Cable fire prevention monitoring system and method based on distributed optical fiber sensing

Abstract

This invention relates to the field of cable monitoring technology, specifically disclosing a cable fire monitoring system and method based on distributed optical fiber sensing. The distributed optical fiber sensing unit is attached to the cable or its surroundings, simultaneously collecting temperature, vibration, and smoke signals and converting them into optical signals. After signal demodulation processing, an intelligent early warning and positioning unit, combined with algorithms, diagnoses the status and accurately locates the cable. A coordinated response unit automatically executes alarm, fire extinguishing, and power-off operations, while a remote monitoring unit enables multi-terminal visual control. This invention overcomes the limitations of single-parameter monitoring, offering high monitoring accuracy and fast response, effectively reducing false alarms and missed alarms. It is adaptable to various complex environments, possesses advantages such as high stability, low maintenance costs, and no need for on-site supervision, and can be widely applied to various cable fire monitoring scenarios to achieve early detection and early handling of potential hazards.

Description

Technical Field

[0001] This invention relates to the field of cable monitoring technology, specifically to a cable fire monitoring system and method based on distributed optical fiber sensing. Background Technology

[0002] As the core carrier of power and signal transmission, the operational safety of cables directly affects the stability of the power system, the normal operation of industrial production, and the safety of personnel and property. In actual operation, cables are highly susceptible to localized overheating due to factors such as overload, insulation aging, poor contact, external damage, high ambient temperatures, and debris accumulation. If not detected and addressed promptly, this overheating can spread rapidly, forming a fire that burns the cable lines, causing widespread power outages, equipment damage, and even fire accidents, resulting in severe economic losses and safety hazards.

[0003] Currently, existing cable fire monitoring technologies are mainly divided into two categories: traditional monitoring and sensor monitoring. Traditional monitoring technologies include manual inspection and temperature monitoring instrument spot checks, which suffer from low monitoring efficiency, poor real-time performance, numerous blind spots, high labor costs, and the inability to achieve all-weather monitoring. They often only detect fires after they occur and cannot provide early warnings. Existing sensor monitoring technologies mainly include point temperature sensor monitoring, infrared temperature measurement monitoring, and ordinary fiber optic sensor monitoring. Among these, point temperature sensor monitoring can only achieve single-point monitoring and cannot achieve continuous monitoring of the entire cable area, thus limiting monitoring coverage. Limited coverage and problems such as complex wiring, weak resistance to electromagnetic interference, and susceptibility to false alarms due to environmental interference; infrared temperature measurement monitoring is greatly affected by environmental dust, fog, and obstructions, resulting in low monitoring accuracy and unsuitability for enclosed and dimly lit environments such as cable trenches and cable tunnels; ordinary fiber optic sensing monitoring technology generally suffers from bottlenecks such as low spatial resolution, insufficient fire location accuracy, high false alarm rate, and poor environmental adaptability. Especially under complex working conditions, it is difficult to accurately distinguish between normal cable heating and fire hazards, and it cannot achieve multi-parameter collaborative monitoring, making it difficult to comprehensively assess the fire safety status of cables.

[0004] Furthermore, existing fiber optic sensing-based cable monitoring technologies and patents mostly focus on monitoring a single temperature parameter, or employ traditional demodulation algorithms that make it difficult to balance monitoring accuracy and response speed. They fail to achieve collaborative sensing and intelligent fusion diagnosis of multiple parameters such as temperature, vibration, and smoke, and exhibit significant shortcomings in anti-interference design, hazard classification and early warning, and rapid fire response, thus failing to meet the high-precision, high-reliability, and real-time requirements of cable fire monitoring in various scenarios. Therefore, developing a distributed fiber optic sensing cable fire monitoring system and method capable of continuous monitoring of the entire cable area, collaborative sensing of multiple parameters, high-precision positioning, low false alarm rate, rapid response, and autonomous handling capabilities has become an urgent technical problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a cable fire monitoring system and method based on distributed optical fiber sensing. Through innovative sensor structure design, multi-parameter collaborative sensing mechanism, intelligent demodulation algorithm and linkage response module, it can realize continuous monitoring of the entire cable area, early warning of fire hazards, accurate fire location, and rapid linkage response, reduce false alarm rate and missed alarm rate, improve the reliability and intelligence level of cable fire monitoring, and ensure the safe operation of cables.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a cable fire monitoring system based on distributed optical fiber sensing, including a distributed optical fiber sensing unit, a signal demodulation and processing unit, an intelligent early warning and positioning unit, a linkage response unit, a power supply unit and a remote monitoring unit; The distributed optical fiber sensing unit is a global continuous sensing structure that is attached to the cable surface or laid around the cable. It is used to collect temperature signals, vibration signals and smoke sensing signals during the operation of the cable, convert the physical signals into optical signals and transmit them to the signal demodulation and processing unit. The signal demodulation and processing unit is used to receive the optical signal transmitted by the distributed optical fiber sensing unit, demodulate it into an electrical signal, and perform preprocessing, fusion analysis, and screening of effective monitoring data. The intelligent early warning and positioning unit is used to store monitoring data, compare thresholds, intelligently diagnose the fire protection status of cables, accurately locate potential hazards or fires, and output early warning information. The linkage response unit is used to receive the warning or alarm signal from the intelligent warning and positioning unit, and to perform local alarm, fire extinguishing activation and cable power control operations. The power supply unit is used to provide a stable power supply; The remote monitoring unit is used for the remote transmission, viewing, storage, and remote management of monitoring data and early warning information, and can be accessed synchronously by multiple terminals.

[0007] Furthermore, the distributed optical fiber sensing unit includes a sensing optical fiber, a smoke-sensing coating, and a fixing component; the surface of the sensing optical fiber is coated with a smoke-sensing coating, which changes its refractive index when in contact with smoke, thereby altering the optical transmission characteristics of the sensing optical fiber; the fixing component includes a high-temperature resistant adhesive layer, an elastic clamping component, and a protective shell, the high-temperature resistant adhesive layer is used to initially adhere the sensing optical fiber to the cable surface, the elastic clamping component is used to tightly clamp the sensing optical fiber to the cable surface, and the protective shell is fitted over the outside of the sensing optical fiber.

[0008] Furthermore, the special optical fiber has a high temperature resistance range of -40℃ to 200℃ and a tensile strength of not less than 1500MPa; the smoke-sensing coating is made of polyimide substrate and nano-tin oxide dopant, the mass fraction of nano-tin oxide dopant is 5% to 12%, the thickness of the smoke-sensing coating is 50μm to 150μm, and the refractive index change within 3s to 8s after contact with smoke is not less than 0.002.

[0009] Furthermore, the signal demodulation and processing unit includes an optical demodulation module, a signal preprocessing module, and a data fusion module. The optical demodulation module employs an improved progressive differential demodulation algorithm. This algorithm optimizes the spatial resolution and error accuracy of optical signal demodulation by introducing an adaptive step size adjustment factor, ensuring that the temperature demodulation error is ≤ ±0.5℃, the vibration demodulation error is ≤ ±0.1g, and the smoke refractive index change demodulation error is ≤ ±0.0005. The signal preprocessing module uses a composite processing method combining Kalman filtering and wavelet denoising. The filtering frequency range is 10Hz~1000Hz, and the signal amplification factor is adaptively adjusted between 10x and 100x to eliminate invalid signals caused by environmental temperature fluctuations and external mechanical interference. The data fusion module employs a weighted fusion algorithm, assigning weights based on the confidence levels of the three types of signals: temperature, vibration, and smoke. The weight for temperature signals is 0.4~0.5, the weight for vibration signals is 0.2~0.3, and the weight for smoke signals is 0.2~0.3. The fused effective monitoring data is obtained through weighted calculation.

[0010] Furthermore, the intelligent early warning and positioning unit includes a data storage module, a threshold comparison module, an intelligent diagnosis module, and a positioning module. The data storage module uses dual backup storage with SSD solid-state drives and the cloud, supporting long-term storage and rapid retrieval of monitoring data, cable parameters, threshold standards, and historical data. The threshold comparison module presets three levels of thresholds: normal operation threshold, hidden danger early warning threshold, and fire alarm threshold. These three levels of thresholds are adaptively adjusted according to cable type, service life, and laying environment. The intelligent diagnosis module embeds a BP neural network machine learning algorithm, which intelligently identifies fire prevention status by training sample data of four states: normal cable operation, minor hidden danger, serious hidden danger, and fire. The positioning module uses optical time-domain reflectometry combined with phase analysis technology to accurately output the specific location, extension range, and development trend of hidden dangers or fires.

[0011] Furthermore, the intelligent early warning and positioning unit also includes an early warning level classification module, which classifies the early warning into three levels based on the threshold comparison results and intelligent diagnostic conclusions: Level 1 early warning corresponds to minor hidden dangers and outputs suggestive early warning information; Level 2 early warning corresponds to serious hidden dangers, outputs emergency early warning information and triggers local linkage; Level 3 early warning corresponds to fire, outputs the highest level alarm information and triggers system-wide linkage, and pushes it to remote terminals.

[0012] Furthermore, the linkage response unit includes a local alarm module, a fire extinguishing activation module, and a cable control module. The local alarm module includes an audible and visual alarm and a voice prompt. The audible and visual alarm has an alarm volume ≥85dB, and the alarm light brightness ≥500lux. The voice prompt continuously plays information about the location of the hazard and the handling instructions. The fire extinguishing activation module is linked with a preset fire extinguishing device and adaptively selects between spray fire extinguishing, dry powder fire extinguishing, or inert gas fire extinguishing according to the location and size of the fire. The cable control module is connected to the cable switchgear via a relay and automatically sends a trip control signal to cut off the cable power supply to the hazard area or fire area. At the same time, it feeds back the power cut-off status to each unit to prevent the fire from spreading.

[0013] Furthermore, the power supply unit includes a main power supply module, a backup power supply module, and a power management module; the main power supply module is powered by AC220V mains power; the backup power supply module uses a high-capacity lithium battery pack and has four protection functions: charging, discharging, overcharging, over-discharging, overcurrent, and short circuit; the power management module uses an intelligent switching chip to monitor the operating status of the main power supply and the backup power supply in real time, and automatically switches to the backup power supply when the main power supply fails or is interrupted.

[0014] Furthermore, the remote monitoring unit includes a communication module, a remote terminal, and a cloud platform. The communication module can select 5G, Ethernet, or fiber optic communication methods depending on the laying environment. The remote terminal includes a computer terminal and a mobile APP, supporting monitoring data viewing, early warning information reception, location information query, coordinated handling operations, and system parameter settings. The cloud platform has data statistical analysis, trend prediction, report generation, and access control functions. It can predict the development trend of cable fire hazards based on historical monitoring data, automatically generate daily, weekly, and monthly monitoring reports, support simultaneous access from multiple terminals, and realize remote visual control of cable fire monitoring.

[0015] This invention also provides a cable fire monitoring method based on distributed optical fiber sensing, comprising the following steps: Step 1: Continuous sensing and data acquisition across the entire area. A distributed optical fiber sensing structure is used to attach to the cable surface or lay around the cable to simultaneously acquire temperature signals, vibration signals and smoke detection signals during the cable's operation, and convert the physical signals into optical signals for transmission to the signal processing end. Step 2: Photoelectric demodulation and data preprocessing. The optical signal is received and demodulated into an electrical signal. A composite denoising process is used to remove invalid signals caused by environmental interference. Then, a weighted fusion algorithm is used to fuse and analyze the three types of electrical signals: temperature, vibration, and smoke, and the effective monitoring data is obtained by filtering. Step 3: Intelligent early warning and precise positioning. The effective monitoring data is stored and combined with the preset adaptive three-level threshold. The fire protection status of the cable is intelligently diagnosed through machine learning algorithms. At the same time, optical time domain reflectance combined with phase analysis technology is used to accurately locate the specific location, extension range and development trend of hidden dangers or fires. Based on the diagnosis results, the corresponding level of early warning or alarm information is output. Step 4: Joint response and stable power supply. Upon receiving the warning or alarm information, automatically execute local audible and visual alarms, voice prompts, corresponding fire extinguishing activation, and power cut-off operations for cables in areas with hidden dangers or fires. The entire process adopts a main and backup power intelligent switching mode to provide stable power supply. Step 5: Remote visual management and control. The monitoring data, early warning information and handling status are transmitted to the cloud platform and multiple terminals through communication methods adapted to the laying environment, so as to realize remote viewing, storage, statistical analysis, trend prediction and remote system management and control, and support simultaneous access from multiple terminals.

[0016] The advantages of this invention compared to the prior art are: This invention employs distributed fiber optic sensing units to achieve continuous monitoring of the entire cable area. It combines multi-parameter collaborative sensing of temperature, vibration, and smoke to overcome the limitations of existing single-parameter monitoring. It innovatively adopts an improved progressive differential decomposition and adjustment algorithm to enhance monitoring accuracy and spatial resolution. Temperature monitoring accuracy is ≤ ±0.5℃, and positioning accuracy is ≤ 5cm, solving the problems of low accuracy and numerous blind spots in traditional monitoring.

[0017] This invention uses a weighted fusion analysis of the data fusion module to eliminate environmental interference data; combined with a BP neural network intelligent diagnostic algorithm, it accurately distinguishes between normal cable heating and various hidden dangers and fires, with a diagnostic accuracy of ≥99%, effectively reducing false alarm rate and missed alarm rate, and solving the industry pain point of high false alarm rate in existing systems.

[0018] The smoke-sensing coating of the sensing fiber of the present invention has a response time of ≤0.5s, a demodulation response time of ≤0.1s, and an overall system response time of ≤1s; the linkage and handling unit realizes hierarchical linkage, which can automatically start alarm, power-off and fire extinguishing measures without manual intervention, quickly control the spread of fire and minimize losses.

[0019] The sensing optical fiber of this invention is a special optical fiber that is resistant to high temperature, corrosion and tension. The smoke sensing coating is made of inorganic nanomaterials and is suitable for various environments from -40℃ to 200℃. It is resistant to electromagnetic interference, dust and fog, and can be widely used in various complex scenarios such as cable trenches, cable tunnels, outdoor areas and high-rise buildings.

[0020] This invention combines a cloud platform with remote terminals to achieve real-time transmission, cloud storage, and trend analysis of monitoring data. Staff can view and control the data remotely without on-site supervision, reducing labor costs. It also supports simultaneous access from multiple terminals and generates automated monitoring reports, facilitating routine management of cable fire prevention and fault tracing.

[0021] The distributed optical fiber sensing unit of this invention adopts an integrated fixed design, which can be laid close to the cable surface without complex wiring; the service life of the sensing optical fiber and the smoke sensing coating is ≥10 years; the power supply unit has backup power and protection functions; the overall system has high stability, low maintenance cost, and is easy to promote and apply on a large scale. Attached Figure Description

[0022] Figure 1 This is a system block diagram of the cable fire monitoring system based on distributed optical fiber sensing of the present invention.

[0023] Figure 2 This is a flowchart of the cable fire monitoring method based on distributed optical fiber sensing according to the present invention. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0025] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0026] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0027] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0028] The cable fire monitoring system and method based on distributed optical fiber sensing of the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] Combined with appendix Figure 1-2 This invention will be described in detail below.

[0030] A cable fire monitoring system based on distributed optical fiber sensing includes a distributed optical fiber sensing unit, a signal demodulation and processing unit, an intelligent early warning and positioning unit, a linkage response unit, a power supply unit, and a remote monitoring unit. The units are connected to each other via wired or wireless communication to form a closed-loop monitoring and response system. The distributed optical fiber sensing unit is a continuous sensing structure covering the entire area. It is attached to the cable surface or laid around the cable to collect temperature signals, vibration signals, and smoke detection signals during cable operation. It converts the physical signals into optical signals and transmits them to the signal demodulation and processing unit. The distributed optical fiber sensing unit includes a sensing optical fiber, a smoke detection coating, and a fixing component. The sensing optical fiber is a special optical fiber that is resistant to high temperature, corrosion, and tensile strength. Its surface is coated with a smoke detection coating. The smoke detection coating changes its refractive index when exposed to smoke, thereby changing the light transmission characteristics of the sensing optical fiber. The fixing component is used to tightly attach the sensing optical fiber to the cable surface and fix it to ensure sensing stability. The signal demodulation and processing unit includes an optical demodulation module, a signal preprocessing module, and a data fusion module. The optical demodulation module receives the optical signal transmitted by the distributed optical fiber sensing unit and uses an improved progressive differential demodulation algorithm to demodulate the optical signal into electrical signals corresponding to temperature, vibration, and smoke, solving the problems of low spatial resolution and large error in traditional demodulation algorithms. The signal preprocessing module filters, amplifies, and denoises the demodulated electrical signal to remove environmental interference signals. The data fusion module performs collaborative fusion analysis on the preprocessed temperature, vibration, and smoke electrical signals, and, combined with cable operating parameter thresholds, filters out valid monitoring data and removes invalid interference data to improve data accuracy. The intelligent early warning and positioning unit includes a data storage module, a threshold comparison module, an intelligent diagnosis module, and a positioning module. The data storage module stores monitoring data, cable parameters, threshold standards, and historical data. The threshold comparison module compares the valid monitoring data output by the data fusion module with preset thresholds, including normal operation thresholds, hazard warning thresholds, and fire alarm thresholds, with different thresholds corresponding to different warning levels. The intelligent diagnosis module combines monitoring data, historical data, and cable operating status to intelligently diagnose the cable's fire protection status using machine learning algorithms, distinguishing between normal overheating, minor hazards, serious hazards, and fires, thus reducing false alarm rates. The positioning module uses optical time-domain reflectometry combined with phase analysis technology to accurately locate the specific location of hazards or fires based on the optical transmission time difference and refractive index change of the sensing fiber, achieving a positioning accuracy of centimeter-level. The coordinated response unit includes a local alarm module, a fire extinguishing activation module, and a cable control module. The local alarm module is used to issue an audible and visual alarm signal to alert on-site personnel when a warning or alarm threshold is triggered. The fire extinguishing activation module is used to automatically activate preset fire extinguishing devices, including sprinkler fire extinguishing, dry powder fire extinguishing, or inert gas fire extinguishing, when a fire alarm threshold is triggered, to quickly control the spread of the fire. The cable control module is used to automatically send a control signal to the cable switchgear to cut off the cable power supply in the hazard area or fire area when a serious hazard or fire alarm threshold is triggered, to prevent the fire from spreading. The power supply unit includes a main power supply module, a backup power supply module, and a power management module. The main power supply module is powered by mains power, and the backup power supply module is powered by a lithium battery pack with charging, discharging, and overcharge / over-discharge protection functions. The power management module is used to control the switching between the main power supply and the backup power supply to ensure that the system can still operate normally when the mains power is interrupted, thus ensuring continuous monitoring. The remote monitoring unit includes a communication module, a remote terminal, and a cloud platform. The communication module uses 5G, Ethernet, or fiber optic communication to transmit monitoring data, early warning information, and location information from the intelligent early warning and positioning unit to the remote terminal and cloud platform. The remote terminal includes a computer terminal and a mobile APP, which are used by staff to remotely view monitoring data, receive early warning information, and control the linkage response unit. The cloud platform is used for cloud storage, data analysis, trend prediction of monitoring data, and generation of monitoring reports. It supports simultaneous access from multiple terminals to achieve remote management and control of cable fire prevention monitoring.

[0031] As a further optimization of the present invention, the sensing optical fiber adopts a polarization-maintaining special optical fiber with a core diameter of 8-10 μm, a cladding diameter of 125 μm, an operating wavelength of 1550 nm, a high temperature resistance range of -40℃ to 200℃, and a tensile strength ≥1500 MPa, ensuring sensing stability and service life in complex environments; the smoke sensing coating adopts an inorganic nano-coating, mainly composed of titanium dioxide and tin oxide, with a thickness of 5-10 μm. When it comes into contact with particulate matter or harmful gases in smoke, the refractive index change is ≥0.001, and the response time is ≤0.5s, ensuring rapid sensing and transmission of smoke signals.

[0032] As a further optimization of the present invention, the improved progressive differential demodulation algorithm is based on a single long pulse excitation of a Brillouin scattering signal. Through stepwise forward differential and iterative step size optimization, combined with the signal characteristics of the cable monitoring scenario, the peak value of the differential gain curve is extracted and corrected. This solves the problems of large error and complex demodulation in small-sized events by the traditional progressive differential demodulation algorithm, making the temperature monitoring accuracy ≤ ±0.5℃, the vibration monitoring accuracy ≤ ±0.1g, the spatial resolution ≤ 5cm, and the demodulation response time ≤ 0.1s.

[0033] As a further optimization of the present invention, the data fusion module adopts a weighted fusion algorithm, assigning different weight coefficients according to the importance of three types of signals: temperature, vibration, and smoke. The weight of the temperature signal is 0.5, the weight of the vibration signal is 0.2, and the weight of the smoke signal is 0.3. The comprehensive monitoring value is obtained through weighted calculation, and the weight coefficients are dynamically adjusted in combination with the cable operating status to ensure the rationality and accuracy of data fusion. The intelligent diagnosis module adopts a BP neural network algorithm, which learns from training samples to achieve accurate diagnosis of six states of the cable, including normal operation, overload heating, insulation aging, poor contact, external collision, and fire, with a diagnostic accuracy rate of ≥99%.

[0034] As a further optimization of the present invention, the positioning module combines optical time domain reflectance (OTDR) technology and phase-sensitive optical time domain reflectance (φ-OTDR) technology. By measuring the transmission time, reflection intensity and phase change of the optical signal in the sensing fiber, and combining the laying length and location information of the sensing fiber, the module can accurately calculate the specific location of the hidden danger or fire with a positioning error of ≤5cm. At the same time, it can display the cable number, laying location and surrounding environment information of the hidden danger area, which can facilitate the rapid handling by the staff.

[0035] As a further optimization of the present invention, the linkage response unit can realize hierarchical linkage. When the monitoring data reaches the threshold for minor hidden dangers, only the local audible and visual alarm is activated; when the threshold for serious hidden dangers is reached, the local audible and visual alarm and partial power cut-off of the cable are activated; when the fire alarm threshold is reached, the local audible and visual alarm, complete power cut-off, fire extinguishing device and remote alarm are activated to ensure the targeted and timely response. The fire extinguishing device can automatically select the fire extinguishing method according to the cable laying scenario (cable trench, cable tunnel, indoor distribution cabinet) to avoid equipment damage caused by accidental activation.

[0036] As a further optimization of the present invention, the power management module has an intelligent monitoring function, which can monitor the voltage and current status of the main power supply and the backup power supply in real time. When the mains power is interrupted or the voltage is abnormal, it automatically switches to the backup power supply with a switching time of ≤0.1s. The backup power supply has a battery life of ≥72h, supports solar-assisted charging, and is suitable for outdoor scenarios without mains power. It also has overcharge, over-discharge, and short-circuit protection functions to extend the service life of the backup power supply.

[0037] As a further optimization of the present invention, the cloud platform of the remote monitoring unit has data statistics, trend analysis, and fault tracing functions, and can automatically generate daily, weekly, and monthly monitoring reports, displaying cable temperature change trends, frequency of potential hazards, and handling status; it supports multi-user permission management, allowing users with different permissions to view monitoring data and operation permissions within different ranges; the mobile APP supports pushing early warning information and remotely controlling the linkage handling unit, with a response time of ≤1s, ensuring that staff can promptly grasp the monitoring situation.

[0038] Based on the above system, the present invention further provides a cable fire monitoring method based on distributed optical fiber sensing, comprising the following steps: Step 1: Continuous sensing and data acquisition across the entire area. A distributed optical fiber sensing structure is used to attach to the cable surface or lay around the cable to simultaneously acquire temperature signals, vibration signals and smoke detection signals during the cable's operation, and convert the physical signals into optical signals for transmission to the signal processing end. Step 2: Photoelectric demodulation and data preprocessing. The optical signal is received and demodulated into an electrical signal. A composite denoising process is used to remove invalid signals caused by environmental interference. Then, a weighted fusion algorithm is used to fuse and analyze the three types of electrical signals: temperature, vibration, and smoke, and the effective monitoring data is obtained by filtering. Step 3: Intelligent early warning and precise positioning. The effective monitoring data is stored and combined with the preset adaptive three-level threshold. The fire protection status of the cable is intelligently diagnosed through machine learning algorithms. At the same time, optical time domain reflectance combined with phase analysis technology is used to accurately locate the specific location, extension range and development trend of hidden dangers or fires. Based on the diagnosis results, the corresponding level of early warning or alarm information is output. Step 4: Joint response and stable power supply. Upon receiving the warning or alarm information, automatically execute local audible and visual alarms, voice prompts, corresponding fire extinguishing activation, and power cut-off operations for cables in areas with hidden dangers or fires. The entire process adopts a main and backup power intelligent switching mode to provide stable power supply. Step 5: Remote visual management and control. The monitoring data, early warning information and handling status are transmitted to the cloud platform and multiple terminals through communication methods adapted to the laying environment, so as to realize remote viewing, storage, statistical analysis, trend prediction and remote system management and control, and support simultaneous access from multiple terminals.

[0039] The specific implementation process of the cable fire monitoring system and method based on distributed optical fiber sensing of this invention is as follows: System startup: The power supply unit starts working, the main power supply supplies power to each unit, the power management module monitors the power status, and the backup power supply is in standby mode; the distributed fiber optic sensing unit attaches to the cable surface, completes initialization, and enters real-time sensing mode. Signal Acquisition: The sensing fiber of the distributed optical fiber sensing unit collects the temperature and vibration signals of the cable in real time. When smoke comes into contact with the cable, the refractive index of the smoke sensing coating changes. The sensing fiber converts the three physical signals of temperature, vibration and smoke into optical signals and continuously transmits them to the signal demodulation and processing unit. Signal processing: The optical demodulation module uses an improved progressive differential demodulation algorithm to demodulate the optical signal into the corresponding electrical signal; the signal preprocessing module filters, amplifies, and denoises the electrical signal to remove environmental interference; the data fusion module uses a weighted fusion algorithm to fuse and analyze the three types of electrical signals and output effective monitoring data. Intelligent Diagnosis and Location: The threshold comparison module of the intelligent early warning and location unit compares the effective monitoring data with the preset threshold to determine the cable's operating status; the intelligent diagnosis module uses a BP neural network algorithm to accurately diagnose the fault type; the location module combines OTDR and φ-OTDR technologies to accurately locate potential hazards or fires. Early warning and coordinated response: Based on the diagnostic results and threshold levels, the intelligent early warning and positioning unit issues corresponding early warning signals, and the coordinated response unit initiates graded response measures (audible and visual alarms, power outages, and fire extinguishing); at the same time, the communication module transmits monitoring data, early warning information, and positioning information to remote terminals and cloud platforms; Remote control and follow-up: Staff can view relevant information and remotely control the linkage response unit through remote terminals or mobile APP; the cloud platform stores monitoring data, generates monitoring reports, and performs trend analysis; after the hazard or fire is dealt with, the staff resets the system, restores the cable to normal operation, and the system continues to enter real-time monitoring state; Power switching: When the mains power is interrupted, the power management module automatically switches to the backup power supply to ensure continuous system monitoring; after the mains power is restored, it automatically switches back to the main power supply and charges the backup power supply. The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A cable fire monitoring system based on distributed optical fiber sensing, characterized in that: It includes a distributed optical fiber sensing unit, a signal demodulation and processing unit, an intelligent early warning and positioning unit, a linkage and response unit, a power supply unit, and a remote monitoring unit; The distributed optical fiber sensing unit is a global continuous sensing structure that is attached to the cable surface or laid around the cable. It is used to collect temperature signals, vibration signals and smoke sensing signals during the operation of the cable, convert the physical signals into optical signals and transmit them to the signal demodulation and processing unit. The signal demodulation and processing unit is used to receive the optical signal transmitted by the distributed optical fiber sensing unit, demodulate it into an electrical signal, and perform preprocessing, fusion analysis, and screening of effective monitoring data. The intelligent early warning and positioning unit is used to store monitoring data, compare thresholds, intelligently diagnose the fire protection status of cables, accurately locate potential hazards or fires, and output early warning information. The linkage response unit is used to receive the warning or alarm signal from the intelligent warning and positioning unit, and to perform local alarm, fire extinguishing activation and cable power control operations. The power supply unit is used to provide a stable power supply; The remote monitoring unit is used for the remote transmission, viewing, storage, and remote management of monitoring data and early warning information, and can be accessed synchronously by multiple terminals.

2. The cable fire monitoring system based on distributed optical fiber sensing according to claim 1, characterized in that: The distributed optical fiber sensing unit includes a sensing optical fiber, a smoke-sensing coating, and a fixing component. The surface of the sensing optical fiber is coated with a smoke-sensing coating, which changes its refractive index when in contact with smoke, thereby altering the optical transmission characteristics of the sensing optical fiber. The fixing component includes a high-temperature resistant adhesive layer, an elastic clamping component, and a protective shell. The high-temperature resistant adhesive layer is used to initially adhere the sensing optical fiber to the cable surface, the elastic clamping component is used to tightly press the sensing optical fiber onto the cable surface, and the protective shell is fitted over the outside of the sensing optical fiber.

3. The cable fire monitoring system based on distributed optical fiber sensing according to claim 2, characterized in that: The special optical fiber has a high temperature resistance range of -40℃ to 200℃ and a tensile strength of not less than 1500MPa; the smoke sensing coating is made of polyimide substrate and nano tin oxide dopant, the mass fraction of nano tin oxide dopant is 5% to 12%, the thickness of the smoke sensing coating is 50μm to 150μm, and the refractive index change within 3s to 8s after contact with smoke is not less than 0.

002.

4. The cable fire monitoring system based on distributed optical fiber sensing according to claim 3, characterized in that: The signal demodulation and processing unit includes an optical demodulation module, a signal preprocessing module, and a data fusion module. The optical demodulation module employs an improved progressive differential demodulation algorithm. This algorithm optimizes the spatial resolution and error accuracy of optical signal demodulation by introducing an adaptive step size adjustment factor, ensuring that the temperature demodulation error is ≤ ±0.5℃, the vibration demodulation error is ≤ ±0.1g, and the smoke refractive index change demodulation error is ≤ ±0.0005. The signal preprocessing module uses a composite processing method combining Kalman filtering and wavelet denoising. The filtering frequency range is 10Hz~1000Hz, and the signal amplification factor is adaptively adjusted between 10x and 100x to remove invalid signals caused by environmental temperature fluctuations and external mechanical interference. The data fusion module uses a weighted fusion algorithm, assigning weights based on the confidence levels of the three types of signals: temperature, vibration, and smoke. The weight for temperature signals is 0.4~0.5, the weight for vibration signals is 0.2~0.3, and the weight for smoke signals is 0.2~0.

3. The fused effective monitoring data is obtained through weighted calculation.

5. The cable fire monitoring system based on distributed optical fiber sensing according to claim 4, characterized in that: The intelligent early warning and positioning unit includes a data storage module, a threshold comparison module, an intelligent diagnosis module, and a positioning module. The data storage module uses dual backup storage of SSD solid-state drive and cloud, supporting long-term storage and fast retrieval of monitoring data, cable parameters, threshold standards, and historical data. The threshold comparison module presets three levels of thresholds, namely normal operation threshold, hidden danger early warning threshold, and fire alarm threshold. The three levels of thresholds are adaptively adjusted according to cable type, service life, and laying environment. The intelligent diagnostic module embeds a BP neural network machine learning algorithm, which performs intelligent identification of fire prevention status by training sample data of four states: normal cable operation, minor hidden danger, serious hidden danger, and fire. The positioning module uses optical time domain reflectance combined with phase analysis technology to accurately output the specific location, extension range, and development trend of hidden dangers or fires.

6. The cable fire monitoring system based on distributed optical fiber sensing according to claim 5, characterized in that: The intelligent early warning and positioning unit also includes an early warning level classification module, which classifies the early warning into three levels based on the threshold comparison results and intelligent diagnostic conclusions: Level 1 early warning corresponds to minor hidden dangers and outputs suggestive early warning information; Level 2 warning corresponds to serious hidden dangers, outputs emergency warning information and triggers local linkage; Level 3 warning corresponds to fire, outputs the highest level alarm information and triggers system-wide linkage, and pushes it to remote terminals.

7. The cable fire monitoring system based on distributed optical fiber sensing according to claim 6, characterized in that: The linkage response unit includes a local alarm module, a fire extinguishing activation module, and a cable control module. The local alarm module includes an audible and visual alarm and a voice prompt. The audible and visual alarm has an alarm volume of ≥85dB and an alarm light brightness of ≥500lux. The voice prompt continuously plays information about the location of the hazard and instructions for handling it. The fire extinguishing activation module is linked with a preset fire extinguishing device and adaptively selects between spray fire extinguishing, dry powder fire extinguishing, or inert gas fire extinguishing method according to the location and size of the fire. The cable control module is connected to the cable switchgear via a relay, automatically sending a trip control signal to cut off the cable power supply to the hazard area or fire area, and simultaneously feeding back the power cut-off status to each unit to prevent the fire from spreading.

8. The cable fire monitoring system based on distributed optical fiber sensing according to claim 7, characterized in that: The power supply unit includes a main power module, a backup power module, and a power management module. The main power module is powered by AC220V mains power. The backup power module uses a high-capacity lithium battery pack and has four protection functions: charging, discharging, overcharging, over-discharging, overcurrent, and short circuit protection. The power management module uses an intelligent switching chip to monitor the operating status of the main power and backup power in real time. When the main power fails or is interrupted, it automatically switches to the backup power supply.

9. The cable fire monitoring system based on distributed optical fiber sensing according to claim 8, characterized in that: The remote monitoring unit includes a communication module, a remote terminal, and a cloud platform. The communication module can select 5G, Ethernet, or fiber optic communication methods depending on the laying environment. The remote terminal includes a computer terminal and a mobile APP, supporting monitoring data viewing, early warning information reception, location information query, coordinated response operations, and system parameter settings. The cloud platform has data statistical analysis, trend prediction, report generation, and access control functions. It can predict the development trend of cable fire hazards based on historical monitoring data, automatically generate daily, weekly, and monthly monitoring reports, support simultaneous access from multiple terminals, and realize remote visual control of cable fire monitoring.

10. A cable fire monitoring method based on distributed optical fiber sensing, characterized in that: Includes the following steps: Step 1: Continuous sensing and data acquisition across the entire area. A distributed optical fiber sensing structure is used to attach to the cable surface or lay around the cable to simultaneously acquire temperature signals, vibration signals and smoke detection signals during the cable's operation, and convert the physical signals into optical signals for transmission to the signal processing end. Step 2: Photoelectric demodulation and data preprocessing. The optical signal is received and demodulated into an electrical signal. A composite denoising process is used to remove invalid signals caused by environmental interference. Then, a weighted fusion algorithm is used to fuse and analyze the three types of electrical signals: temperature, vibration, and smoke, and the effective monitoring data is obtained by filtering. Step 3: Intelligent early warning and precise positioning. The effective monitoring data is stored and combined with the preset adaptive three-level threshold. The fire protection status of the cable is intelligently diagnosed through machine learning algorithms. At the same time, optical time domain reflectance combined with phase analysis technology is used to accurately locate the specific location, extension range and development trend of hidden dangers or fires. Based on the diagnosis results, the corresponding level of early warning or alarm information is output. Step 4: Joint response and stable power supply. Upon receiving the warning or alarm information, automatically execute local audible and visual alarms, voice prompts, corresponding fire extinguishing activation, and power cut-off operations for cables in areas with hidden dangers or fires. The entire process adopts a main and backup power intelligent switching mode to provide stable power supply. Step 5: Remote visual management and control. The monitoring data, early warning information and handling status are transmitted to the cloud platform and multiple terminals through communication methods adapted to the laying environment, so as to realize remote viewing, storage, statistical analysis, trend prediction and remote system management and control, and support simultaneous access from multiple terminals.

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