the collected abnormal deformation signals, using a linearly tuned light source to split the light wave into two beams. One beam is injected into the reference arm as the reference light, and the other beam is injected into the fiber under test (FUT) as the probe light. The backscattered Rayleigh signal beats with the reference signal at the detector. Spectral analysis is used to demodulate Rayleigh scattering information at different locations. Using the cross-correlation method, the original beat signal is cross-correlated with the beat signal after stress or temperature change. By analyzing the offset after cross-correlation, the location of the abnormal strain is demodulated. The data processing server integrates information provided by the DAS host and the OFDR host, using an algorithm to calculate the phase change of the fiber interferometer, the difference frequency component of the heterodyne detection method, the beat signal frequency of the OFDR system, and the offset of the cross-correlation method. These calculation results determine the precise location of the cable insulation fault. The service monitoring terminal displays the fault location and status in real time, allowing maintenance personnel to take timely repair measures. The system also records information such as the time, location, and type of fault, providing a basis for subsequent fault analysis and prevention.

[0099] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A cable damage monitoring system for coal mining machines based on optical fiber distributed sensing, characterized in that: Including: optical fiber composite coal mining machine cable, optical fiber distributed acoustic wave sensor host, optical fiber distributed optical frequency domain reflectometer host, data processing server, business monitoring terminal; The optical fiber composite shearer cable has a sensing optical fiber unit added to the gap of the inherent four-core structure in the center of the shearer cable. The sensing optical fiber unit is composed of a G652D single-mode sensing optical fiber, a silicone-based fiber paste filled in the tube, and a thin-walled seamless stainless steel tube. The outer diameter of the thin-walled stainless steel tube is tangent to the outer diameter of the four-core cable structure, which can resist damage caused by external mechanical forces. The optical fiber distributed acoustic sensor host is used to monitor the abnormal discharge sound signal of the coal mining machine cable and transmit the signal light to the DAS host to demodulate the abnormal discharge position information; The fiber distributed optical frequency domain reflectometer host is used to monitor the abnormal deformation position of the coal mining machine cable and transmit the signal light to the OFDR host to demodulate the abnormal strain position information; The data processing server is used to process the information provided by the DAS host and the OFDR host to determine the precise location of the cable insulation fault; The service monitoring terminal is used to display fault location and status information in real time.

2. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 1 is characterized in that: The design of the optical fiber composite shearer cable enables the sensing optical fiber unit to sense external sound waves and strain, specifically including: Power line core conductor (1), power line core insulation (2), metal braided shielding layer connected in parallel with a ground wire (3), a ground wire (4), a control line conductor (5), a control line insulation (6), a control line covering layer (7), and a sheath (8); Increase the cross-sectional area of the metal braided layer outside the power line core and the control line core, or place a bare conductor in the gap between the power line cores to ensure that the parallel resistance of the ground wire meets the requirements of the relevant standards.

3. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 2 is characterized in that: The DAS host monitors and demodulates abnormal discharge sounds in the following ways: The distributed measurement and restoration of acoustic wave signals are achieved by utilizing the phase change of the backscattered Rayleigh light of the light transmitted in the optical fiber; When an optical fiber is affected by external vibrations / acoustic waves, according to Hooke's law and the optical-elastic effect of the optical fiber, the length and refractive index of the optical fiber change, causing the optical path of the transmitted light wave to change, which in turn affects the phase of the backscattered Rayleigh light. By using a fiber optic interferometer to interfere with the disturbed and undisturbed backscattered light, the distribution of the phase change of the interference light is calculated and extracted, and the position of the phase change peak is found to achieve monitoring and positioning of external disturbance events.

4. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 3 is characterized in that: The OFDR host monitors and demodulates abnormal deformations in the following ways: Using a linearly tunable light source, the light wave is split into two beams, one of which is injected into the reference arm as the reference light, and the other is injected into the fiber under test (FUT) as the probe light; The backscattered Rayleigh signal and the reference signal beat each other on the detector, and the Rayleigh scattering information at different positions is demodulated through spectrum analysis. Since backward Rayleigh scattering is caused by random fluctuations in the fiber's refractive index, OFDR can be compared to a random static long-period weak fiber Bragg grating. Changes in physical quantities such as temperature and stress at a certain position along the fiber to be measured can cause the grating period at the corresponding position to change, thereby shifting the backward Rayleigh scattering. Using the cross-correlation method, the original beat frequency signal and the beat frequency signal after stress application or temperature change are cross-correlated, and distributed temperature or strain sensing is achieved by analyzing the offset after cross-correlation.

5. According to the optical fiber distributed sensing coal mining machine cable damage monitoring system of claim 4, the data processing server comprehensively processes the information provided by the DAS host and the OFDR host using the following algorithm: Calculate the phase change of the fiber interferometer: Where Δφ is the phase change, n is the fiber refractive index, L is the fiber length, λ0 is the wavelength of the light, and ΔL is the change in fiber length.

6. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 5 is characterized in that: Calculation of the difference frequency component of the heterodyne detection method: f beat =|f1-f2|; Where, f beat is the difference frequency component, f1 is the signal light frequency, and f2 is the reference light frequency.

7. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 6 is characterized in that: Calculation of beat signal frequency of OFDR system: Where, f beat is the beat signal frequency, v is the speed of light, and λ is the wavelength of the light wave.

8. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 7 is characterized in that: Offset calculation using the cross-correlation method: Where Offset is the offset, S(t) is the original beat signal, R(t) is the beat signal after stress is applied or temperature is changed, and τ is the time delay.

9. The cable damage monitoring system for coal mining machines based on optical fiber distributed sensing according to claim 1 is characterized in that: The service monitoring terminal displays the fault location and status information in real time so that operation and maintenance personnel can take repair measures in a timely manner.

10. A method for monitoring cable damage of a coal mining machine based on optical fiber distributed sensing according to any one of claims 1 to 9, characterized in that: The following steps are involved: Lay and install the fiber-optic composite coal mining machine cable according to the design requirements and connect it to the DAS and OFDR monitoring host; Debug and calibrate the system to ensure that all parts are firmly connected and signal transmission is normal; When the shearer cable is running, the sensing optical fiber acts as an acoustic wave sensor and together with the DAS host constitutes a cable abnormal discharge acoustic wave sensing system to collect abnormal discharge sound signals of the cable in real time; At the same time, the sensing fiber acts as a strain sensor and together with the OFDR host constitutes a cable strain sensing system, which collects in real time abnormal deformation signals of the cable caused by coal gangue, large coal blocks falling and being hit, or foreign objects squeezing in the cable trough; The DAS host processes the collected abnormal discharge sound signals and uses the phase change of the backward Rayleigh scattered light of the light transmitted in the optical fiber to achieve distributed measurement and restoration of the acoustic wave signals; The fiber optic interferometer is used to interfere with the disturbed and undisturbed backscattered light, calculate and extract the distribution of the phase change of the interference light, find the position of the phase change peak, and demodulate the abnormal discharge position information; The OFDR host processes the collected abnormal deformation signal and uses a linearly tuned light source to split the light wave into two beams. One beam is injected into the reference arm as the reference light, and the other beam is injected into the fiber under test (FUT) as the detection light. The backscattered Rayleigh signal and the reference signal beat each other on the detector, and the Rayleigh scattering information at different positions is demodulated through spectrum analysis. Using the cross-correlation method, the original beat frequency signal and the beat frequency signal after stress application or temperature change are cross-correlated. By analyzing the offset after cross-correlation, the abnormal strain position information is demodulated; The data processing server integrates the information provided by the DAS host and the OFDR host, and uses algorithms to calculate the phase change of the fiber interferometer, the difference frequency component of the heterodyne detection method, the beat signal frequency of the OFDR system, and the offset of the cross-correlation method; Through these calculation results, the precise location of the cable insulation fault is determined; The business monitoring terminal displays the fault location and status information in real time, so that operation and maintenance personnel can take timely repair measures.

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