Distributed optical fiber temperature measurement system based on Raman scattering

Abstract

The invention relates to the field of optical fiber optics, in particular to a distributed optical fiber temperature measurement system based on Raman scattering, which comprises an optical signal excitation and separation module, a signal acquisition and preprocessing module, a temperature resolving module, a calibration and correction module, a real-time monitoring and early warning module and a management database, the system performs digital accumulation noise reduction on scattering signals through separation of Stokes light and anti-Stokes light, real-time monitoring of optical power and division of spatial positions, generates a temperature distribution curve through temperature calculation and determination of the spatial positions corresponding to the temperatures, generates calibration coefficients through selection of constant-temperature reference points and fitting of a temperature deviation curve, and performs calibration on the scattering signals. The temperature is corrected, a calibration curve is calibrated, meanwhile, light intensity attenuation is compensated, and the light temperature can be accurately measured and early warning can be carried out in time by setting multi-stage temperature early warning threshold values and monitoring temperature abnormal points.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber optics, and in particular to a distributed optical fiber temperature measurement system based on Raman scattering. Background Art

[0002] As digitalization and intelligentization sweep across industries, accurate temperature monitoring has become crucial for stable operations in many fields. In power systems, overheating cable connectors can cause fires, and poor heat dissipation in data center servers can affect data processing efficiency and equipment lifespan.

[0003] Distributed fiber optic temperature measurement uses optical fiber as the sensing unit and utilizes the scattering characteristics of light to achieve long-distance, continuous distributed temperature monitoring. It has unique advantages such as anti-electromagnetic interference, corrosion resistance, and embeddable installation. It can adapt to complex and harsh monitoring environments and provides innovative solutions for industrial safety monitoring, energy efficient management, infrastructure health diagnosis and other fields. It has become an important direction for the development of temperature monitoring technology and plays an increasingly important role in promoting the intelligent upgrading of various industries.

[0004] Although distributed fiber-optic temperature measurement technology has shown great application potential, existing technologies still have many problems that need to be solved. For example, the existing Chinese patent application number 201310017365.0 discloses a distributed fiber-optic Raman temperature measurement system. This solution enters the sensing fiber to be measured after passing through a wavelength division multiplexer. During the propagation of pulsed laser light in the fiber, it continuously generates backscattering. The backscattered light returns to the wavelength division multiplexer. After filtering by the wavelength division multiplexer, the Stokes Raman scattered light and anti-Stokes Raman scattered light are filtered out and enter the dual-channel avalanche photodiode for photoelectric conversion. The electrical signal output by the dual-channel avalanche photodiode is processed by a DSP digital signal processor to obtain a temperature signal. The processing speed is fast, and the real-time performance of the temperature measurement can be achieved without affecting the accuracy.

[0005] However, this solution has the following shortcomings: First, although this solution has cumulative processing and wavelet denoising, it lacks a systematic method for spatial position division, and cannot accurately determine the temperature corresponding position, which may miss the hidden danger of local overheating of the optical fiber.

[0006] Second, this solution only calculates the temperature through a fixed formula, without considering the dynamic factors of optical fiber characteristics changing with time and environment. It also lacks a mechanism to update the parameters of the temperature calculation model, and errors will continue to accumulate over long-term use.

[0007] 3. The plan does not mention a complete early warning mechanism and only relies on temperature calculation results. It lacks multi-dimensional abnormality judgment standards and graded early warning functions. It cannot detect temperature anomalies in a timely and accurate manner, and it is difficult to effectively ensure the safety of the monitored objects in practical applications. Summary of the Invention

[0008] In order to overcome the shortcomings of the background technology, an embodiment of the present invention provides a distributed optical fiber temperature measurement system based on Raman scattering, which can effectively solve the problems involved in the above background technology.

[0009] The objectives of the present invention can be achieved through the following technical solutions: The present invention provides a distributed optical fiber temperature measurement system based on Raman scattering, including: an optical signal excitation and separation module, which is used to separate Stokes light and anti-Stokes light through a splitter and a dual-wavelength optical filter, monitor the optical power in real time, and automatically adjust the laser output power.

[0010] The signal acquisition and preprocessing module is used to divide the spatial position based on the principle of optical time domain reflection, calculate the minimum accumulation number algorithm, and perform digital accumulation and noise reduction on the scattered signal.

[0011] The temperature calculation module is used to calculate the temperature through the intensity ratio of Stokes light and anti-Stokes light, determine the spatial position corresponding to the temperature using the principle of optical time domain reflectometry, and generate a temperature distribution curve.

[0012] The calibration correction module is used to select constant temperature reference points, fit the temperature deviation curve to generate calibration coefficients, correct the temperature and calibrate the calibration curve, and compensate for light intensity attenuation.

[0013] The real-time monitoring and early warning module is used to set multi-level temperature warning thresholds, monitor temperature anomalies, record abnormal information and trigger corresponding level early warning responses.

[0014] Management database, used to store optical fiber attenuation coefficient, constant temperature reference point temperature, temperature calibration curve, warning threshold, temperature-position mapping table and historical temperature data.

[0015] Preferably, the specific analysis method of the optical signal excitation and separation module is: injecting a laser pulse into the sensing optical fiber, preliminarily separating the backscattered light generated when the laser pulse propagates in the sensing optical fiber through a spectrometer, and further separating the Stokes light and the anti-Stokes light using a dual-wavelength optical filter.

[0016] The power of the separated Stokes light and anti-Stokes light is monitored. When the monitored optical power deviates from the set reasonable range of optical power, an alarm mechanism is triggered and the laser output power is automatically adjusted to compensate.

[0017] Preferably, the specific analysis method for dividing the spatial position is: pre-setting the segmentation parameters of the single measurement scattering signal, the segmentation parameters include the spatial position range corresponding to each data segment, and the spatial position range is determined based on the optical time domain reflection principle and combined with the sensing optical fiber length.

[0018] Based on the system noise characteristics and the target signal-to-noise ratio, the minimum number of accumulations required to meet the signal quality requirements is calculated. The optical pulse emission module is controlled to inject laser pulses into the sensing fiber to stimulate the generation of a scattering signal containing temperature information. The scattering signal is then transmitted to the digital accumulation unit for photoelectric conversion and digital processing.

[0019] The digitized scattered signal is segmented in the time domain, and each time window corresponds to a data segment. Each time window is converted into a specific spatial position area on the sensing optical fiber, and the segmented data segments are stored in the cache area of the corresponding spatial position according to the corresponding relationship.

[0020] Preferably, the specific analysis method of the minimum number of accumulations is: by measuring the system output in the absence of signal input, the white noise power spectrum density of the system is obtained, and at the same time, the operating bandwidth of the system and the absolute temperature of the system working environment are clarified. According to the temperature measurement accuracy requirements, the target signal-to-noise ratio is set, and it is converted from decibels to a linear value, which is then brought into the calculation formula of the minimum number of accumulations to obtain the minimum number of accumulations that meets the signal quality requirements.

[0021] Preferably, the specific analysis method for digital accumulation noise reduction of the scattered signal is: performing multiple measurements according to the minimum accumulation number, each measurement generates a scattered signal data segment corresponding to each spatial position and stores it in the corresponding buffer area, forming multiple groups of scattered signal data segmented by spatial position.

[0022] For the cache area at the same spatial position, the data segments corresponding to multiple measurements are extracted in turn, the values of the corresponding data points in the multiple measurement signals at the same spatial position are superimposed and summed, and the sum of the superimposed signals is divided by the number of measurements to obtain the mean data point at the spatial position.

[0023] Traverse the data segments of all spatial positions and generate a mean sequence containing the mean data points of each spatial position.

[0024] Preferably, the specific analysis method of the temperature corresponding to the spatial position is: from the mean sequence, respectively extracting the Stokes light signal intensity value and the anti-Stokes light signal intensity value corresponding to the same spatial position, calculating the ratio of the Stokes light intensity value to the anti-Stokes light intensity value, and obtaining the Raman scattering intensity ratio.

[0025] A preset temperature calibration curve is called, wherein the calibration curve is a mapping relationship between Raman scattering intensity ratio and temperature value, and the Raman scattering intensity ratio is substituted into the calibration curve to calculate the temperature value of the corresponding spatial position.

[0026] Preferably, the specific analysis method of the temperature solution module is: recording the starting time of the optical pulse emission module injecting the laser pulse into the sensing optical fiber, and at the same time detecting the receiving time of the scattered signal reaching the photoelectric conversion module, and calculating the time difference between the receiving time and the starting time.

[0027] The material refractive index parameters of the sensing optical fiber are obtained, and based on the principle of optical time domain reflection, the time difference is multiplied by the speed of light and divided by twice the material refractive index to calculate the spatial position distance corresponding to the scattering signal.

[0028] The spatial position distance is mapped to specific physical position coordinates on the sensing optical fiber, and a one-to-one correspondence between the temperature value and the physical position coordinates is established.

[0029] The temperature values of all spatial positions calculated within the same measurement cycle are associated with the corresponding physical position coordinates to generate a temperature-position mapping table. Based on the temperature-position mapping table, a continuous temperature distribution curve is generated with the physical position as the horizontal axis and the temperature value as the vertical axis.

[0030] Preferably, the specific analysis method of the calibration curve is: setting constant temperature reference points of known temperature at the starting end, middle section and end position of the sensing optical fiber respectively, and automatically collecting the standard temperature values of the constant temperature reference points according to the set time, and recording them as the standard temperature values of each constant temperature reference point at each time point.

[0031] The temperature deviation curve is formed by subtracting the standard temperature value of each constant temperature reference point at each time point from the corresponding temperature value on the temperature calibration curve. The temperature deviation curve is fitted to generate a calibration coefficient matrix. The calibration coefficient matrix is substituted into the temperature correction formula. The linear correction mode or the nonlinear correction mode is determined in real time according to the temperature fluctuation range, and the temperature calibration curve is recalibrated using the corrected temperature value.

[0032] Preferably, the specific analysis method for compensating for light intensity attenuation is: dividing the sensing optical fiber into several small segments of fixed length according to length, obtaining the initial attenuation coefficient of each segment of the sensing optical fiber from the management database, establishing a model for the change of the attenuation coefficient with temperature, and using the trapezoidal integration method to approximately calculate the cumulative attenuation from the starting end of the sensing optical fiber to a certain position on the sensing optical fiber. The compensation factor is calculated based on the attenuation, and the scattered light intensity at the position is compensated to obtain the final compensated light intensity, thereby correcting the correspondence between the temperature value and the light intensity.

[0033] Preferably, the specific analysis method of the real-time monitoring and early warning module is: set multiple levels of temperature early warning thresholds respectively, and when it is detected that the temperature at a certain position of the sensing optical fiber exceeds a certain level of early warning threshold, the position is judged as a temperature abnormality point, and the temperature value of the abnormal point and the time when the abnormality is detected are recorded.

[0034] Based on the calibrated and corrected temperature data, multi-level temperature warning thresholds are preset. The multi-level temperature warning thresholds include an absolute temperature threshold, a relative temperature threshold calculated based on historical temperature data, and a temperature change rate threshold. The absolute temperature threshold is used to set specific temperature values for different levels of warnings, the relative temperature threshold is calculated based on statistics such as the mean and standard deviation of historical temperature data, and the temperature change rate threshold is used to measure the amplitude of temperature change per unit time.

[0035] The temperature of each position of the sensing optical fiber is monitored in real time. When the temperature at a certain position meets any of the following conditions, the position is determined to be a temperature anomaly point: the temperature exceeds the absolute temperature threshold, the temperature exceeds the relative temperature threshold calculated based on historical temperature data, or the temperature change rate exceeds the set temperature change rate threshold.

[0036] After determining that a certain location is a temperature anomaly point, the temperature value of the anomaly point and the time when the anomaly is detected are recorded, and its specific physical position coordinates on the sensing optical fiber are obtained based on the temperature distribution curve. Different levels of warning responses are triggered based on the degree of deviation between the temperature value of the anomaly point and the preset multi-level temperature warning threshold.

[0037] Compared with the existing technology, the present invention has the following beneficial effects: First, the present invention separates Stokes light and anti-Stokes light and monitors the optical power in real time, which can accurately obtain the intensity information of the optical signal. By dividing the spatial position, the scattered signal is digitally accumulated and noise-reduced, which helps to accurately analyze the changes in light during transmission.

[0038] 2. The present invention calculates the temperature by the intensity ratio of Stokes light and anti-Stokes light, uses the principle of optical time-domain reflection to determine the spatial position corresponding to the temperature, generates a temperature distribution curve, achieves high-precision spatial positioning of the temperature distribution, and accurately knows the temperature conditions at different locations.

[0039] 3. The present invention selects constant temperature reference points, fits the temperature deviation curve to generate calibration coefficients, corrects the temperature and calibrates the calibration curve, and compensates for light intensity attenuation. It can eliminate the influence of light intensity changes caused by loss and other reasons when light is transmitted in the optical fiber on temperature measurement, thereby ensuring the stability of light intensity.

[0040] 4. The present invention sets multi-level temperature warning thresholds, monitors temperature anomalies, records anomaly information and triggers corresponding level warning responses, so that different response measures can be taken according to the severity of the anomaly. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 This is a system module connection diagram of the present invention.

[0043] Figure 2 for Figure 1 Flowchart of dividing spatial positions in the signal acquisition and preprocessing module.

[0044] Figure 3 for Figure 1 Flowchart of the temperature solution module. DETAILED DESCRIPTION

[0045] 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 any creative efforts shall fall within the scope of protection of the present invention.

[0046] See also Figure 1 As shown, a distributed optical fiber temperature measurement system based on Raman scattering includes an optical signal excitation and separation module, a signal acquisition and preprocessing module, a temperature solution module, a calibration and correction module, a real-time monitoring and early warning module, and a management database.

[0047] The management database is connected to the signal acquisition and preprocessing module, the temperature calculation module, the calibration correction module, and the real-time monitoring and early warning module; the temperature calculation module is connected to the signal acquisition and preprocessing module and the calibration correction module; the optical signal excitation and separation module is connected to the signal acquisition and preprocessing module; and the calibration correction module is connected to the real-time monitoring and early warning module.

[0048] The optical signal excitation and separation module is used to separate Stokes light and anti-Stokes light through a spectrometer and a dual-wavelength optical filter, monitor the optical power in real time, and automatically adjust the laser output power.

[0049] The specific analysis method of the optical signal excitation and separation module is as follows: a laser pulse is injected into the sensing fiber, backscattered light generated by the laser pulse propagating in the sensing fiber is initially separated by a spectrometer, and Stokes light and anti-Stokes light are further separated by a dual-wavelength optical filter. This module can accurately separate the required optical signal and ensure that the monitored optical power is within a reasonable range, thereby improving the system's processing accuracy and stability for the optical signal and providing a reliable optical signal foundation for subsequent accurate temperature measurement.

[0050] The power of the separated Stokes light and anti-Stokes light is monitored. When the monitored optical power deviates from the set optical power range, an alarm mechanism is triggered and the laser output power is automatically adjusted to compensate. This helps maintain optical power stability, ensures the accuracy and reliability of system measurements, and reduces measurement errors caused by optical power fluctuations.

[0051] The signal acquisition and preprocessing module is used to divide the spatial position based on the principle of optical time domain reflection, calculate the minimum accumulation number algorithm, and perform digital accumulation and noise reduction on the scattered signal.

[0052] See also Figure 2 As shown, the specific analysis method for dividing the spatial position is: pre-setting the segmentation parameters of the single measurement scattering signal, the segmentation parameters include the spatial position range corresponding to each data segment, and the spatial position range is determined based on the principle of optical time domain reflection and combined with the length of the sensing fiber; it can accurately divide the spatial position of the sensing fiber, providing a basis for the subsequent accurate acquisition of temperature information at different positions.

[0053] Based on the system noise characteristics and the target signal-to-noise ratio, the minimum number of accumulations required to meet signal quality requirements is calculated. The optical pulse emission module is controlled to inject laser pulses into the sensing fiber, generating a scattered signal containing temperature information. This scattered signal is then transmitted to a digital accumulation unit for photoelectric conversion and digital processing. By determining the appropriate number of accumulations, signal quality can be improved, noise interference can be reduced, and the system can more accurately collect and process scattered signals, thereby more precisely determining the temperature at each spatial location.

[0054] The digitized scattered signal is segmented in the time domain, and each time window corresponds to a data segment. Each time window is converted into a specific spatial position area on the sensing optical fiber, and the segmented data segments are stored in the cache area of the corresponding spatial position according to the corresponding relationship.

[0055] The specific analysis method for the minimum number of accumulations is as follows: by measuring the system output in the absence of signal input, the white noise power spectral density of the system is obtained, and at the same time, the operating bandwidth of the system and the absolute temperature of the system working environment are clarified. According to the temperature measurement accuracy requirements, the target signal-to-noise ratio is set, and it is converted from decibels to a linear value. This is then introduced into the calculation formula of the minimum number of accumulations to obtain the minimum number of accumulations that meets the signal quality requirements. The optimal number of measurements can be determined based on the system's own characteristics and actual needs, and the measurement process can be optimized to improve measurement efficiency while ensuring measurement accuracy, thereby avoiding waste of resources caused by unnecessary measurements.

[0056] It should be noted that the formula for converting the target signal-to-noise ratio from decibels to a linear value is: , substitute it into the formula Minimum accumulation times to meet signal quality requirements ,in represents the white noise power spectral density of the system, Indicates the absolute temperature of the system's working environment. is the working bandwidth of the system.

[0057] The specific analysis method for digital accumulation and noise reduction of the scattered signal is: performing multiple measurements according to the minimum accumulation number, each measurement generates a scattered signal data segment corresponding to each spatial position and stores it in the corresponding buffer area, forming multiple groups of scattered signal data segmented by spatial position.

[0058] For the cache area at the same spatial position, the data segments corresponding to multiple measurements are extracted in turn, the values of the corresponding data points in the multiple measurement signals at the same spatial position are superimposed and summed, and the sum of the superimposed signals is divided by the number of measurements to obtain the mean data point at the spatial position.

[0059] Traverse the data segments of all spatial positions and generate a mean sequence containing the mean data points of each spatial position; it can effectively reduce the noise in the scattered signal, improve the stability and accuracy of the signal by taking the average of multiple measurements, and make the measurement results more reliable.

[0060] The temperature calculation module is used to calculate the temperature through the intensity ratio of Stokes light and anti-Stokes light, determine the spatial position corresponding to the temperature using the principle of optical time domain reflectometry, and generate a temperature distribution curve.

[0061] The specific analysis method of the temperature corresponding to the spatial position is: from the mean sequence, respectively extracting the Stokes light signal intensity value and the anti-Stokes light signal intensity value corresponding to the same spatial position, calculating the ratio of the Stokes light intensity value to the anti-Stokes light intensity value, and obtaining the Raman scattering intensity ratio.

[0062] A preset temperature calibration curve is called, which is a mapping relationship between Raman scattering intensity ratios and temperature values. The Raman scattering intensity ratios are substituted into the calibration curve to calculate the temperature value of the corresponding spatial position. The corresponding relationship between the optical signal intensity ratio and temperature can be used to accurately calculate the temperature of the corresponding spatial position through the known temperature calibration curve, thereby achieving precise temperature measurement.

[0063] It should be noted that the specific analysis method of the temperature calibration curve is: pre-calibrate the sensing optical fiber at multiple points using a standard blackbody furnace, and use a piecewise polynomial fitting method to establish a mapping relationship between the Raman scattering intensity ratio and the temperature value to form a temperature calibration curve.

[0064] See also Figure 3 As shown, the specific analysis method of the temperature solution module is: record the starting time when the optical pulse emission module injects the laser pulse into the sensing optical fiber, and at the same time detect the receiving time when the scattered signal reaches the photoelectric conversion module, and calculate the time difference between the receiving time and the starting time.

[0065] The material refractive index parameters of the sensing optical fiber are obtained, and based on the principle of optical time domain reflection, the time difference is multiplied by the speed of light and divided by twice the material refractive index to calculate the spatial position distance corresponding to the scattering signal.

[0066] The spatial position distance is mapped to the specific physical position coordinates on the sensing optical fiber, and a one-to-one correspondence between the temperature value and the physical position coordinates is established; the spatial position corresponding to the scattered signal can be accurately determined, and the distribution of temperature on the sensing optical fiber can be intuitively presented, facilitating comprehensive and accurate monitoring and analysis of the temperature.

[0067] The temperature values of all spatial positions calculated within the same measurement cycle are associated with the corresponding physical position coordinates to generate a temperature-position mapping table. Based on the temperature-position mapping table, a continuous temperature distribution curve is generated with the physical position as the horizontal axis and the temperature value as the vertical axis.

[0068] The calibration correction module is used to select constant temperature reference points, fit the temperature deviation curve to generate calibration coefficients, correct the temperature and calibrate the calibration curve, and compensate for light intensity attenuation.

[0069] The specific analysis method of the calibration curve is: setting constant temperature reference points of known temperature at the starting end, middle section and end position of the sensing optical fiber respectively, automatically collecting the standard temperature value of the constant temperature reference point according to the set time, and recording it as the standard temperature value of each constant temperature reference point at each time point.

[0070] The temperature deviation curve is formed by subtracting the standard temperature value of each constant temperature reference point at each time point from the corresponding temperature value on the temperature calibration curve, and the temperature deviation curve is fitted to generate a calibration coefficient matrix. The calibration coefficient matrix is substituted into the temperature correction formula, and the linear correction mode or the nonlinear correction mode is adopted in real time according to the temperature fluctuation range, and the temperature calibration curve is recalibrated using the corrected temperature value; the temperature calibration curve can be calibrated and corrected according to the actually measured temperature value, so that the temperature calibration curve is more in line with the actual situation, thereby improving the accuracy and reliability of temperature measurement.

[0071] It should be noted that when the absolute value of the set temperature fluctuation is less than the set threshold, the linear correction mode is adopted. The formula of the linear correction mode is: When the absolute value of the set temperature fluctuation is greater than or equal to the set threshold, the nonlinear correction mode is adopted. The formula of the nonlinear correction mode is: ,in Indicates the standard temperature value, represents the corrected temperature, is the calibration coefficient matrix.

[0072] The specific analysis method for compensating for light intensity attenuation is as follows: dividing the sensing optical fiber into several small segments of fixed length according to length, obtaining the initial attenuation coefficient of each segment of the sensing optical fiber from a management database, establishing a model for how the attenuation coefficient changes with temperature, using a trapezoidal integration method to approximately calculate the cumulative attenuation from the starting end of the sensing optical fiber to a certain position on the sensing optical fiber, calculating a compensation factor based on the attenuation, compensating for the scattered light intensity at that position, thereby obtaining the final compensated light intensity, and thereby correcting the corresponding relationship between the temperature value and the light intensity; the method can effectively compensate for the influence of light intensity attenuation on the measurement results, ensure the accuracy of the light intensity, thereby improving the accuracy of temperature measurement, and making the corresponding relationship between the temperature value and the light intensity more accurate.

[0073] It should be noted that the model of the attenuation coefficient changing with temperature is: ,in For the The initial attenuation coefficient of the fiber segment, , is the temperature-dependent attenuation coefficient (typical value 0.002dB / km / C), For a certain position on the sensing fiber, the trapezoidal integration method is used to approximate the cumulative attenuation from the beginning of the sensing fiber to that position. ,in for The serial number of the segment, Respectively Paragraph, Section The initial attenuation coefficient of the optical fiber segment, and the compensation factor is calculated based on the attenuation , the scattered light intensity at this position To make compensation: Get the final compensated light intensity .

[0074] The real-time monitoring and early warning module is used to set multi-level temperature warning thresholds, monitor temperature anomalies, record abnormal information and trigger corresponding level early warning responses.

[0075] The specific analysis method of the real-time monitoring and early warning module is: set multiple levels of temperature early warning thresholds respectively. When the temperature at a certain position of the sensing optical fiber is detected to exceed a certain level of early warning threshold, the position is judged as a temperature abnormality point, and the temperature value of the abnormal point and the time when the abnormality is detected are recorded.

[0076] Based on the calibrated and corrected temperature data, multi-level temperature warning thresholds are preset. The multi-level temperature warning thresholds include an absolute temperature threshold, a relative temperature threshold calculated based on historical temperature data, and a temperature change rate threshold. The absolute temperature threshold is used to set specific temperature values for different levels of warnings, the relative temperature threshold is calculated based on statistics such as the mean and standard deviation of historical temperature data, and the temperature change rate threshold is used to measure the amplitude of temperature change per unit time.

[0077] The temperature of each position of the sensing optical fiber is monitored in real time. When the temperature at a certain position meets any of the following conditions, the position is determined to be a temperature anomaly point: the temperature exceeds the absolute temperature threshold, the temperature exceeds the relative temperature threshold calculated based on historical temperature data, or the temperature change rate exceeds the set temperature change rate threshold.

[0078] After determining that a certain location is a temperature anomaly point, the temperature value of the anomaly point and the time when the anomaly was detected are recorded, and the specific physical position coordinates of the anomaly point on the sensing optical fiber are obtained according to the temperature distribution curve. Different levels of early warning responses are triggered according to the degree of deviation between the temperature value of the anomaly point and the preset multi-level temperature early warning threshold. The system can promptly detect temperature anomalies on the sensing optical fiber, and by setting multi-level thresholds and different levels of early warning responses, it can monitor and warn temperature changes in more detail, provide protection for the safe operation of the system, and facilitate timely adoption of corresponding measures to deal with temperature anomalies.

[0079] It should be noted that the specific content of the different levels of warning responses is: when the temperature exceeds the absolute temperature threshold ratio or the degree of exceeding the relative temperature threshold reaches the set first-level warning standard, the first-level warning is triggered, a local sound and light alarm is issued, and a text message notification is sent to the relevant operation and maintenance personnel.

[0080] When the temperature exceeds the absolute temperature threshold by a certain percentage or exceeds the relative temperature threshold by a certain degree, reaching the set secondary warning standard, a secondary warning is triggered, emergency lighting is activated, the system monitoring frequency is increased to 1 second per time, and a pop-up reminder is pushed to relevant personnel through the application.

[0081] When the temperature exceeds the absolute temperature threshold by a certain percentage or exceeds the relative temperature threshold by a certain degree, reaching the set third-level warning standard, or the temperature reaches the material's tolerance limit, a third-level warning is triggered, the power supply of the equipment related to the abnormal point is shut down, the fire sprinkler system is activated, and an emergency notice is sent to all relevant persons in charge.

[0082] Management database, used to store optical fiber attenuation coefficient, constant temperature reference point temperature, temperature calibration curve, warning threshold, temperature-position mapping table and historical temperature data.

[0083] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention, which are still covered by the scope of protection of the present invention.

Claims

1. A distributed optical fiber temperature measurement system based on Raman scattering, characterized in that: include: Optical signal excitation and separation module, used to separate Stokes light and anti-Stokes light through a beam splitter and dual-wavelength optical filter, monitor optical power in real time, and automatically adjust laser output power; The signal acquisition and preprocessing module is used to divide the spatial position based on the principle of optical time domain reflectometry, calculate the minimum accumulation number algorithm, and perform digital accumulation and noise reduction on the scattered signal; The temperature calculation module is used to calculate the temperature through the intensity ratio of Stokes light and anti-Stokes light, determine the spatial position corresponding to the temperature using the principle of optical time domain reflectometry, and generate a temperature distribution curve; The calibration correction module is used to select a constant temperature reference point, fit the temperature deviation curve to generate a calibration coefficient, correct the temperature and calibrate the calibration curve, and compensate for light intensity attenuation; Real-time monitoring and early warning module, used to set multi-level temperature warning thresholds, monitor temperature anomalies, record abnormal information and trigger corresponding level warning responses; Management database, used to store optical fiber attenuation coefficient, constant temperature reference point temperature, temperature calibration curve, warning threshold, temperature-position mapping table and historical temperature data.

2. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 1, characterized in that: The specific analysis method of the optical signal excitation and separation module is: The laser pulse is injected into the sensing fiber, and the backscattered light generated when the laser pulse propagates in the sensing fiber is initially separated by a beam splitter, and the Stokes light and anti-Stokes light are further separated using a dual-wavelength optical filter. The power of the separated Stokes light and anti-Stokes light is monitored. When the monitored optical power deviates from the set reasonable range of optical power, an alarm mechanism is triggered and the laser output power is automatically adjusted to compensate.

3. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 1, characterized in that: The specific analysis method for dividing the spatial position is: Presetting a segmentation parameter for a single measurement of a scattered signal, wherein the segmentation parameter includes a spatial position range corresponding to each data segment, and the spatial position range is determined based on the principle of optical time domain reflectometry and in combination with the length of the sensing optical fiber; Based on the system noise characteristics and the target signal-to-noise ratio, the minimum number of accumulations required to meet the signal quality requirements is calculated, and the optical pulse emission module is controlled to inject laser pulses into the sensing fiber to stimulate the generation of a scattered signal containing temperature information. The scattered signal is then transmitted to the digital accumulation unit for photoelectric conversion and digital processing. The digitized scattered signal is segmented in the time domain, and each time window corresponds to a data segment. Each time window is converted into a specific spatial position area on the sensing optical fiber, and the segmented data segments are stored in the cache area of the corresponding spatial position according to the corresponding relationship.

4. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 3, characterized in that: The specific analysis method of the minimum cumulative number of times is: The system's white noise power spectrum density is obtained by measuring the system output in the absence of signal input. At the same time, the system's operating bandwidth and the absolute temperature of the system's operating environment are determined. According to the temperature measurement accuracy requirements, the target signal-to-noise ratio is set and converted from decibels to a linear value. This is then substituted into the calculation formula for the minimum number of accumulations to obtain the minimum number of accumulations that meets the signal quality requirements.

5. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 4, characterized in that: The specific analysis method for performing digital accumulation noise reduction on the scattered signal is: Perform multiple measurements according to the minimum accumulation times, each measurement generating a scattered signal data segment corresponding to each spatial position and storing the segment in a corresponding buffer area, thereby forming multiple sets of scattered signal data segmented by spatial position; For the same spatial location buffer, extract the data segments corresponding to multiple measurements in sequence, superimpose and sum the values of the corresponding data points in the multiple measurement signals of the same spatial location, and divide the sum of the superimposed signals by the number of measurements to obtain the mean data point of the spatial location; Traverse the data segments of all spatial positions and generate a mean sequence containing the mean data points of each spatial position.

6. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 1, characterized in that: The specific analysis method of the temperature corresponding to the spatial position is: extracting the Stokes light signal intensity value and the anti-Stokes light signal intensity value corresponding to the same spatial position from the mean value sequence, calculating the ratio of the Stokes light intensity value to the anti-Stokes light intensity value, and obtaining the Raman scattering intensity ratio; A preset temperature calibration curve is called, wherein the calibration curve is a mapping relationship between Raman scattering intensity ratio and temperature value, and the Raman scattering intensity ratio is substituted into the calibration curve to calculate the temperature value of the corresponding spatial position.

7. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 6, characterized in that: The specific analysis method of the temperature solution module is: Recording the start time of the laser pulse injection from the optical pulse emission module into the sensing optical fiber, detecting the reception time of the scattered signal arriving at the photoelectric conversion module, and calculating the time difference between the reception time and the start time; Obtain the material refractive index parameters of the sensing optical fiber, and based on the principle of optical time domain reflectometry, multiply the time difference by the speed of light and divide it by twice the material refractive index to calculate the spatial position distance corresponding to the scattered signal; Mapping the spatial position distance to specific physical position coordinates on the sensing optical fiber, and establishing a one-to-one correspondence between the temperature value and the physical position coordinates; The temperature values of all spatial positions calculated within the same measurement cycle are associated with the corresponding physical position coordinates to generate a temperature-position mapping table. Based on the temperature-position mapping table, a continuous temperature distribution curve is generated with the physical position as the horizontal axis and the temperature value as the vertical axis.

8. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 1, characterized in that: The specific analysis method of the calibration curve is: Setting constant temperature reference points of known temperature at the beginning, middle and end of the sensing optical fiber, respectively, and automatically collecting the standard temperature values of the constant temperature reference points according to the set time interval, and recording them as the standard temperature values of each constant temperature reference point at each time point; The temperature deviation curve is formed by subtracting the standard temperature value of each constant temperature reference point at each time point from the corresponding temperature value on the temperature calibration curve. The temperature deviation curve is fitted to generate a calibration coefficient matrix. The calibration coefficient matrix is substituted into the temperature correction formula. The linear correction mode or the nonlinear correction mode is determined in real time according to the temperature fluctuation range, and the temperature calibration curve is recalibrated using the corrected temperature value.

9. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 8, characterized in that: The specific analysis method for compensating for light intensity attenuation is: The sensing fiber is divided into several small segments of fixed length according to its length. The initial attenuation coefficient of each segment of the sensing fiber is obtained from the management database. A model of the attenuation coefficient changing with temperature is established. For a certain position on the sensing fiber, the trapezoidal integration method is used to approximately calculate the cumulative attenuation from the starting end of the sensing fiber to that position. The compensation factor is calculated based on the attenuation, and the scattered light intensity at that position is compensated to obtain the final compensated light intensity, thereby correcting the correspondence between temperature value and light intensity.

10. The distributed optical fiber temperature measurement system based on Raman scattering according to claim 1, characterized in that: The specific analysis method of the real-time monitoring and early warning module is: Set multiple levels of temperature warning thresholds. When the temperature at a certain position of the sensing optical fiber exceeds a certain warning threshold, the position is judged as a temperature abnormality point, and the temperature value of the abnormal point and the time when the abnormality was detected are recorded. Based on the calibrated and corrected temperature data, a multi-level temperature warning threshold is preset. The multi-level temperature warning threshold includes an absolute temperature threshold, a relative temperature threshold calculated based on historical temperature data, and a temperature change rate threshold. The absolute temperature threshold is used to set specific temperature values for different levels of warnings. The relative temperature threshold is calculated based on statistics such as the mean and standard deviation of historical temperature data. The temperature change rate threshold is used to measure the magnitude of temperature change per unit time. Real-time monitoring of the temperature at each location of the sensing optical fiber. When the temperature at a location meets any of the following conditions, the location is determined to be a temperature anomaly: the temperature exceeds the absolute temperature threshold, the temperature exceeds the relative temperature threshold calculated based on historical temperature data, or the temperature change rate exceeds the set temperature change rate threshold; After determining that a certain location is a temperature anomaly point, the temperature value of the anomaly point and the time when the anomaly is detected are recorded, and its specific physical position coordinates on the sensing optical fiber are obtained based on the temperature distribution curve. Different levels of warning responses are triggered based on the degree of deviation between the temperature value of the anomaly point and the preset multi-level temperature warning threshold.

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