Multi-point distributed temperature detection method and system based on multi-core optical fiber structure

Abstract

The invention provides a multi-point distributed temperature detection method and system based on a multi-core optical fiber structure. Wherein grating array etching processing is carried out on at least three fiber cores to form a specific reflection wavelength interval; when an external light source is incident, the fiber core grating structures reflect optical signals with corresponding wavelengths to generate reflected optical signals with different wavebands; the method comprises the following steps: dividing a reflected light signal channel through a wavelength branching device, generating independent channel signals of each fiber core, and simultaneously carrying out time sequence separation on multi-grating signals in the same fiber core to obtain reflected signals in discrete time sequence distribution; combining the independent channel signal with the discrete reflection signal, performing interference comparison with the fixed wavelength reference optical signal, generating a phase difference interference signal reflecting wavelength shift, and analyzing the wavelength shift to obtain temperature-related wavelength shift data; and through analysis and stress error elimination under deformation constraint, outputting a temperature detection result. According to the technical scheme provided by the invention, the accuracy of distributed temperature detection is improved.

Description

Technical Field

[0001] The present application relates to the field of optical fiber sensing technology, and in particular to a multi-point distributed temperature detection method and system based on a multi-core optical fiber structure. Background Art

[0002] In industrial scenarios like petrochemicals and power transmission, real-time, high-precision monitoring of the temperature distribution of long-distance pipelines or equipment is required. Traditional point-based temperature measurement technologies struggle to meet these distributed measurement requirements. Multi-core optical fiber, with its spatial resolution and resistance to electromagnetic interference, is an ideal temperature sensing medium.

[0003] Currently, the more advanced solution uses single-core optical fiber combined with Raman scattering and optical frequency domain reflection technology to achieve temperature measurement by analyzing the frequency shift of backscattered light.

[0004] This solution has three main limitations: first, the Raman scattering signal intensity is weak, and the low signal-to-noise ratio limits the temperature measurement accuracy; second, the single-core structure cannot distinguish between temperature and strain cross-sensitivity and is easily affected by mechanical vibration; third, optical frequency domain reflection technology has extremely high requirements on the coherence of the light source, and the system is complex and expensive. Summary of the Invention

[0005] The present application provides a multi-point distributed temperature detection method and system based on a multi-core optical fiber structure to solve the problem of low accuracy in the prior art.

[0006] In a first aspect, the present application provides a multi-point distributed temperature detection method based on a multi-core optical fiber structure, comprising: Based on the core structure of a multi-core optical fiber, at least three cores are etched with a grating array to obtain a reflection wavelength range; When an external light source is incident on the multi-core optical fiber, the grating structure of each core reflects the light signal of the corresponding wavelength according to the reflection wavelength range, thereby generating reflected light signals of different wavelength bands; The reflected light signals of the different wavelength bands are divided into channels by using a wavelength splitting device to generate independent channel signals corresponding to each fiber core, and the reflected light signals corresponding to multiple grating structures in the same fiber core are separated in time sequence by using a time sequence separation technology to generate discrete reflected signals with discrete time sequence distribution; After combining the independent channel signal and the discrete reflection signal, interference contrast processing is performed with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset. The wavelength offset is analyzed based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength offset data for each grating structure. A multi-core joint analysis is performed on the difference in the temperature-related wavelength offset data, and a bending stress error elimination process is performed in combination with the constraint relationship of the core position being fixed during the torsional deformation of the multi-core optical fiber to generate a temperature detection result with independent axial distribution of each core.

[0007] Optionally, after combining the independent channel signal and the discrete reflection signal, interference contrast processing is performed with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset, including: The independent channel signals from different fiber cores and the discrete reflection signals after time separation in the same fiber core are optically superimposed by an optical signal combining device to form a composite optical signal; The composite optical signal and a reference optical signal of a preset fixed wavelength generate an interference reaction in an interference device, wherein the optical path difference of the interference device is set to generate interference fringes between each wavelength component in the composite optical signal and the reference optical signal; spatially sampling the interference fringes to obtain a light intensity signal including a phase distribution; Calculating the phase difference variation corresponding to each wavelength component according to the intensity variation of adjacent sampling points in the light intensity signal; The phase difference variation is mapped and associated with the reflection wavelength range to determine a phase difference interference signal reflecting the wavelength shift.

[0008] Optionally, wavelength shift analysis is performed based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength shift data of each grating structure, including: Establishing a corresponding relationship data set between the phase difference variation and the wavelength offset according to a preset reflection wavelength range of the grating structure during etching; Matching the phase difference variation of different wavelength components in the phase difference interference signal with the corresponding relationship data set to determine the initial wavelength offset of each wavelength component; Performing a temperature-dependent correction on the initial wavelength offset based on parameters of the physical characteristics of the grating structure, wherein the parameters of the physical characteristics include a synthetic proportional coefficient of a thermo-optical effect coefficient of a grating structure material; The temperature-dependent wavelength offset of the grating structure is calculated by multiplying the synthesis proportional coefficient by the phase difference variation. The temperature-dependent wavelength shifts of multiple grating structures in the same fiber core are subjected to axial distribution integration processing to generate temperature-dependent wavelength shift data.

[0009] Optionally, a multi-core joint analysis is performed on the difference in the temperature-related wavelength shift data, and bending stress error elimination processing is performed in combination with the constraint relationship of the core position being fixed during torsional deformation of the multi-core optical fiber to generate temperature detection results independently distributed in the axial direction of each core, including: Comparing the temperature-related wavelength shift data of different fiber cores at the same axial position to construct a wavelength shift difference data set between fiber cores; Based on the geometric constraint relationship that the relative positions of the cores of the multi-core optical fiber are fixed during torsional deformation, a mapping rule is established between the wavelength offset difference dataset between the cores and the deformation stress distribution; According to the correspondence between the geometric position relationship between the fiber cores and the stress distribution gradient in the mapping rule, a proportional analysis is performed on the wavelength offset difference of each fiber core to calculate the stress influence correction coefficient of each fiber core; Performing a superposition operation on the stress influence correction coefficient and the temperature-related wavelength offset data of the corresponding fiber core to eliminate the coupling interference of deformation stress on the wavelength offset and generate corrected wavelength data; The corrected wavelength data are independently arranged and combined according to the axial position to generate temperature detection results independently distributed in the axial direction of each fiber core.

[0010] Optionally, performing a superposition operation on the stress influence correction coefficient and the temperature-related wavelength offset data of the corresponding fiber core to eliminate the coupling interference of deformation stress on the wavelength offset and generate the corrected wavelength data includes: Converting the stress influence correction coefficient into a wavelength compensation amount through a preset proportional conversion relationship, wherein the value of the wavelength compensation amount is proportional to the absolute value of the correction coefficient and has an opposite sign to the sign of the stress influence correction coefficient; Adding the temperature-related wavelength offset data at the same axial position and the wavelength compensation amount of the corresponding fiber core point by point in the order of the fiber core numbers to obtain added data; Performing validity verification on the added data to obtain a verification result, and when the verification result exceeds a preset reflection wavelength range, truncating the verification result to the nearest boundary value of the range; The nearest boundary value is stored as the corrected wavelength data.

[0011] Optionally, the composite optical signal and a reference optical signal of a preset fixed wavelength generate an interference reaction in an interference device, wherein the optical path difference of the interference device is set to generate interference fringes between each wavelength component in the composite optical signal and the reference optical signal, including: The composite optical signal and the reference optical signal are respectively fed into a beam splitter of an interference device, and the beam splitter guides the two optical signals into a first optical path and a second optical path respectively; adjusting the optical path length of the first optical path so that a difference between the optical path lengths of each wavelength component in the composite optical signal and the reference optical signal in the second optical path is greater than a maximum allowable difference corresponding to the temporal stability of the composite optical signal, and generating output optical signals of the first optical path and the second optical path; The output optical signals are superimposed by an optical signal synthesis element to form spatially distributed interference fringes.

[0012] Optionally, performing temperature-dependent correction on the initial wavelength offset based on parameters of physical characteristics of the grating structure includes: Multiplying the initial wavelength offset by a temperature sensitivity coefficient of the grating structure material to obtain a multiplication result, wherein the temperature sensitivity coefficient is obtained through experimental calibration and represents the wavelength offset caused by a unit temperature change; performing range verification on the multiplication result according to a preset reflection wavelength range of the grating structure in the etching process to obtain a range verification result; When the multiplication result exceeds the range verification result, replacing the multiplication result with a boundary value of the range to generate replacement processed data; The data obtained by the replacement process is recorded as the wavelength shift after temperature correction.

[0013] In a second aspect, the present application provides a multi-point distributed temperature detection system based on a multi-core optical fiber structure, comprising: A grating etching module is used to perform grating array etching on at least three cores based on the core structure of a multi-core optical fiber to obtain a reflection wavelength range; A signal reflection module, configured to, when an external light source is incident on the multi-core optical fiber, cause the grating structure of each fiber core to reflect the light signal of the corresponding wavelength according to the reflection wavelength range, thereby generating reflected light signals of different wavelength bands; a signal separation module, configured to divide the reflected light signals of different wavelength bands into channels by using a wavelength splitting device to generate independent channel signals corresponding to each fiber core, and to perform time-series separation on the reflected light signals corresponding to multiple grating structures in the same fiber core by using a time-series separation technology to generate discrete reflected signals with discrete time-series distribution; an interference processing module, configured to combine the independent channel signal and the discrete reflection signal, and then perform interference contrast processing with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset; and perform wavelength offset analysis based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength offset data for each grating structure; The error correction module is used to perform multi-core joint analysis on the difference in the temperature-related wavelength offset data, and to eliminate the bending stress error in combination with the constraint relationship of the fixed core position when the multi-core optical fiber is torsional deformed, so as to generate temperature detection results with independent axial distribution of each core.

[0014] In a third aspect, the present application provides a computing device comprising a processing component and a storage component; the storage component stores one or more computer instructions; the one or more computer instructions are used to be called and executed by the processing component to implement a multi-point distributed temperature detection method based on a multi-core optical fiber structure as described in the first aspect above.

[0015] In a fourth aspect, the present application provides a computer storage medium storing a computer program. When the computer program is executed by a computer, it implements a multi-point distributed temperature detection method based on a multi-core optical fiber structure as described in the first aspect.

[0016] In the embodiment of the present application, based on the core structure of a multi-core optical fiber, at least three optical cores are etched with a grating array to obtain a reflection wavelength range; when an external light source is incident on the multi-core optical fiber, the grating structure of each optical core reflects the light signal of the corresponding wavelength according to the reflection wavelength range, generating reflected light signals of different bands; a wavelength splitting device is used to divide the reflected light signals of the different bands into channels to generate independent channel signals corresponding to each optical core, and at the same time, a timing separation technology is used to perform timing separation on the reflected light signals corresponding to multiple grating structures in the same optical core to generate discrete reflected signals with discrete time series distribution; the After the independent channel signal is merged with the discrete reflection signal, interference contrast processing is performed with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset. The wavelength offset is analyzed based on the linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-related wavelength offset data of each grating structure. A multi-core joint analysis is performed on the difference in the temperature-related wavelength offset data, and a bending stress error elimination process is performed in combination with the constraint relationship of the fixed core position when the multi-core optical fiber is torsional deformed to generate a temperature detection result with independent axial distribution of each core.

[0017] The technical solution of the present application has the following beneficial effects: achieving wavelength-selective reflection of multiple fiber cores, providing a physical basis for wavelength division multiplexing, and ensuring the distinguishability of signals from each fiber core; generating characteristic optical signals related to temperature through precise control of wavelength intervals, and establishing a temperature-wavelength mapping relationship; using wavelength division multiplexing to achieve spatial dimension (between fiber cores) separation, and using timing separation to achieve time dimension (within the fiber core) separation, significantly improving signal capacity; converting tiny wavelength offsets into measurable phase differences through interference contrast, greatly improving temperature detection sensitivity; and utilizing the spatial constraint relationship of multiple fiber cores to decouple temperature and stress cross-sensitivity, thereby improving measurement accuracy by more than 3 times.

[0018] Furthermore, a mixed signal containing multiple wavelength components is formed by superimposing optical powers. After generating resolvable interference fringes through an interferometer, the light intensity signal obtained by spatial sampling is converted into a phase difference variation and mapped to a wavelength offset. Then, based on the reflection wavelength range preset by the etching process and the material's thermo-optical properties, temperature correlation correction and axial integration are performed to ultimately generate temperature data that eliminates stress interference. This solution, through the coordinated processing of wavelength / time division multiplexing and interferometric demodulation, improves the temperature measurement accuracy of multi-core optical fibers while maintaining spatial resolution and enhances their resistance to bending interference.

[0019] These and other aspects of the present application will become more readily apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 A flow chart of a multi-point distributed temperature detection method based on a multi-core optical fiber structure provided by the present application is shown; Figure 2 The present invention provides a schematic diagram of a multi-core optical fiber structure based on a multi-point distributed temperature detection system; Figure 3 A schematic structural diagram of a computing device provided by the present application is shown. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0023] In some of the processes described in the specification and claims of this application and the above-mentioned figures, multiple operations that appear in a specific order are included, but it should be clearly understood that these operations may not be executed in the order in which they appear in this document or may be executed in parallel. The serial numbers of the operations, such as 101, 102, etc., are only used to distinguish between different operations, and the serial numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations may be executed in sequence or in parallel. It should be noted that the descriptions of "first", "second", etc. in this document are used to distinguish different messages, devices, modules, etc., and do not represent a sequential order, nor do they limit "first" and "second" to being different types.

[0024] Existing distributed fiber-optic temperature sensing technologies primarily utilize single-core optical fibers combined with Raman or Brillouin scattering principles. While capable of long-distance measurement, these technologies suffer from three key drawbacks: First, scattering-based temperature measurement solutions suffer from a low signal-to-noise ratio, resulting in limited temperature resolution. Second, single-core structures are unable to distinguish between temperature and strain, leading to significant errors in mechanical vibration environments such as pipeline monitoring. Finally, existing solutions rely on highly coherent light sources and complex demodulation equipment, making it difficult to meet the low-cost, high-robustness requirements of industrial scenarios. These drawbacks stem from the insufficient signal capacity and single physical dimension of the single-core sensing structure, which makes it impossible to simultaneously achieve high-precision measurement and multi-parameter decoupling.

[0025] In response to the above problems, this application proposes a multi-point distributed temperature detection method based on a multi-core optical fiber structure. Its innovation lies in: by etching FBG arrays with different wavelength ranges in each core of the multi-core optical fiber, a sensing network with three-dimensional encoding of space, wavelength and time is constructed; wavelength division multiplexing is used to realize parallel acquisition of multi-core signals, and time division multiplexing is combined to improve the spatial resolution of multiple measurement points in a single core; finally, multi-core interference demodulation and collaborative error correction are used to achieve precise separation of temperature and stress. This method has a breakthrough in improving the signal-to-noise ratio and reduces cross-sensitivity errors by utilizing the geometric constraint characteristics of multi-core optical fibers. Compared with traditional solutions, while maintaining spatial resolution, the system cost is reduced, fundamentally solving the three core problems of insufficient measurement accuracy, poor anti-interference ability and high cost in the existing technology. It is particularly suitable for high-reliability temperature monitoring in complex industrial environments such as oil pipelines and high-voltage cables.

[0026] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0027] Figure 1The present invention provides a flow chart of a multi-point distributed temperature detection method based on a multi-core optical fiber structure, as shown in FIG. Figure 1 As shown, the method includes: 101. Based on the core structure of a multi-core optical fiber, grating array etching is performed on at least three cores to obtain a reflection wavelength range; In this step, multi-core fiber is a special fiber structure containing multiple independent cores, each capable of independently transmitting optical signals. The grating array etching process uses processes such as ultraviolet lasers to create a periodic refractive index modulation structure within the fiber core, forming a series of fiber Bragg gratings. The reflection wavelength range refers to the ability of each grating structure to reflect optical signals within a specific wavelength range. Gratings in different fiber cores are designed to reflect signals in different wavelength bands.

[0028] In the embodiments of this application, a suitable multi-core optical fiber is first selected to determine the number of cores to be etched. Grating etching is then performed on the selected cores using an ultraviolet laser phase mask method. During the etching process, the laser parameters and exposure time are precisely controlled to ensure that the grating array of each core has a specific reflection wavelength range, and that the reflection bands of adjacent cores do not overlap. After etching is completed, a spectrum analysis device is used to verify the reflection characteristics of the gratings on each core to ensure that the design requirements are met.

[0029] In an actual case, grating arrays with central wavelengths of 1550nm, 1555nm, and 1560nm were etched on the three cores of a triple-core optical fiber. The reflection bands were separated by 5nm, and the reflection bandwidth was controlled within 0.3nm.

[0030] 102. When an external light source is incident on the multi-core optical fiber, the grating structure of each fiber core reflects the light signal of the corresponding wavelength according to the reflection wavelength range, thereby generating reflected light signals of different wavelength bands; In this step, the external light source refers to a broadband light source that can cover all grating reflection bands. The reflected light signals of different wavelength bands refer to the grating structure of each fiber core selectively reflecting light signals of a specific wavelength range according to its reflection characteristics.

[0031] In this embodiment, a broadband light source is injected into a multi-core optical fiber through a fiber circulator. The spectrum of the light source must completely cover the reflection wavelengths of all the core gratings. As the optical signal propagates through the fiber, the grating structures of each core selectively reflect the corresponding optical signal wavelengths according to their preset reflection wavelength ranges, while the remaining wavelengths continue to be transmitted. The reflected optical signal is output through another port of the circulator and enters the subsequent signal processing unit.

[0032] Continuing with the above example, an ASE light source with a bandwidth of 50nm is injected into the optical fiber. The grating of fiber core A reflects the optical signal in the 1550nm band, fiber core B reflects the 1555nm band, and fiber core C reflects the 1560nm band. These reflected optical signals are output to the wavelength division multiplexing device through the circulator.

[0033] 103. Use a wavelength splitting device to divide the reflected light signals of different wavelength bands into channels to generate independent channel signals corresponding to each fiber core, and use a timing separation technology to perform timing separation on the reflected light signals corresponding to multiple grating structures in the same fiber core to generate discrete reflected signals with discrete timing distribution; In this step, the wavelength splitter is an optical device that separates optical signals of different wavelengths into different channels. Independent channel signals refer to the reflected light signals from each fiber core being separated into different output channels after wavelength division multiplexing. Time-sequential separation technology achieves signal separation by controlling the pulse characteristics of the light source and the detection time window. Discrete reflection signals refer to the chronological sequence of reflected light pulses obtained after time-sequential separation.

[0034] In this embodiment, the reflected light signals from each fiber core are first input into a wavelength splitter, which separates the signals from different fiber cores into independent output channels based on wavelength. The optical signal in each channel is then pulse-modulated, and a high-speed detector is used to detect the temporal characteristics of the reflected light pulses. By precisely controlling the detection time window, the grating reflection signals at different locations within the same fiber core can be separated, forming a discrete sequence of reflected signals.

[0035] Continuing with the above example, an arrayed waveguide grating (AWG) was used to introduce optical signals of 1550 nm, 1555 nm, and 1560 nm into three independent channels. A 100 ns optical pulse was then applied to each channel. Time-domain reflectometry was used to detect the reflected pulses from the gratings at different positions, and the signals from each grating were distinguished based on the pulse arrival time.

[0036] 104. After combining the independent channel signal and the discrete reflection signal, perform interference contrast processing with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset. Perform wavelength offset analysis based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength offset data for each grating structure. In this step, the reference optical signal refers to a reference optical signal with a fixed wavelength and stable characteristics. The phase difference interference signal is the information obtained by interferometer measurement that reflects the phase change of the optical signal. The temperature linear relationship describes how the grating reflection wavelength changes with temperature.

[0037] In this embodiment, the separated optical signals from each fiber core are first fed into an interferometer along with a reference optical signal. By adjusting the optical path length difference in the interferometer, clear interference fringes are generated between the composite optical signal and the reference optical signal. A photodetector array is then used to collect the intensity distribution of the interference fringes. By analyzing the phase variation characteristics of the fringes, the wavelength offset of each grating reflection signal is calculated. This wavelength offset is then converted to a corresponding temperature change value based on a pre-calibrated temperature sensitivity coefficient.

[0038] Continuing with the above example, the 1550nm fiber core A signal interferes with the 1549nm reference light in the interferometer. By measuring the movement of the interference fringes, the 0.1nm wavelength shift is calculated. Based on the sensitivity coefficient of 10pm / °C, the 10°C temperature change is calculated.

[0039] 105. Perform multi-core joint analysis on the difference in the temperature-related wavelength offset data, perform bending stress error elimination processing based on the constraint relationship of the core position being fixed during torsional deformation of the multi-core optical fiber, and generate temperature detection results with independent axial distribution of each core.

[0040] In this step, the core position constraint refers to the property of the multi-core fiber to maintain the relative position relationship between the cores when deforming. Bend stress error elimination refers to the mutual correction of multi-core measurement data to eliminate measurement errors caused by fiber bending.

[0041] In this embodiment, temperature-related wavelength offset data for each fiber core at the same measurement location is first collected, and the differences between the data for each core are analyzed. Based on the structural characteristics of the multi-core optical fiber, a mathematical model of the core position and stress distribution is established. This model is used to calculate the error component caused by bending stress in the measurement data of each core. The original measurement data is then corrected to obtain the true temperature data after the stress effect is eliminated.

[0042] Continuing with the above example, when the temperature data of the three fiber cores at the same position are different, the influence of the bending stress is calculated based on the spatial distribution relationship of the fiber cores, and the data of each fiber core is compensated and corrected to finally obtain a consistent and accurate temperature value.

[0043] In summary, steps 101 to 105 achieve a complete distributed temperature detection solution by fabricating a specially designed grating array on a multi-core optical fiber, utilizing wavelength-division multiplexing and time-division multiplexing to separate signals, employing interferometry to improve detection sensitivity, and finally eliminating measurement errors based on the spatial constraints of the multiple fiber cores. This approach achieves high-spatial-resolution temperature distribution measurement, effectively overcoming the signal crosstalk and stress cross-sensitivity issues inherent in traditional methods, improving measurement accuracy and reliability, and making it suitable for temperature monitoring in a variety of complex environments.

[0044] In order to solve the problems of signal coupling interference and insufficient demodulation accuracy in multi-core optical fiber temperature detection, in some embodiments, after combining the independent channel signal and the discrete reflection signal in step 104, interference contrast processing is performed with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset, including: 210. Superimpose the independent channel signals from different fiber cores and the discrete reflection signals after time separation in the same fiber core through an optical signal combining device to form a composite optical signal; In step 201, the optical signal combining device is an optical device (such as a fiber coupler) that realizes linear superposition of optical power and is used to combine multiple input signals. The composite optical signal is a composite optical signal containing multiple fiber core wavelength components and timing characteristics.

[0045] In this embodiment, the wavelength-division-multiplexed independent channel signals (cores A / B / C correspond to 1550 / 1555 / 1560 nm signals, respectively) and the discrete reflection signals separated by time within the same core (e.g., the pulse signals from the three gratings within core A) are first input into a fiber coupler. The coupler adds the optical power of each signal, preserving the amplitude and phase information of each wavelength component. For example, the 1550 nm continuous wave signal from core A and the pulse reflection signals from its three gratings are combined into a composite optical signal, forming a composite optical field interwoven in the time and space domains.

[0046] 202. The composite optical signal and a reference optical signal of a preset fixed wavelength generate an interference reaction in an interference device, wherein the optical path difference of the interference device is set to generate interference fringes between each wavelength component in the composite optical signal and the reference optical signal; In step 202, the interferometer is an optical structure that generates an optical path difference (such as a Mach-Zehnder interferometer). The optical path difference setting means that the optical path difference between different wavelength components and the reference light exceeds their coherence length to ensure that the interference fringes are distinguishable.

[0047] In this embodiment, a composite optical signal and a reference optical signal (e.g., a 1549nm narrow-linewidth laser) are fed into two separate optical paths of an interferometer. By adjusting the mechanical displacement mechanism of the reference arm, the optical path difference between each wavelength component in the composite optical signal (e.g., 1550nm and 1555nm) and the reference light is set to be greater than its coherence length. For example, if the optical path difference of the 1550nm component is set to 25mm (corresponding to a coherence length of 20mm), this wavelength component interferes with the reference light to form fringes with stable spacing, while the 1555nm component forms fringes with slightly varying spacing due to its different optical path difference.

[0048] 203. Perform spatial sampling on the interference fringes to obtain a light intensity signal including a phase distribution; In step 203, spatial sampling refers to collecting light intensity values ​​at fixed intervals along the extension direction of the interference fringes. The light intensity signal refers to a discrete data sequence containing the interference phase distribution of each wavelength component.

[0049] In this embodiment, a linear CCD detector is used to scan along the direction of the interference fringes, with a sampling interval less than one-quarter of the minimum fringe period (e.g., a 10μm fringe period corresponds to a 2.5μm sampling interval). The detector records the light intensity at each sampling point, forming a light intensity distribution curve containing phase gradient information. For example, the interference fringes of a 1550nm component are sampled as a discrete sequence of [high, low, high, low…], with each data point corresponding to the phase state at a specific spatial location.

[0050] 204. Calculate the phase difference variation corresponding to each wavelength component based on the intensity variation of adjacent sampling points in the light intensity signal; In step 204, the phase difference variation refers to the phase difference value reflected by the change in light intensity at adjacent sampling points, and is linearly related to the wavelength offset.

[0051] In this embodiment, the light intensity signal is differentially calculated. Based on the ratio of the intensity variation (ΔI) at adjacent sampling points to the average intensity (I0), the local phase difference (Δφ) is calculated using the interference equation ΔI / I0 = sin(Δφ). For example, the differential calculation result for a certain light intensity sequence is Δφ = 0.8 rad, indicating a temperature-induced phase shift at that location.

[0052] 205. Map and associate the phase difference variation with the reflection wavelength range to determine a phase difference interference signal reflecting the wavelength offset.

[0053] In step 205, mapping association refers to converting the phase difference into a physical quantity through the phase difference-wavelength shift correspondence established by calibration.

[0054] In the embodiment of the present application, according to the correspondence between the pre-calibrated reflection wavelength range and the phase difference change, the phase difference change of each wavelength component is converted into an actual wavelength offset, and finally a phase difference interference signal containing the wavelength offset information of each fiber core is generated.

[0055] Here's a specific example: In an oil pipeline monitoring scenario, cores A (1550nm), B (1555nm), and C (1560nm) of a three-core optical fiber are combined into a composite optical signal in step 210. This signal, combined with a 1549nm reference beam, forms three sets of fringes with varying spacing in the interferometer (step 202). A linear CCD samples at 2.5μm intervals (step 203). Through differential calculation, the phase differences of cores A, B, and C are calculated to be 0.8, 0.82, and 0.85rad, respectively (step 204). These are ultimately mapped to wavelength offsets of 12, 12.3, and 12.75pm (step 205), outputting a phase difference interferometer signal that reflects the pipeline's axial temperature distribution.

[0056] In summary, steps 201 to 205 achieve parallel demodulation and high-precision phase extraction of multi-fiber core signals through the coordinated design of signal merging and interference processing; the interference fringe separation technology based on optical path difference control effectively avoids multi-wavelength crosstalk; the calibration mapping mechanism accurately converts phase changes into physical quantities, significantly improving the reliability and spatial resolution of temperature detection in complex environments.

[0057] In order to solve the problems of cross-sensitivity error and insufficient data integration in multi-core optical fiber temperature detection, in some embodiments, step 104 further includes performing wavelength shift analysis based on the linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-related wavelength shift data of each grating structure, including: 301. Establish a corresponding relationship data set between a phase difference variation and a wavelength offset according to a preset reflection wavelength range of the grating structure during etching. In step 301, the reflection wavelength range refers to the specific reflection wavelength band (e.g., 1550-1555 nm) preset during etching of the grating array. The corresponding relationship dataset refers to the mapping relationship between the phase difference variation and the wavelength offset established in the measurement experiment.

[0058] In an embodiment of the present application, a temperature calibration experiment is first performed on the etched grating array using a tunable laser, and the phase difference change and the corresponding wavelength offset of each grating are recorded at different temperatures; secondly, the data are classified and stored according to the fiber core number, axial position and reflection wavelength; then a multidimensional lookup table of the reflection wavelength range and the phase difference change is established, for example, a 1550nm grating corresponds to a phase difference of 0.5rad at a temperature rise of 10°C; finally, the calibration data is integrated into the demodulation system database to form a corresponding relationship data set that can be queried in real time.

[0059] 302. Match the phase difference variation of different wavelength components in the phase difference interference signal with the corresponding relationship data set to determine the initial wavelength offset of each wavelength component; In step 302, the initial wavelength shift refers to the original wavelength shift value without temperature correction, and contains stress interference components.

[0060] In the embodiment of the application, first, the phase difference change of each wavelength component is extracted from the phase difference interference signal; second, a matching record under the same reflection wavelength range is searched in the corresponding relationship data set; third, the initial wavelength shift corresponding to the current phase difference (such as 0.8 rad mapped to 12 pm) is determined by the linear interpolation method; and finally, the shift of each wavelength component is classified according to the core number to generate an initial wavelength shift list.

[0061] 303, based on the parameter of the physical characteristics of the grating structure, the temperature correlation correction is performed on the initial wavelength shift, wherein the parameter of the physical characteristics includes a synthetic proportional coefficient of the thermal-optic effect coefficient of the grating structure material; In step 303, the synthetic proportional coefficient refers to the temperature sensitivity coefficient of the thermal expansion coefficient and the thermal-optic effect, which represents the wavelength shift caused by unit temperature change.

[0062] In the embodiment of the application, first, the temperature sensitivity coefficient is determined by constant temperature experiment according to the grating material properties (such as the thermal expansion coefficient of quartz optical fiber 0.55×10 ) and packaging process parameters (such as the elastic modulus of the coating layer); second, the coefficients of each grating are stored in the database according to the axial position; third, the synthetic proportional coefficient (such as 10 pm / ℃) corresponding to the current grating is called from the database; and finally, the coefficient is associated with the initial wavelength shift.

[0063] 304, the temperature effect wavelength shift of the grating structure is calculated by the product relationship of the synthetic proportional coefficient and the phase difference change; In step 304, the temperature effect wavelength shift refers to the wavelength shift value caused by temperature change only after eliminating the stress interference.

[0064] In the embodiment of the application, first, the initial wavelength shift (such as 12 pm) is divided by the synthetic proportional coefficient (10 pm / ℃) to obtain the original temperature change (1.2℃); second, the wavelength shift under the pure temperature effect (1.2℃×10 pm / ℃=12 pm) is calculated in reverse according to the linear relationship of the temperature response of the grating material; and finally, it is verified whether the calculation result is within the allowed range of the grating reflection wavelength (such as 1550±2nm), and if not, it is corrected according to the boundary value.

[0065] 305, the temperature effect wavelength shifts of a plurality of grating structures in the same core are axially distributed and integrated to generate temperature-related wavelength shift data.

[0066] In step 305, the axial distribution integration process refers to sorting and associating the temperature-dependent wavelength offsets of multiple gratings in the same fiber core according to their spatial positions.

[0067] In an embodiment of the present application, the temperature-induced wavelength offsets are first sorted according to the axial position coordinates of the grating (e.g., 10 cm, 20 cm, and 30 cm from the starting end); secondly, the adjacent grating data are smoothed and filtered according to the continuous deformation characteristics of the optical fiber; then, the processed data are packaged into an independent temperature distribution sequence according to the fiber core number; finally, the multi-core data are synchronously output to the visualization terminal.

[0068] Here's a specific example: For high-voltage cable temperature monitoring, three gratings were etched into core A of a three-core optical fiber (positions 10, 20, and 30 meters, reflecting a wavelength of 1550 nm). The calibration data set stores a temperature sensitivity coefficient of 10 pm / °C. During testing, the measured phase difference changes were 0.8, 0.85, and 0.9 rad, respectively, matching the initial wavelength offsets of 12, 12.75, and 13.5 pm. After correction using a synthetic proportionality factor, the calculated temperature-dependent wavelength offsets were 12, 12.75, and 13.5 pm. Axial temperature distribution data for core A, sorted by position, was generated, revealing an abnormal temperature increase of 1.275°C in the mid-section (20 meters) of the cable.

[0069] In summary, steps 301 to 305 achieve precise decoupling of temperature and stress through calibration data mapping and physical property correction; axial distribution integration processing forms an intuitive temperature gradient map; multi-fiber collaborative analysis significantly improves measurement reliability in complex deformation environments, providing high-precision temperature distribution data for industrial equipment safety monitoring.

[0070] In order to solve the problem of measurement distortion caused by bending stress interference in multi-core optical fiber temperature detection, in some embodiments, in step 105, a multi-core joint analysis is performed on the difference in the temperature-related wavelength offset data, and bending stress error elimination is performed in combination with the constraint relationship of the core position being fixed when the multi-core optical fiber is torsional deformed, to generate temperature detection results with independent axial distribution for each core, including: 401. Compare the temperature-related wavelength offset data of different fiber cores at the same axial position to construct a wavelength offset difference data set between fiber cores. In step 401, the inter-core wavelength offset difference data set refers to a set of temperature-related wavelength offset differences between different fiber cores at the same axial position, reflecting measurement deviations caused by bending stress.

[0071] In the embodiment of the present application, the temperature-related wavelength offset of each fiber core at the same axial position is first obtained (for example, fiber core A refers to 12pm, fiber core B refers to 15pm, and fiber core C refers to 18pm); secondly, the offset difference between each fiber core is calculated (for example, the difference between A and B is 3pm, the difference between B and C is 3pm, and the difference between C and A is 6pm); then, the difference data is classified and stored according to the axial position coordinates of the optical fiber; finally, a multidimensional data set containing the position, fiber core number and difference value is formed.

[0072] 402. Establishing a mapping rule between the inter-core wavelength offset difference dataset and the deformation stress distribution based on a geometric constraint relationship in which the cores of the multi-core optical fiber are fixed relative to each other during torsional deformation. In step 402, the mapping rule of the deformation stress distribution refers to a stress-wavelength offset relationship model established based on the geometric structure of the multi-core optical fiber, which reflects the correlation between the core position and the stress gradient.

[0073] In the embodiment of the present application, first, a mathematical model of the core spatial coordinates and stress distribution is established based on the core arrangement of the multi-core optical fiber (such as triangular symmetry); secondly, a calibration experiment is performed to measure the wavelength offset difference of each core under different bending degrees; then, the experimental data is fitted into a linear relationship equation between the stress gradient and the offset difference; finally, the equation parameters are integrated into the demodulation system to form a mapping rule library.

[0074] 403. Based on the correspondence between the geometric position relationship between the fiber cores and the stress distribution gradient in the mapping rule, perform a proportional analysis on the wavelength offset difference of each fiber core, and calculate a stress influence correction coefficient of each fiber core; In step 403, the stress influence correction coefficient refers to the weight that characterizes the influence of bending stress on wavelength offset, and is calculated based on the geometric position relationship.

[0075] In the embodiment of the present application, the stress-offset relationship equation corresponding to the current optical fiber deformation mode is first called from the mapping rule library; secondly, the stress gradient distribution is calculated according to the core spacing (such as the spacing between cores A and B is 125μm); then, the correction coefficient of each core is determined by proportional coefficient conversion (such as unit stress gradient corresponds to 0.1pm wavelength offset); finally, a correspondence table between core numbers and correction coefficients is generated (such as core A coefficient -0.2, core B coefficient +0.1, core C coefficient +0.1).

[0076] 404. Perform a superposition operation on the stress influence correction coefficient and the temperature-related wavelength offset data of the corresponding fiber core to eliminate the coupling interference of deformation stress on the wavelength offset and generate corrected wavelength data. In step 404, the corrected wavelength data refers to the wavelength offset after eliminating stress interference, and only reflects the true value of temperature change.

[0077] In the embodiment of the present application, the temperature-related wavelength offset (e.g., core A refers to 12pm) and its corresponding correction coefficient (-0.2) are first read; secondly, the offset is multiplied by the correction coefficient to obtain the compensation amount (12pm×(-0.2)=-2.4pm); then the compensation amount is superimposed on the original offset (12pm+(-2.4pm)=9.6pm); finally, it is verified whether the corrected data is within the allowable range of the grating reflection wavelength. If it exceeds, it is truncated to the boundary value.

[0078] 405. Independently arrange and combine the corrected wavelength data according to axial positions to generate temperature detection results independently distributed in the axial direction of each fiber core.

[0079] In step 405, the axially independently distributed temperature detection results refer to independent temperature data of each fiber core arranged according to the axial position of the optical fiber, eliminating cross interference between fiber cores.

[0080] In the embodiment of the present application, the corrected wavelength data are first sorted according to the axial position coordinates (such as 0m, 10m, 20m); secondly, the data are grouped according to the fiber core number (such as fiber core group A, group B, group C); then each group of data is converted into a temperature value (such as a wavelength offset of 9.6pm corresponds to a temperature rise of 0.96°C); finally, an independent temperature distribution curve graph for each fiber core is output.

[0081] Here's a specific example: During submarine cable monitoring, temperature-related wavelength offsets of 15, 18, and 21 pm were measured at specific axial locations for cores A, B, and C of a seven-core optical fiber (200 μm spacing). After constructing a differential data set (a 3 pm difference between A and B, and a 3 pm difference between B and C), stress gradients were calculated based on a triangular core arrangement model, and correction factors of -0.3, +0.15, and +0.15 were determined. The corrected data yielded 15-4.5 = 10.5 pm, 18+2.7 = 20.7 pm, and 21+3.15 = 24.15 pm. Three independent temperature curves were generated based on axial position, indicating localized overheating in the center of the cable (core B).

[0082] In summary, steps 401 to 405 accurately separate the temperature and stress coupling effects through multi-fiber core difference analysis and geometric constraint modeling; the dynamic correction mechanism effectively eliminates bending deformation interference; and the axially independent data output provides a highly reliable temperature distribution map, significantly improving the accuracy and practicality of optical fiber temperature measurement under complex working conditions.

[0083] In order to solve the problem of data distortion caused by stress interference in multi-core optical fiber temperature detection, in some embodiments, in step 404, the stress influence correction coefficient is superimposed on the temperature-related wavelength offset data of the corresponding optical fiber core to eliminate the coupling interference of deformation stress on the wavelength offset and generate the corrected wavelength data, including: 501. Convert the stress influence correction coefficient into a wavelength compensation value through a preset proportional conversion relationship, wherein the value of the wavelength compensation value is proportional to the absolute value of the correction coefficient and has an opposite sign to the sign of the stress influence correction coefficient; In step 501, the wavelength compensation amount refers to a wavelength adjustment value converted according to the stress influence correction coefficient, which is used to offset the measurement deviation caused by stress.

[0084] The preset proportional conversion relationship refers to a linear correspondence rule between the stress correction coefficient and the wavelength compensation amount established through a calibration experiment.

[0085] In this embodiment, the stress correction coefficient stored in the database is first called (for example, the correction coefficient for core A is -0.2). The wavelength compensation is calculated based on a preset proportional conversion relationship (for example, a unit correction coefficient corresponds to a 5pm compensation). The value is the absolute value of the correction coefficient multiplied by the proportional factor (0.2 × 5pm = 1pm), with the sign opposite to that of the correction coefficient (-0.2 corresponds to +1pm). For example, a correction coefficient of -0.2 for core A is converted to a compensation of +1pm, and a correction coefficient of +0.1 for core B is converted to a compensation of -0.5pm.

[0086] 502. Add the temperature-related wavelength offset data at the same axial position and the wavelength compensation amount of the corresponding fiber core point by point in the order of the fiber core numbers to obtain added data; In step 502, point-by-point addition refers to performing algebraic operations on each data point according to the axial position of the optical fiber, so as to ensure independent correction of each measurement position.

[0087] In this embodiment, the temperature-dependent wavelength offset data for the same axial position is first read sequentially by core number (e.g., the offset for core A at position 10m is 12pm). The wavelength compensation for the corresponding core is then retrieved (+1pm for core A), and the two are algebraically added (12pm + 1pm = 13pm). The correction calculation is then performed across all cores and axial positions to complete the correction calculation for the entire data set. For example, the offset of core B at position 10m, 15pm, is added to the compensation of -0.5pm to obtain 14.5pm.

[0088] 503. Perform validity verification on the added data to obtain a verification result. When the verification result exceeds a preset reflection wavelength range, truncate the verification result to the nearest boundary value of the range. In step 503, validity verification refers to checking whether the corrected data complies with the physical limitation of the grating reflection wavelength.

[0089] The preset reflection wavelength range refers to the effective working wavelength band of the grating defined in the etching process (such as 1550nm±2nm).

[0090] In this embodiment, the summed data is first compared to a preset reflection wavelength range. If the data exceeds the upper limit (e.g., 1552 nm) or lower limit (e.g., 1548 nm), the data is forcibly set to the nearest boundary value. For example, if the corrected result of 1552.3 pm for fiber core C at position 20 m exceeds the upper limit of 1552 pm, it is truncated to 1552 pm. Finally, all verification results are recorded and abnormal data points are marked.

[0091] 504 stores the nearest boundary value as the corrected wavelength data.

[0092] In step 504, the corrected wavelength data refers to the final effective wavelength offset after stress compensation and range constraint processing, which only reflects temperature changes.

[0093] In this embodiment, the verified data is first stored by core number and axial position. A timestamp and location tag are then added to each data point. Finally, the data set is packaged and output in a standardized format. For example, the corrected wavelength data of 13 pm for core A at position 10 m is stored as {core: A; position: 10 m; wavelength offset: 13 pm}.

[0094] Here's a specific example: In natural gas pipeline monitoring, the temperature-related wavelength offsets of cores A, B, and C of a three-core optical fiber measured at a location of 50 m were 18 pm, 22 pm, and 25 pm, respectively. These correspond to stress correction factors of -0.3, +0.15, and +0.15. Using scaling (a scaling factor of 10 pm / unit coefficient), the compensations were +3 pm, -1.5 pm, and -1.5 pm, respectively. Point-by-point summation yielded 21 pm, 20.5 pm, and 23.5 pm. Verification revealed that the 21 pm wavelength of core A exceeded the preset range of 1550 ± 2 nm (i.e., 1548-1552 pm), so it was truncated to 1552 pm. The final stored data showed core A at 1552 pm, core B at 20.5 pm, and core C at 23.5 pm, generating a temperature distribution map at 50 m in the pipeline.

[0095] In summary, steps 501 to 504 effectively eliminate the coupling interference of bending stress on temperature measurement through dynamic compensation and range constraint mechanisms; point-by-point correction ensures the independence and accuracy of each data point; and the standardized data storage format provides reliable input for subsequent analysis, significantly improving the credibility and practicality of temperature detection results under complex working conditions.

[0096] In order to solve the problems of cross-sensitivity error and insufficient data integration in multi-core optical fiber temperature detection, in some embodiments, the composite optical signal in step 202 and a reference optical signal of a preset fixed wavelength generate an interference reaction in an interferometer, wherein the optical path difference of the interferometer is set to generate interference fringes between each wavelength component in the composite optical signal and the reference optical signal, including: 601. The composite optical signal and the reference optical signal are respectively input into a spectrometer of an interference device, and the spectrometer respectively directs the two optical signals into a first optical path and a second optical path; In step 601 , the optical splitter element refers to an optical device (such as a fiber beam splitter or a prism) that distributes an input optical signal to different optical paths in proportion.

[0097] The first optical path and the second optical path refer to two independent transmission paths in the interference device, which are used to generate an optical path difference.

[0098] In this embodiment, a composite optical signal (containing the 1550 / 1555 / 1560nm components of fiber cores A / B / C) and a reference optical signal (1549nm) are first input into a beam splitter, which directs the two signals into the first optical path (measurement arm) and the second optical path (reference arm), respectively. For example, a 50:50 fiber beam splitter is used to distribute the composite optical signal to the first optical path and the reference optical signal to the second optical path, ensuring balanced light intensity between the two paths.

[0099] 602. Adjust the optical path length of the first optical path so that the difference between the optical path lengths of each wavelength component in the composite optical signal and the reference optical signal in the second optical path is greater than the maximum allowable difference corresponding to the time stability of the composite optical signal, thereby generating output optical signals of the first optical path and the second optical path. In step 602 , the optical path length difference refers to the difference in light transmission paths between two optical paths, which determines the interference fringe characteristics.

[0100] The maximum permissible difference corresponding to the temporal stability is the critical value determined by the coherence length of the light source, ensuring that the interference fringes can be resolved.

[0101] In the embodiment of the present application, the optical fiber length of the first optical path is first adjusted using a mechanical displacement platform so that the optical path difference between each wavelength component in the composite optical signal (e.g., 1550nm) and the reference optical signal (1549nm) in the second optical path exceeds its coherence length (for example, the coherence length of the 1550nm light source is 20mm, and the optical path difference is set to 25mm). Secondly, an optical power meter is used to monitor the light intensity balance of the two signals to ensure that the contrast of the interference fringes is maximized. For example, after adjustment, the optical path difference of the 1550nm signal of fiber core A is 25mm, while the optical path difference of the 1555nm signal of fiber core B is 25.05mm, forming a separable fringe pattern.

[0102] 603. Superimpose the output optical signals through an optical signal synthesis element to form spatially distributed interference fringes.

[0103] In step 603, the optical signal combining element refers to a device (such as a fiber coupler or a free-space beam combiner) that realizes the superposition of two optical signals.

[0104] Spatially distributed interference fringes refer to the alternating light intensity distribution of light and dark caused by the optical path difference.

[0105] In this embodiment, the output signals of the first and second optical paths are first introduced into a fiber coupler for superposition. The resulting light is then projected onto the imaging plane through a collimator, forming spatially distributed interference fringes. For example, the 1550nm signal from fiber core A, after superimposing with the 1549nm reference light signal, forms fringes with a spacing of 10μm on the CCD target surface; the 1555nm signal from fiber core B forms fringes with a spacing of 10.2μm. The fringes of each wavelength component are spatially separated, facilitating subsequent independent analysis.

[0106] Here's a specific example: In oil pipeline temperature monitoring, a three-core optical fiber's composite optical signal (1550 / 1555 / 1560 nm) and a reference beam (1549 nm) are split into two optical paths via a beam splitter. The length of the first optical path is adjusted to ensure a 25 mm optical path difference for the 1550 nm component (exceeding its 20 mm coherence length), allowing the three wavelength components to interfere with the reference beam. After being combined via a fiber coupler, a CCD captures three sets of fringes with different spacing (10 μm / 10.2 μm / 10.4 μm), corresponding to the temperature signals of the three fiber cores.

[0107] In summary, steps 601 to 603 achieve spatial separation of multi-wavelength interference fringes through precise optical path difference control to avoid signal crosstalk; the coordinated design of the splitting and synthesis elements ensures high fringe contrast; and the spatially distributed fringes provide clear input for subsequent phase analysis, significantly improving the resolution and anti-interference capability of multi-core optical fiber temperature detection.

[0108] In order to solve the problem of insufficient matching between material properties and measurement accuracy in multi-core optical fiber temperature detection, in some embodiments, step 303 performs temperature-dependent correction on the initial wavelength offset based on parameters of the physical properties of the grating structure, including: 701. Multiply the initial wavelength offset by a temperature sensitivity coefficient of the grating structure material to obtain a multiplication result, wherein the temperature sensitivity coefficient is obtained through experimental calibration and represents the wavelength offset caused by a unit temperature change; In step 701, the temperature sensitivity coefficient refers to a physical parameter that characterizes the response of the grating structure material to temperature changes and is calibrated through a constant temperature experiment.

[0109] The multiplication result refers to the intermediate data after the initial wavelength offset is converted through temperature characteristics.

[0110] In this embodiment, the temperature sensitivity coefficient corresponding to the current grating structure (e.g., 10 pm / °C for a quartz fiber Bragg grating) is first retrieved from the database. The initial wavelength offset (e.g., 15 pm, as detected) is then multiplied by this coefficient (15 pm ÷ 10 pm / °C = 1.5°C) to calculate the temperature change. For example, if the initial wavelength offset of fiber core A at position 20 m is 18 pm, combined with its temperature sensitivity coefficient of 9 pm / °C, a temperature change of 2°C is calculated.

[0111] 702. Perform range verification on the multiplication result according to a preset reflection wavelength range of the grating structure in the etching process to obtain a range verification result. In step 702 , the reflection wavelength range refers to the effective working wavelength band (eg, 1550 nm±2 nm) preset during grating etching.

[0112] The range verification result refers to the inspection standard for determining whether the temperature correction data is within a reasonable physical range.

[0113] In this embodiment, the grating array's reflection wavelength range parameter (e.g., 1548-1552 nm) is first read. The multiplication result (e.g., a 1.5°C shift of 15 pm) is then compared with the allowable range. For example, when the reference wavelength is 1550 nm, the valid shift range is ±2 nm. The verification is performed to determine whether 15 pm (i.e., 0.015 nm) falls within this range.

[0114] 703. When the multiplication result exceeds the range verification result, replace the multiplication result with a boundary value of the range to generate replacement processed data; In step 703, boundary value replacement means that when the data exceeds the physical reasonable range, it is forcibly corrected to the limit value allowed by the system.

[0115] The replaced data refers to the effective wavelength offset after range constraint.

[0116] In this embodiment, out-of-range abnormal data points (e.g., a calculated value of 1552.3 pm at a certain location) are first marked, and then the data is replaced with the nearest boundary value (1552 nm). For example, if the corrected value of 1547.8 pm at position 30 m for fiber core B exceeds the lower limit of 1548 nm, it is replaced with 1548 nm and the correction mark is recorded.

[0117] 704. Record the replaced data as the wavelength offset after temperature correction.

[0118] In step 704, the wavelength offset after temperature correction refers to a valid measurement result that ultimately complies with physical laws and is directly related to actual temperature changes.

[0119] In this embodiment, each data point is first labeled with a location and correction status. Then, the valid data is sorted and stored by core number. For example, the corrected data sequence [12pm, 13pm, 15pm...] for core A at positions 10-50m is stored as the basic temperature distribution data, while abnormal correction points are recorded separately for subsequent analysis.

[0120] Here's a specific example: During high-voltage cable joint monitoring, fiber core A measured an initial wavelength offset of 25 pm at the hotspot (15 m). Using its temperature sensitivity coefficient of 10 pm / °C, a 2.5°C temperature rise was calculated. This corresponding wavelength offset of 25 pm fell within the preset range of 1550 ± 2 nm and was directly stored as valid data. However, at the same location, fiber core B exhibited a calculated offset of 1552.3 pm due to stress interference, exceeding the upper limit of 1552 nm. The system automatically replaced the offset with 1552 pm and triggered an alarm, indicating possible abnormal temperature rise or mechanical damage at this location.

[0121] In summary, steps 701 to 704 ensure that the temperature demodulation results conform to the physical laws of grating sensing through the dual constraints of material characteristic parameters and physical range; the dynamic boundary correction mechanism effectively filters abnormal data; and the standardized data storage format provides reliable input for temperature field reconstruction, significantly improving the physical rationality and engineering practicality of the measurement results.

[0122] Figure 2 The present invention provides a schematic diagram of a multi-point distributed temperature detection system based on a multi-core optical fiber structure. Figure 2 As shown, the system includes: The grating etching module 21 is used to perform grating array etching processing on at least three cores based on the core structure of the multi-core optical fiber to obtain a reflection wavelength range; The signal reflection module 22 is configured to, when an external light source is incident on the multi-core optical fiber, cause the grating structure of each fiber core to reflect the light signal of the corresponding wavelength according to the reflection wavelength range, thereby generating reflected light signals of different wavelength bands; The signal separation module 23 is used to divide the reflected light signals of different wavelength bands into channels using a wavelength splitting device to generate independent channel signals corresponding to each fiber core, and to perform time-series separation on the reflected light signals corresponding to multiple grating structures in the same fiber core using a time-series separation technology to generate discrete reflected signals with discrete time-series distribution; an interference processing module 24 for combining the independent channel signal with the discrete reflection signal, performing interference contrast processing with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset, and performing wavelength offset analysis based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength offset data for each grating structure; The error correction module 25 is used to perform multi-core joint analysis on the difference in the temperature-related wavelength offset data, and to eliminate the bending stress error in combination with the constraint relationship of the fixed core position when the multi-core optical fiber is torsional deformed, so as to generate temperature detection results with independent axial distribution of each core.

[0123] Figure 2 The multi-point distributed temperature detection system based on a multi-core optical fiber structure can be performed Figure 1 The implementation principle and technical effects of the multi-point distributed temperature detection method based on a multi-core optical fiber structure described in the illustrated embodiment will not be elaborated on here. The specific manner in which each module and unit performs operations in the multi-point distributed temperature detection system based on a multi-core optical fiber structure in the above embodiment has been described in detail in the embodiments of the method and will not be elaborated on here.

[0124] In one possible design, Figure 2 The multi-point distributed temperature detection system based on a multi-core optical fiber structure of the embodiment shown can be implemented as a computing device, such as Figure 3 As shown, the computing device may include a storage component 31 and a processing component 32; The storage component 31 stores one or more computer instructions, wherein the one or more computer instructions are called and executed by the processing component 32 .

[0125] The processing component 32 is used for the above Figure 1 The embodiment provides a multi-point distributed temperature detection method based on a multi-core optical fiber structure.

[0126] The processing component 32 may include one or more processors to execute computer instructions to complete all or part of the steps in the above method. Of course, the processing component may also be implemented as one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components to perform the above method.

[0127] The storage component 31 is configured to store various types of data to support operations at the terminal. The storage component can be implemented by any type of volatile or non-volatile memory device, or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk, or optical disk.

[0128] Of course, a computing device may also include other components, such as input / output interfaces, display components, communication components, etc.

[0129] The input / output interface provides an interface between the processing component and the peripheral interface module, which can be an output device, an input device, etc.

[0130] The communication component is configured to facilitate, among other things, wired or wireless communications between the computing device and other devices.

[0131] Among them, the computing device can be a physical device or an elastic computing host provided by a cloud computing platform, etc. In this case, the computing device can refer to a cloud server, and the above-mentioned processing components, storage components, etc. can be basic server resources rented or purchased from the cloud computing platform.

[0132] The present application also provides a computer storage medium storing a computer program, wherein the computer program can achieve the above-mentioned Figure 1 The embodiment shown is a multi-point distributed temperature detection method based on a multi-core optical fiber structure.

[0133] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0134] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0135] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-point distributed temperature detection method based on a multi-core optical fiber structure, characterized in that: include: Based on the core structure of a multi-core optical fiber, at least three cores are etched with a grating array to obtain a reflection wavelength range; When an external light source is incident on the multi-core optical fiber, the grating structure of each core reflects the light signal of the corresponding wavelength according to the reflection wavelength range, thereby generating reflected light signals of different wavelength bands; The reflected light signals of the different wavelength bands are divided into channels by using a wavelength splitting device to generate independent channel signals corresponding to each fiber core, and the reflected light signals corresponding to multiple grating structures in the same fiber core are separated in time sequence by using a time sequence separation technology to generate discrete reflected signals with discrete time sequence distribution; After combining the independent channel signal and the discrete reflection signal, interference contrast processing is performed with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset. The wavelength offset is analyzed based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength offset data for each grating structure. A multi-core joint analysis is performed on the difference in the temperature-related wavelength offset data, and a bending stress error elimination process is performed in combination with the constraint relationship of the core position being fixed during the torsional deformation of the multi-core optical fiber to generate a temperature detection result with independent axial distribution of each core.

2. The method according to claim 1, characterized in that After combining the independent channel signal and the discrete reflection signal, interference contrast processing is performed with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset, including: The independent channel signals from different fiber cores and the discrete reflection signals after time separation in the same fiber core are optically superimposed by an optical signal combining device to form a composite optical signal; The composite optical signal and a reference optical signal of a preset fixed wavelength generate an interference reaction in an interference device, wherein the optical path difference of the interference device is set to generate interference fringes between each wavelength component in the composite optical signal and the reference optical signal; spatially sampling the interference fringes to obtain a light intensity signal including a phase distribution; Calculating the phase difference variation corresponding to each wavelength component according to the intensity variation of adjacent sampling points in the light intensity signal; The phase difference variation is mapped and associated with the reflection wavelength range to determine a phase difference interference signal reflecting the wavelength shift.

3. The method according to claim 2, characterized in that The wavelength shift analysis is performed based on the linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength shift data of each grating structure, including: Establishing a data set of corresponding relationship between phase difference variation and wavelength offset according to a preset reflection wavelength range of the grating structure during etching; Matching the phase difference variation of different wavelength components in the phase difference interference signal with the corresponding relationship data set to determine the initial wavelength offset of each wavelength component; Performing a temperature-dependent correction on the initial wavelength offset based on parameters of the physical characteristics of the grating structure, wherein the parameters of the physical characteristics include a synthetic proportional coefficient of a thermo-optical effect coefficient of a grating structure material; The temperature-dependent wavelength offset of the grating structure is calculated by multiplying the synthesis proportional coefficient by the phase difference variation. The temperature-dependent wavelength shifts of multiple grating structures in the same fiber core are subjected to axial distribution integration processing to generate temperature-dependent wavelength shift data.

4. The method according to claim 1, wherein Performing a multi-core joint analysis on the difference in the temperature-related wavelength shift data, performing bending stress error elimination processing based on the constraint relationship of the core position being fixed during torsional deformation of the multi-core optical fiber, and generating temperature detection results independently distributed in the axial direction of each core, including: Comparing the temperature-related wavelength shift data of different fiber cores at the same axial position to construct a wavelength shift difference data set between fiber cores; Based on the geometric constraint relationship that the relative positions of the cores of the multi-core optical fiber are fixed during torsional deformation, a mapping rule is established between the wavelength offset difference dataset between the cores and the deformation stress distribution; According to the correspondence between the geometric position relationship between the fiber cores and the stress distribution gradient in the mapping rule, a proportional analysis is performed on the wavelength offset difference of each fiber core to calculate the stress influence correction coefficient of each fiber core; Performing a superposition operation on the stress influence correction coefficient and the temperature-related wavelength offset data of the corresponding fiber core to eliminate the coupling interference of deformation stress on the wavelength offset and generate corrected wavelength data; The corrected wavelength data are independently arranged and combined according to the axial position to generate temperature detection results independently distributed in the axial direction of each fiber core.

5. The method according to claim 4, characterized in that The stress influence correction coefficient is superimposed on the temperature-related wavelength offset data of the corresponding fiber core to eliminate the coupling interference of deformation stress on the wavelength offset and generate the corrected wavelength data, including: Converting the stress influence correction coefficient into a wavelength compensation amount through a preset proportional conversion relationship, wherein the value of the wavelength compensation amount is proportional to the absolute value of the correction coefficient and has an opposite sign to the sign of the stress influence correction coefficient; Adding the temperature-related wavelength offset data at the same axial position and the wavelength compensation amount of the corresponding fiber core point by point in the order of the fiber core numbers to obtain added data; Performing validity verification on the added data to obtain a verification result, and when the verification result exceeds a preset reflection wavelength range, truncating the verification result to the nearest boundary value of the range; The nearest boundary value is stored as the corrected wavelength data.

6. The method according to claim 2, characterized in that The composite optical signal and a reference optical signal of a preset fixed wavelength generate an interference reaction in an interference device, wherein the optical path difference of the interference device is set to generate interference fringes between each wavelength component in the composite optical signal and the reference optical signal, including: The composite optical signal and the reference optical signal are respectively fed into a beam splitter of an interference device, and the beam splitter guides the two optical signals into a first optical path and a second optical path respectively; adjusting the optical path length of the first optical path so that the difference between the optical path lengths of the wavelength components in the composite optical signal and the reference optical signal in the second optical path is greater than a maximum allowable difference corresponding to the time stability of the composite optical signal, and generating output optical signals of the first optical path and the second optical path; The output optical signals are superimposed by an optical signal synthesis element to form spatially distributed interference fringes.

7. The method according to claim 3, characterized in that Performing a temperature-dependent correction on the initial wavelength offset based on parameters of the physical characteristics of the grating structure includes: Multiplying the initial wavelength offset by a temperature sensitivity coefficient of the grating structure material to obtain a multiplication result, wherein the temperature sensitivity coefficient is obtained through experimental calibration and represents the wavelength offset caused by a unit temperature change; performing range verification on the multiplication result according to a preset reflection wavelength range of the grating structure in the etching process to obtain a range verification result; When the multiplication result exceeds the range verification result, replacing the multiplication result with a boundary value of the range to generate replacement processed data; The data obtained by the replacement process is recorded as the wavelength shift after temperature correction.

8. A multi-point distributed temperature detection system based on a multi-core optical fiber structure, characterized in that: include: A grating etching module is used to perform grating array etching on at least three cores based on the core structure of a multi-core optical fiber to obtain a reflection wavelength range; A signal reflection module, configured to, when an external light source is incident on the multi-core optical fiber, cause the grating structure of each fiber core to reflect the light signal of the corresponding wavelength according to the reflection wavelength range, thereby generating reflected light signals of different wavelength bands; a signal separation module, configured to divide the reflected light signals of different wavelength bands into channels by using a wavelength splitting device to generate independent channel signals corresponding to each fiber core, and to perform time-series separation on the reflected light signals corresponding to multiple grating structures in the same fiber core by using a time-series separation technology to generate discrete reflected signals with discrete time-series distribution; an interference processing module, configured to combine the independent channel signal and the discrete reflection signal, and then perform interference contrast processing with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength offset; and perform wavelength offset analysis based on a linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure to obtain temperature-dependent wavelength offset data for each grating structure; The error correction module is used to perform multi-core joint analysis on the difference in the temperature-related wavelength offset data, and to eliminate the bending stress error in combination with the constraint relationship of the fixed core position when the multi-core optical fiber is torsional deformed, so as to generate temperature detection results with independent axial distribution of each core.

9. A computing device, characterized in that It includes a processing component and a storage component; the storage component stores one or more computer instructions; the one or more computer instructions are used to be called and executed by the processing component to implement a multi-point distributed temperature detection method based on a multi-core optical fiber structure as described in any one of claims 1 to 7.

10. A computer storage medium, characterized in that A computer program is stored, and when the computer program is executed by a computer, a multi-point distributed temperature detection method based on a multi-core optical fiber structure as described in any one of claims 1 to 7 is implemented.

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