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

Abstract

The application provides a kind of multi-point distributed temperature detection method and system based on 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, each fiber core grating structure reflects light signals of corresponding wavelengths to generate different waveband reflected light signals; wavelength branching devices are used to divide reflected light signal channels to generate independent channel signals of each fiber core, while time sequence separation is carried out on multi-grating signals in the same fiber core to obtain discrete time sequence distributed reflected signals; independent channel signals and discrete reflected signals are combined, and a fixed wavelength reference light signal is used for interference comparison to generate phase difference interference signals reflecting wavelength shift, and wavelength shift is analyzed to obtain temperature related wavelength shift data; by analyzing stress error elimination under deformation constraint, temperature detection results are output. The technical solution provided by the application improves the accuracy of distributed temperature detection.

Description

Technical Field

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

[0002] In industrial settings such as petrochemicals and power transmission, real-time, high-precision monitoring of temperature distribution in long-distance pipelines or equipment is required. Traditional point-based temperature measurement technologies are insufficient to meet the needs of distributed measurement, while multi-core optical fibers, with their spatial resolution and electromagnetic interference resistance, have become an ideal temperature sensing medium.

[0003] The more advanced solutions currently available use single-core optical fibers combined with Raman scattering and optical frequency domain reflection technologies to measure temperature by analyzing the frequency shift of backscattered light.

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

[0005] This 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] Firstly, this application provides a multi-point distributed temperature detection method based on a multi-core optical fiber structure, including:

[0007] Based on the fiber core structure of multi-core optical fiber, at least three fiber cores are etched with a grating array to obtain the reflection wavelength range;

[0008] 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, generating reflected light signals of different bands.

[0009] The reflected light signals of different wavelength bands are divided into channels using a wavelength splitting device to generate independent channel signals corresponding to each fiber core. At the same time, the reflected light signals corresponding to multiple grating structures in the same fiber core are separated in time to generate discrete reflected signals with discrete time distribution.

[0010] After merging the independent channel signal and the discrete reflection signal, the signal is compared with a reference light signal of a preset fixed wavelength to generate a phase difference interference signal that reflects the wavelength offset. The wavelength offset is then 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 the temperature-related wavelength offset data of each grating structure.

[0011] The differences in the temperature-related wavelength offset data are analyzed by multiple fiber cores. The bending stress error is eliminated by combining the constraint relationship of fixed fiber core position during the torsional deformation of the multi-core optical fiber, and the temperature detection results of each fiber core are generated with independent axial distribution.

[0012] Optionally, the independent channel signal and the discrete reflection signal are combined and then subjected to interference comparison processing with a reference light signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength shift, including:

[0013] The independent channel signals from different fiber cores and the discrete reflected signals that have been time-separated within the same fiber core are combined by an optical signal combining device to form a composite optical signal.

[0014] The composite optical signal and the reference optical signal with a preset fixed wavelength interfere with each other in the interference device, wherein the optical path difference of the interference device is set to produce interference fringes between each wavelength component of the composite optical signal and the reference optical signal.

[0015] Spatial sampling is performed on the interference fringes to obtain an intensity signal containing the phase distribution;

[0016] Based on the intensity changes of adjacent sampling points in the light intensity signal, the phase difference change corresponding to each wavelength component is calculated.

[0017] The phase difference change is mapped and correlated with the reflected wavelength range to determine the phase difference interference signal that reflects the wavelength offset.

[0018] Optionally, 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-related wavelength shift data for each grating structure, including:

[0019] Based on the preset reflection wavelength range of the grating structure during etching, a dataset of the correspondence between phase difference change and wavelength offset is established.

[0020] The phase difference change of different wavelength components in the phase difference interference signal is matched with the corresponding relationship dataset to determine the initial wavelength offset of each wavelength component;

[0021] Based on the parameters of the physical properties of the grating structure, the initial wavelength offset is corrected by temperature correlation, wherein the parameters of the physical properties include the synthesis ratio coefficient of the thermo-optic effect coefficient of the grating structure material.

[0022] The temperature-induced wavelength shift of the grating structure is calculated by multiplying the synthesis scaling factor with the phase difference change.

[0023] The temperature-dependent wavelength offset of multiple grating structures within the same fiber core is integrated through axial distribution processing to generate temperature-related wavelength offset data.

[0024] Optionally, multi-core joint analysis is performed on the differences in the temperature-related wavelength offset data. Bending stress error elimination processing is then performed, combining this with the constraint relationship of fixed core positions during torsional deformation of the multi-core optical fiber, to generate temperature detection results with independent axial distribution for each core, including:

[0025] The temperature-related wavelength shift data of different fiber cores at the same axial position are compared to construct a wavelength shift difference dataset between fiber cores;

[0026] Based on the geometric constraint relationship that the relative positions of the fiber cores are fixed during torsional deformation of the multi-core optical fiber, a mapping rule between the wavelength offset difference dataset between the fiber cores and the deformation stress distribution is established.

[0027] Based on the correspondence between the geometric positional relationship between fiber cores and the stress distribution gradient in the mapping rule, a proportional analysis is performed on the wavelength shift difference of each fiber core, and the stress influence correction coefficient of each fiber core is calculated.

[0028] The stress influence correction coefficient is superimposed with 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.

[0029] The corrected wavelength data are independently arranged and combined according to the axial position to generate temperature detection results that are independently distributed along the axial direction of each fiber core.

[0030] Optionally, the stress influence correction coefficient is superimposed with the temperature-related wavelength shift data of the corresponding fiber core to eliminate the coupling interference of deformation stress on the wavelength shift, generating corrected wavelength data, including:

[0031] The stress influence correction coefficient is converted 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 the sign is opposite to that of the stress influence correction coefficient;

[0032] According to the fiber core numbering sequence, the temperature-related wavelength offset data at the same axial position is added point by point to the wavelength compensation amount of the corresponding fiber core to obtain the added data;

[0033] The validity of the summed data is verified to obtain a verification result. When the verification result exceeds the preset reflection wavelength range, the verification result is truncated to the nearest boundary value of the range.

[0034] The most recent boundary value is stored as corrected wavelength data.

[0035] Optionally, the composite optical signal and a reference optical signal with a preset fixed wavelength interfere in an interferometer, wherein the optical path difference of the interferometer is set to cause each wavelength component of the composite optical signal to produce interference fringes with the reference optical signal, including:

[0036] The composite optical signal and the reference optical signal are respectively fed into the beam splitter of the interferometer, and the beam splitter guides the two optical signals into the first optical path and the second optical path, respectively.

[0037] Adjust the optical path length of the first optical path so that the difference between the optical path length 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, and generate the output optical signals of the first optical path and the second optical path;

[0038] The output optical signals are superimposed by an optical signal synthesizing element to form spatially distributed interference fringes.

[0039] Optionally, based on parameters of the physical properties of the grating structure, a temperature-related correction is performed on the initial wavelength offset, including:

[0040] The initial wavelength shift is multiplied by the temperature sensitivity coefficient of the grating structure material to obtain the multiplication result, wherein the temperature sensitivity coefficient is obtained through experimental calibration and represents the wavelength shift caused by a unit temperature change.

[0041] Based on the preset reflection wavelength range of the grating structure in the etching process, the multiplication result is verified to obtain the range verification result;

[0042] When the result of the multiplication operation exceeds the range verification result, the boundary value of the range is used to replace the result of the multiplication operation, and replacement processing data is generated;

[0043] The data from the replacement process is recorded as the temperature-corrected wavelength offset.

[0044] Secondly, this application provides a multi-point distributed temperature detection system based on a multi-core optical fiber structure, comprising:

[0045] A grating etching module is used for fiber core structures based on multi-core optical fibers to perform grating array etching on at least three fiber cores to obtain the reflection wavelength range;

[0046] The signal reflection module is used to generate reflected light signals of different bands by having the grating structure of each fiber core reflect light signals of the corresponding wavelength according to the reflection wavelength range when an external light source is incident on the multi-core optical fiber.

[0047] The signal separation module is used to divide the reflected light signals of different wavelength bands into channels using a wavelength splitting device, generating independent channel signals corresponding to each fiber core. At the same time, it uses time-separation technology to separate the reflected light signals corresponding to multiple grating structures in the same fiber core, generating discrete reflection signals with discrete time-separation distribution.

[0048] The interference processing module is used to merge the independent channel signal and the discrete reflection signal, and then perform interference comparison processing with the reference light signal with a preset fixed wavelength to generate a phase difference interference signal that reflects the wavelength offset. Based on the linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure, wavelength offset analysis is performed to obtain the temperature-related wavelength offset data of each grating structure.

[0049] The error correction module is used to perform multi-core joint analysis on the differences in the temperature-related wavelength offset data, and to perform bending stress error elimination processing in combination with the constraint relationship that the core position is fixed during the torsional deformation of the multi-core optical fiber, so as to generate temperature detection results that are independently distributed along the axis of each core.

[0050] Thirdly, this application provides a computing device, including a processing component and a storage component; the storage component stores one or more computer instructions; the one or more computer instructions are invoked 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.

[0051] Fourthly, this application provides a computer storage medium storing a computer program, which, when executed by a computer, implements a multi-point distributed temperature detection method based on a multi-core optical fiber structure as described in the first aspect.

[0052] In this embodiment, based on the fiber core structure of a multi-core optical fiber, at least three fiber 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 fiber core reflects light signals of corresponding wavelengths according to the reflection wavelength range, generating reflected light signals of different bands. A wavelength splitter is used to divide the reflected light signals of different bands into channels, generating independent channel signals corresponding to each fiber core. Simultaneously, a timing separation technique is used to perform timing separation on the reflected light signals corresponding to multiple grating structures in the same fiber core, generating discrete reflection signals with discrete timing distributions. After the independent channel signal is merged with the discrete reflection signal, it is subjected to interference comparison processing 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 for each grating structure. The differences in the temperature-related wavelength offset data are analyzed by multi-core joint analysis. The bending stress error is eliminated by combining the constraint relationship of the fixed position of the fiber core during the torsional deformation of the multi-core fiber, and the temperature detection results of each fiber core are generated with independent axial distribution.

[0053] The technical solution of this application has the following beneficial effects: it realizes 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; it generates temperature-related characteristic optical signals through precise control of wavelength range, establishing a temperature-wavelength mapping relationship; it uses wavelength division multiplexing to achieve spatial dimension (between fiber cores) separation and uses temporal separation to achieve temporal dimension (within fiber cores) separation, significantly improving signal capacity; it converts minute wavelength shifts into measurable phase differences through interference comparison, greatly improving temperature detection sensitivity; and it utilizes the spatial constraint relationship of multiple fiber cores to decouple temperature and stress cross-sensitivity, improving measurement accuracy by more than 3 times.

[0054] Furthermore, a mixed signal containing multiple wavelength components is formed by superimposing optical power. After generating resolvable interference fringes through an interferometer, the light intensity signal obtained from spatial sampling is converted into a phase difference change and mapped to a wavelength offset. Subsequently, based on the reflection wavelength range preset by the etching process and the thermo-optical properties of the material, temperature correlation correction and axial integration processing are used to finally generate temperature data that eliminates stress interference. This scheme, through the coordinated processing of wavelength division / time division multiplexing and interferometric demodulation, improves the accuracy of temperature measurement in multi-core optical fibers while maintaining spatial resolution, and also enhances the resistance to bending interference.

[0055] These or other aspects of this application will become more apparent in the following description of the embodiments. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This paper presents a flowchart of a multi-point distributed temperature detection method based on a multi-core optical fiber structure provided in this application.

[0058] Figure 2 This paper presents a schematic diagram of a multi-point distributed temperature detection system based on a multi-core optical fiber structure provided in this application.

[0059] Figure 3 A schematic diagram of the structure of a computing device provided in this application is shown. Detailed Implementation

[0060] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0061] In some of the processes described in the specification, claims, and accompanying drawings of this application, multiple operations appearing in a specific order are included. However, it should be clearly understood that these operations may not be executed in the order they appear herein, or may be executed in parallel. The operation numbers, such as 101, 102, etc., are merely used to distinguish different operations and do not themselves represent any execution order. Furthermore, these processes may include more or fewer operations, and these operations may be executed sequentially or in parallel. It should be noted that the descriptions such as "first," "second," etc., in this document are used to distinguish different messages, devices, modules, etc., and do not represent a chronological order, nor do they limit "first" and "second" to different types.

[0062] Existing distributed fiber optic temperature sensing technologies primarily employ single-core optical fibers combined with Raman or Brillouin scattering principles. While enabling long-distance measurements, these technologies suffer from three key drawbacks: First, temperature measurement schemes based on scattering effects exhibit low signal-to-noise ratios, resulting in limited temperature resolution. Second, single-core structures cannot distinguish between the cross-sensitivity of temperature and strain, leading to significantly increased 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 demands of industrial applications for low cost and high robustness. These shortcomings essentially stem from the insufficient signal capacity and limited physical dimensions of single-core sensing structures, making it impossible to simultaneously achieve high-precision measurement and multi-parameter decoupling.

[0063] To address the aforementioned issues, this application proposes a multi-point distributed temperature detection method based on a multi-core optical fiber structure. Its innovation lies in: constructing a three-dimensional encoded sensing network (spatial, wavelength, and temporal) by etching FBG arrays with different wavelength ranges in each core of the multi-core optical fiber; utilizing wavelength division multiplexing (WDM) to achieve parallel acquisition of multi-core signals, and combining it with time division multiplexing (TDM) to improve the spatial resolution of multiple measurement points within a single core; and finally achieving precise separation of temperature and stress through multi-core interferometric demodulation and collaborative error correction. This method significantly improves the signal-to-noise ratio and reduces cross-sensitivity errors by utilizing the geometric constraints of multi-core optical fibers. Compared to traditional solutions, it reduces system cost while maintaining spatial resolution, fundamentally solving the three core problems of insufficient measurement accuracy, poor anti-interference capability, and high cost in existing technologies. It is particularly suitable for high-reliability temperature monitoring in complex industrial environments such as oil pipelines and high-voltage cables.

[0064] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0065] Figure 1 This application provides a flowchart of a multi-point distributed temperature detection method based on a multi-core optical fiber structure, as shown in the embodiments of this application. Figure 1 As shown, the method includes:

[0066] 101. Based on the fiber core structure of a multi-core optical fiber, at least three fiber cores are etched with a grating array to obtain the reflection wavelength range;

[0067] In this step, multi-core fiber is a special fiber structure containing multiple independent cores, each capable of transmitting optical signals independently. Grating array etching is performed using processes such as ultraviolet lasers to create periodic refractive index modulation structures within the fiber cores, forming a series of fiber Bragg gratings. The reflection wavelength range refers to the specific wavelength range of optical signals that each grating structure can reflect; gratings in different fiber cores are designed to reflect signals in different wavelength bands.

[0068] In this embodiment, a suitable multi-core optical fiber is first selected, and the number of fiber cores to be etched is determined. Then, ultraviolet laser phase masking is used to perform grating etching on the selected fiber cores. During the etching process, by precisely controlling the laser parameters and exposure time, it is ensured that the grating array of each fiber core has a specific reflection wavelength range, and that the reflection bands of adjacent fiber cores do not overlap. After etching is completed, a spectral analysis device is used to verify the reflection characteristics of each fiber core grating to ensure that the design requirements are met.

[0069] In a practical case, grating arrays with center wavelengths of 1550nm, 1555nm, and 1560nm were etched on the three cores of a three-core optical fiber, with each reflection band spaced 5nm apart and the reflection bandwidth controlled within 0.3nm.

[0070] 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, generating reflected light signals of different bands.

[0071] In this step, the external light source refers to a broadband light source capable of covering all grating reflection bands. Different bands of reflected light signals refer to the selective reflection of light signals within a specific wavelength range by the grating structure of each fiber core according to its reflection characteristics.

[0072] In this embodiment, a broadband light source is injected into a multi-core optical fiber through an optical fiber circulator. The spectral range of the light source needs to completely cover the reflection bands of all fiber core gratings. When the optical signal is transmitted in the optical fiber, the grating structure of each fiber core selectively reflects the corresponding optical signal band according to its preset reflection wavelength range, while the optical signal of other wavelengths continues to be transmitted. The reflected optical signal is output through another port of the circulator and enters the subsequent signal processing unit.

[0073] 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 optical signals in the 1550nm band, fiber core B reflects optical signals in the 1555nm band, and fiber core C reflects optical signals in the 1560nm band. These reflected optical signals are output to the wavelength division multiplexing device through a circulator.

[0074] 103. The wavelength splitter is used to divide the reflected light signals of different wavelength bands into channels to generate independent channel signals corresponding to each fiber core. At the same time, the timing separation technology is used to separate the reflected light signals corresponding to multiple grating structures in the same fiber core to generate discrete reflection signals with discrete timing distribution.

[0075] In this step, a wavelength splitter is an optical device capable of separating 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. Timing separation technology is a method of signal separation achieved by controlling the pulse characteristics of the light source and the detection time window. Discrete reflection signals refer to the sequence of reflected light pulses arranged in chronological order after timing separation.

[0076] In this embodiment, the reflected light signals from each fiber core are first input to a wavelength splitter, which separates the signals from different fiber cores into independent output channels based on the wavelength. Then, the light signal in each channel is 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 reflection signals.

[0077] Continuing with the above example, arrayed waveguide gratings are used to guide optical signals of 1550nm, 1555nm, and 1560nm into three independent channels. Then, a 100ns optical pulse is applied to each channel. The reflected pulses of the gratings at different positions are detected by time-domain reflectometry, and the signals of each grating are distinguished based on the arrival time of the pulses.

[0078] 104. After merging the independent channel signal and the discrete reflection signal, perform interference comparison processing with the reference light signal of a preset fixed wavelength to generate a phase difference interference signal that reflects the wavelength offset. Then, perform wavelength offset 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 the temperature-related wavelength offset data of each grating structure.

[0079] 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 refers to the information reflecting the phase change of the optical signal obtained by measuring with an interferometer. The linear relationship of temperature change describes the law of change of the grating reflection wavelength with temperature.

[0080] In this embodiment, the separated fiber core optical signals are first input into an interferometer along with a reference optical signal. By adjusting the optical path length difference of the interferometer, clear interference fringes are generated between the composite optical signal and the reference optical signal. Then, a photodetector array is used to collect the intensity distribution of the interference fringes. By analyzing the phase change characteristics of the fringes, the wavelength shift of each grating reflection signal is calculated. Based on a pre-calibrated temperature sensitivity coefficient, the wavelength shift is converted into a corresponding temperature change value.

[0081] Continuing with the above case, the 1550nm fiber core A signal and the 1549nm reference light are interfered with in an interferometer. The wavelength shift of 0.1nm is calculated by measuring the movement of the interference fringes, and the temperature change of 10℃ is obtained based on the sensitivity coefficient of 10pm / ℃.

[0082] 105. Perform multi-core joint analysis on the differences in the temperature-related wavelength offset data, and combine the constraint relationship of fixed core position during the torsional deformation of the multi-core optical fiber to perform bending stress error elimination processing, and generate temperature detection results with independent axial distribution of each core.

[0083] In this step, the core position fixation constraint refers to the characteristic that the relative positional relationship between the individual cores of a multi-core optical fiber remains unchanged during deformation. Bending stress error elimination refers to using the measurement data from multiple cores to mutually correct each other and eliminate measurement errors caused by fiber bending.

[0084] In this embodiment, temperature-related wavelength offset data for each fiber core at the same measurement location are first collected, and the differences between the data for each fiber core are analyzed. Based on the structural characteristics of multi-core optical fibers, a mathematical model of the fiber core position and stress distribution is established. The error component caused by bending stress in the measurement data of each fiber core is calculated using this model, and then the original measurement data is corrected to obtain the true temperature data after eliminating the influence of stress.

[0085] Continuing with the above case, when the temperature data of the three fiber cores at the same location are found to be different, the influence of 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.

[0086] In summary, steps 101 to 105 involve fabricating a specially designed grating array on a multi-core optical fiber, utilizing wavelength division multiplexing (WDM) and time division multiplexing (TDM) techniques to achieve signal separation, employing interferometry to improve detection sensitivity, and finally eliminating measurement errors based on the spatial constraint relationship of the multi-core fibers, thus forming a complete distributed temperature detection scheme. This achieves high spatial resolution temperature distribution measurement, effectively overcoming the problems of signal crosstalk and stress cross-sensitivity in traditional methods, improving measurement accuracy and reliability, and making it suitable for temperature monitoring needs in various complex environments.

[0087] To address the issues of signal coupling interference and insufficient demodulation accuracy in multi-core fiber temperature detection, in some embodiments, step 104 involves merging the independent channel signal and the discrete reflection signal, and then performing interference comparison processing with a reference optical signal of a preset fixed wavelength to generate a phase difference interference signal reflecting the wavelength shift, including:

[0088] 210. The independent channel signals from different fiber cores and the discrete reflected signals after time separation within the same fiber core are combined by an optical signal combining device to form a composite optical signal;

[0089] In step 201, the optical signal combining device refers to an optical device (such as an optical fiber coupler) that achieves linear superposition of optical power, used to fuse multiple input signals. A composite optical signal refers to a composite optical signal containing multiple fiber core wavelength components and timing characteristics.

[0090] In this embodiment, the wavelength division multiplexed independent channel signals (fiber cores A / B / C corresponding to 1550 / 1555 / 1560nm signals respectively) and the time-separated discrete reflection signals within the same fiber core (such as the pulse signals of the three gratings in fiber core A) are first input into the fiber coupler. The coupler performs optical power superposition on each signal, preserving the amplitude and phase information of each wavelength component. For example, the 1550nm continuous wave signal of fiber core A and the pulse reflection signals of its three gratings are combined into a single composite optical signal, forming a spatiotemporally interwoven composite optical field.

[0091] 202. The composite optical signal and a reference optical signal with a preset fixed wavelength interfere in an interference device, wherein the optical path difference of the interference device is set to cause each wavelength component in the composite optical signal to produce interference fringes with the reference optical signal;

[0092] In step 202, the interference device refers to an optical structure that generates an optical path difference (such as a Mach-Zehnder interferometer). Setting the optical path difference means ensuring that the optical path difference between different wavelength components and the reference light exceeds their coherence length, thereby ensuring that the interference fringes are resolvable.

[0093] In this embodiment, the composite optical signal and the reference optical signal (such as a 1549nm narrow-linewidth laser) are respectively input into two optical paths of the interferometer. By adjusting the mechanical displacement device of the reference arm, the optical path difference between each wavelength component (such as 1550nm, 1555nm) in the composite optical signal and the reference light is made greater than its coherence length. For example, the optical path difference of the 1550nm component is set to 25mm (corresponding to its coherence length of 20mm). At this time, the wavelength component interferes with the reference light to form fringes with stable spacing, while the 1555nm component forms fringes with slightly different spacing due to the different optical path difference.

[0094] 203. Spatial sampling of the interference fringes to obtain an intensity signal containing the phase distribution;

[0095] In step 203, spatial sampling refers to acquiring light intensity values ​​at fixed intervals along the direction of the interference fringes. The light intensity signal is a discrete data sequence containing the interference phase distribution of each wavelength component.

[0096] In this embodiment, a linear CCD detector is used to scan along the direction of the interference fringes, with a sampling interval less than 1 / 4 of the minimum fringe period (e.g., a 10μm fringe period corresponds to a 2.5μm sampling interval). The detector records the light intensity value at each sampling point, forming a light intensity distribution curve containing phase gradient information. For example, interference fringes with 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.

[0097] 204. Based on the intensity changes of adjacent sampling points in the light intensity signal, calculate the phase difference change corresponding to each wavelength component;

[0098] In step 204, the phase difference change refers to the phase difference value reflected by the change in light intensity of adjacent sampling points, which is linearly related to the wavelength offset.

[0099] In this embodiment, the light intensity signal is differentially calculated. Based on the ratio of the light intensity variation amplitude (ΔI) of adjacent sampling points to the average light intensity (I0), and combined with the interference equation ΔI / I0=sin(Δφ), the local phase difference change Δφ is solved. For example, the differential calculation result of a certain light intensity sequence is Δφ=0.8rad, indicating that there is a phase shift caused by temperature at that location.

[0100] 205. Map and associate the phase difference change with the reflection wavelength range to determine the phase difference interference signal that reflects the wavelength offset.

[0101] In step 205, mapping association refers to converting the phase difference into a physical quantity through the phase difference-wavelength offset correspondence established by calibration.

[0102] In this embodiment, based on the pre-calibrated correspondence between the reflection wavelength range and the phase difference change, the phase difference change of each wavelength component is converted into the actual wavelength offset, and finally a phase difference interference signal containing the wavelength offset information of each fiber core is generated.

[0103] Here is a specific example:

[0104] In the oil pipeline monitoring scenario, the cores A (1550nm), B (1555nm), and C (1560nm) of the three-core optical fiber are combined into a composite optical signal in step 210. This signal, along with the 1549nm reference light, forms three sets of fringes with different spacing in an interferometer (step 202). A linear CCD is used to sample at 2.5μm intervals (step 203), and the phase differences between cores A / B / C are calculated to be 0.8 / 0.82 / 0.85 rad, respectively (step 204). Finally, these phase differences are mapped to wavelength offsets of 12 / 12.3 / 12.75 pm (step 205), and the output is a phase difference interference signal containing the axial temperature distribution of the pipeline.

[0105] In summary, steps 201 to 205, through the coordinated design of signal merging and interference processing, achieved parallel demodulation and high-precision phase extraction of multi-fiber core signals; the interference fringe separation technology based on optical path difference control effectively avoided multi-wavelength crosstalk; and the calibration mapping mechanism accurately converted phase changes into physical quantities, significantly improving the reliability and spatial resolution of temperature detection in complex environments.

[0106] To address the issues of cross-sensitivity error and insufficient data integration in multi-core fiber temperature detection, some embodiments further include step 104 of 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 for each grating structure, including:

[0107] 301. Based on the preset reflection wavelength range of the grating structure during etching, establish a dataset of the correspondence between the phase difference change and the wavelength offset;

[0108] In step 301, the reflection wavelength range refers to the specific reflection band preset during etching of the grating array (e.g., 1550-1555nm). The corresponding dataset is a set of mapping relationships between phase difference change and wavelength offset established in the indexing experiment.

[0109] In this embodiment, a temperature calibration experiment is first performed on the etched grating array using a tunable laser, recording the phase difference change and corresponding wavelength offset of each grating at different temperatures. Next, the data is categorized and stored according to fiber core number, axial position, and reflection wavelength. Then, a multidimensional lookup table is established for the reflection wavelength range and phase difference change; for example, a 1550nm grating corresponds to a phase difference of 0.5rad at a 10℃ temperature rise. Finally, the calibration data is integrated into the demodulation system database to form a real-time queryable dataset.

[0110] 302. Match the phase difference change of different wavelength components in the phase difference interference signal with the corresponding relationship dataset to determine the initial wavelength offset of each wavelength component;

[0111] In step 302, the initial wavelength offset refers to the original wavelength offset value without temperature correction, which includes stress interference components.

[0112] In this embodiment, the phase difference change of each wavelength component is first extracted from the phase difference interference signal; then, matching records with the same reflection wavelength range are searched in the corresponding relationship dataset; next, the initial wavelength offset corresponding to the current phase difference is determined by linear interpolation (e.g., 0.8 rad is mapped to 12 pm); finally, the offsets of each wavelength component are classified according to the fiber core number to generate an initial wavelength offset list.

[0113] 303. Based on the parameters of the physical properties of the grating structure, the initial wavelength offset is corrected by temperature correlation, wherein the parameters of the physical properties include the synthesis ratio coefficient of the thermo-optic effect coefficient of the grating structure material;

[0114] In step 303, the composite proportionality coefficient refers to the temperature sensitivity coefficient that combines the thermal expansion coefficient and the thermo-optic effect, characterizing the wavelength shift caused by a unit temperature change.

[0115] In this embodiment, the grating material properties (such as the thermal expansion coefficient of quartz fiber being 0.55 × 10⁻⁶) are first considered. The temperature sensitivity coefficient is determined by an isothermal experiment using the packaging process parameters (such as the elastic modulus of the coating layer). Next, the coefficients of each grating are stored in the database according to their axial positions. Then, the synthesis ratio coefficient (such as 10 pm / ℃) corresponding to the current grating is retrieved from the database. Finally, the coefficient is correlated with the initial wavelength offset.

[0116] 304. The temperature-induced wavelength shift of the grating structure is calculated by using the product relationship between the synthesis scaling factor and the phase difference change.

[0117] In step 304, the temperature-induced wavelength offset refers to the wavelength offset value caused solely by temperature changes after stress interference has been eliminated.

[0118] In this embodiment, the initial wavelength offset (e.g., 12 pm) is first divided by the synthesis scaling factor (10 pm / ℃) to obtain the original temperature change (1.2℃); then, based on the linear relationship of the temperature response of the grating material, the wavelength offset under pure temperature action is calculated in reverse (1.2℃×10 pm / ℃=12 pm); finally, it is verified whether the calculation result is within the allowable range of the grating reflection wavelength (e.g., 1550±2nm), and if it exceeds the range, it is corrected according to the boundary value.

[0119] 305. The temperature-dependent wavelength offset of multiple grating structures within the same fiber core is integrated and distributed axially to generate temperature-related wavelength offset data.

[0120] In step 305, the axial distribution integration process refers to sorting and associating the temperature-affected wavelength offsets of multiple gratings within the same fiber core according to their spatial positions.

[0121] In this embodiment, the wavelength offset of the temperature effect is first sorted according to the axial position coordinates of the grating (e.g., 10cm, 20cm, 30cm from the starting end); then, the adjacent grating data is smoothed and filtered according to the continuous deformation characteristics of the optical fiber; next, the processed data is encapsulated into an independent temperature distribution sequence according to the fiber core number; finally, the multi-fiber core data is synchronously output to the visualization terminal.

[0122] Here is a specific example:

[0123] In high-voltage cable temperature monitoring, three gratings were etched into fiber core A of a three-core optical fiber (positions 10 / 20 / 30m, reflection wavelength 1550nm), and its temperature sensitivity coefficient was stored centrally in the calibration data as 10pm / ℃. During detection, the measured phase difference changes were 0.8 / 0.85 / 0.9rad, with initial wavelength offsets of 12 / 12.75 / 13.5pm. After correction using a proportional gain, the calculated temperature-affected wavelength offsets were 12 / 12.75 / 13.5pm. Sorting by position, the axial temperature distribution data for fiber core A was generated, showing an abnormal temperature increase of 1.275℃ in the middle section (20m) of the cable.

[0124] 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-core collaborative analysis significantly improves measurement reliability under complex deformation environments, providing high-precision temperature distribution data for industrial equipment safety monitoring.

[0125] To address the measurement distortion caused by bending stress interference in multi-core fiber temperature detection, some embodiments perform multi-core joint analysis on the differences in the temperature-related wavelength offset data in step 105. This analysis, combined with the constraint relationship of fixed core positions during torsional deformation of the multi-core fiber, eliminates bending stress errors, generating temperature detection results with independent axial distribution for each core.

[0126] 401. Compare the temperature-related wavelength shift data of different fiber cores at the same axial position to construct a wavelength shift difference dataset between fiber cores;

[0127] In step 401, the wavelength offset difference dataset between fiber cores refers to the set of differences in temperature-related wavelength offsets of different fiber cores at the same axial position, reflecting the measurement deviation caused by bending stress.

[0128] In this embodiment, the temperature-related wavelength offset of each fiber core at the same axial position is first obtained (e.g., fiber core A is 12 pm, fiber core B is 15 pm, and fiber core C is 18 pm); then the offset difference between each fiber core is calculated (e.g., A and B differ by 3 pm, B and C differ by 3 pm, and C and A differ by 6 pm); then the difference data is classified and stored according to the fiber axial position coordinates; finally, a multidimensional dataset containing position, fiber core number, and difference value is formed.

[0129] 402. Based on the geometric constraint relationship that the relative positions of the fiber cores are fixed during torsional deformation of the multi-core optical fiber, establish a mapping rule between the wavelength offset difference dataset between the fiber cores and the deformation stress distribution.

[0130] In step 402, the mapping rule for deformation stress distribution refers to the stress-wavelength offset relationship model established based on the multi-core fiber geometry, which reflects the correlation between the fiber core position and the stress gradient.

[0131] In this embodiment, firstly, a mathematical model of the spatial coordinates of the fiber cores and the stress distribution is established based on the fiber core arrangement (such as triangular symmetry) of the multi-core optical fiber; secondly, the wavelength shift difference of each fiber core under different degrees of bending is measured through calibration experiments; then, the experimental data is fitted into a linear relationship equation between stress gradient and shift difference; finally, the equation parameters are integrated into the demodulation system to form a mapping rule library.

[0132] 403. Based on the correspondence between the geometric positional relationship between fiber cores and the stress distribution gradient in the mapping rule, perform a proportional analysis on the wavelength shift difference of each fiber core, and calculate the stress influence correction coefficient of each fiber core.

[0133] In step 403, the stress influence correction coefficient refers to the weight that characterizes the influence of bending stress on the wavelength offset, and is calculated through geometric positional relationships.

[0134] In this embodiment, the stress-offset relationship equation corresponding to the current fiber deformation mode is first called from the mapping rule base; then, the stress gradient distribution is calculated based on the fiber core spacing (e.g., the spacing between fiber cores A and B is 125 μm); next, the correction coefficient of each fiber core is determined by the scaling factor conversion (e.g., a unit stress gradient corresponds to a wavelength offset of 0.1 pm); finally, a correspondence table between fiber core number and correction coefficient is generated (e.g., fiber core A coefficient -0.2, fiber core B coefficient +0.1, fiber core C coefficient +0.1).

[0135] 404. The stress influence correction coefficient is superimposed with 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.

[0136] In step 404, the corrected wavelength data refers to the wavelength offset after eliminating stress interference, which only reflects the true value of temperature change.

[0137] In this embodiment, the temperature-related wavelength offset (e.g., fiber core A refers to 12 pm) and its corresponding correction coefficient (-0.2) are read first; then the offset is multiplied by the correction coefficient to obtain the compensation amount (12 pm × (-0.2) = -2.4 pm); then the compensation amount is added to the original offset (12 pm + (-2.4 pm) = 9.6 pm); finally, it is verified whether the corrected data is within the allowable range of grating reflection wavelength. If it exceeds the range, it is truncated to the boundary value.

[0138] 405. The corrected wavelength data are independently arranged and combined according to the axial position to generate temperature detection results that are independently distributed along the axial direction of each fiber core.

[0139] In step 405, the axially independently distributed temperature detection results refer to the independent temperature data of each fiber core arranged according to the axial position of the fiber, eliminating cross-interference between fiber cores.

[0140] In this embodiment, the corrected wavelength data is first sorted according to the axial position coordinates (e.g., 0m, 10m, 20m); then the data is grouped according to the fiber core number (e.g., fiber core group A, group B, group C); then each group of data is converted into a temperature value (e.g., a wavelength offset of 9.6pm corresponds to a temperature rise of 0.96℃); finally, an independent temperature distribution curve for each fiber core is output.

[0141] Here is a specific example:

[0142] In submarine cable monitoring, the temperature-related wavelength offsets at a certain axial position of the cores A / B / C (spacing 200μm) of a seven-core optical fiber were measured to be 15 / 18 / 21 pm. After constructing a difference dataset (A and B differ by 3 pm, B and C differ by 3 pm), the stress gradient was calculated based on a triangular core arrangement model, and the correction coefficients were determined to be -0.3 / +0.15 / +0.15. The corrected data are 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 according to the axial position, showing that there is localized overheating in the middle of the cable (core B).

[0143] In summary, steps 401 to 405 accurately separate the temperature and stress coupling effects through multi-core difference analysis and geometric constraint modeling; the dynamic correction mechanism effectively eliminates bending deformation interference; and the axial independent data output provides a highly reliable temperature distribution map, significantly improving the accuracy and practicality of fiber optic temperature measurement under complex working conditions.

[0144] To address the issue of data distortion caused by stress interference in multi-core fiber temperature detection, in some embodiments, step 404 involves superimposing the stress influence correction coefficient with 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, including:

[0145] 501. The stress influence correction coefficient is converted 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 the sign is opposite to that of the stress influence correction coefficient;

[0146] In step 501, the wavelength compensation amount refers to the wavelength adjustment value converted according to the stress influence correction coefficient, which is used to offset the measurement deviation caused by stress.

[0147] The preset proportional conversion relationship refers to the linear correspondence between the stress correction coefficient and the wavelength compensation amount established through calibration experiments.

[0148] In this embodiment, the stress influence correction coefficient stored in the database is first called (e.g., the correction coefficient for fiber core A is -0.2). The wavelength compensation is calculated according to a preset proportional conversion relationship (e.g., a unit correction coefficient corresponds to a 5pm compensation). The value is the absolute value of the correction coefficient multiplied by a proportional factor (0.2 × 5pm = 1pm), with the sign opposite to the correction coefficient (-0.2 corresponds to +1pm). For example, the correction coefficient of fiber core A, -0.2, is converted to a compensation of +1pm, and the correction coefficient of fiber core B, +0.1, is converted to a compensation of -0.5pm.

[0149] 502. According to the fiber core numbering sequence, the temperature-related wavelength offset data at the same axial position is added point by point to the wavelength compensation amount of the corresponding fiber core to obtain the added data;

[0150] 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 to ensure independent correction of each measurement position.

[0151] In this embodiment, the temperature-related wavelength offset data at the same axial position is first read in order of fiber core number (e.g., the offset of fiber core A at position 10m is 12pm). Then, the wavelength compensation amount for the corresponding fiber core is retrieved (+1pm for fiber core A), and the two are algebraically added together (12pm + 1pm = 13pm). Next, all fiber cores and axial positions are traversed to complete the correction calculation for the entire dataset. For example, the offset of fiber core B at position 10m, 15pm, is added to the compensation amount -0.5pm to obtain 14.5pm.

[0152] 503. Perform validity verification on the summed data to obtain a verification result. When the verification result exceeds the preset reflection wavelength range, truncate the verification result to the nearest boundary value of the range.

[0153] In step 503, validity verification refers to checking whether the corrected data meets the physical limitations of the grating reflection wavelength.

[0154] The preset reflection wavelength range refers to the effective working wavelength band of the grating defined in the etching process (e.g., 1550nm ± 2nm).

[0155] In this embodiment, the summed data is first compared with a preset reflection wavelength range. If the data exceeds the upper limit (e.g., 1552nm) or lower limit (e.g., 1548nm), the data is forcibly set to the nearest boundary value. For example, if the correction result of 1552.3pm for fiber core C at position 20m exceeds the upper limit of 1552pm, it is truncated to 1552pm. Finally, all verification results are recorded, and abnormal data points are marked.

[0156] 504 Stores the nearest boundary value as corrected wavelength data.

[0157] 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.

[0158] In this embodiment, the verified data is first categorized and stored according to the fiber core number and axial position. Then, a timestamp and position label are added to each data point. Finally, the dataset is encapsulated into a standardized output format. For example, the corrected wavelength data of 13 pm for fiber core A at position 10 m is stored as {fiber core: A; position: 10 m; wavelength offset: 13 pm}.

[0159] Here is a specific example:

[0160] In natural gas pipeline monitoring, the temperature-related wavelength offsets measured at a location of 50m for cores A / B / C of a three-core optical fiber were 18pm, 22pm, and 25pm, respectively, corresponding to stress correction factors of -0.3, +0.15, and +0.15. Through scaling (scale factor 10pm / unit coefficient), the compensation amounts were +3pm, -1.5pm, and -1.5pm, respectively. Adding these values ​​point by point yielded 21pm, 20.5pm, and 23.5pm. Verification revealed that the 21pm value for core A exceeded the preset range of 1550±2nm (i.e., 1548-1552pm), and was therefore truncated to 1552pm. The final stored data was: core A: 1552pm, core B: 20.5pm, core C: 23.5pm, generating a temperature distribution map at 50m along the pipeline.

[0161] 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 standardized data storage format provides reliable input for subsequent analysis, significantly improving the credibility and practicality of temperature detection results under complex working conditions.

[0162] To address the issues of cross-sensitivity error and insufficient data integration in multi-core fiber temperature detection, some embodiments involve interference between the composite optical signal and a reference optical signal of a preset fixed wavelength in an interferometer. The optical path difference of the interferometer is configured to generate interference fringes between each wavelength component of the composite optical signal and the reference optical signal, including:

[0163] 601. The composite optical signal and the reference optical signal are respectively fed into the beam splitting element of the interferometer, and the beam splitting element guides the two optical signals into the first optical path and the second optical path respectively;

[0164] In step 601, the beam splitter refers to an optical device (such as a fiber optic beam splitter or prism) that distributes the input optical signal proportionally to different optical paths.

[0165] The first optical path and the second optical path refer to two independent transmission paths in the interferometer, used to generate optical path difference.

[0166] In this embodiment, the composite optical signal (containing 1550 / 1555 / 1560nm components of fiber cores A / B / C) and the reference optical signal (1549nm) are first input into a beam splitter. This beam splitter then directs the two signals into the first optical path (measuring 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 that the intensity of the two optical paths is balanced.

[0167] 602. Adjust the optical path length of the first optical path so that the difference between the optical path length 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, and generate the output optical signals of the first optical path and the second optical path;

[0168] In step 602, the optical path length difference refers to the difference in the optical transmission paths of the two optical paths, which determines the characteristics of the interference fringes.

[0169] The maximum permissible difference corresponding to time stability refers to the critical value determined by the coherence length of the light source, ensuring that the interference fringes are resolvable.

[0170] In this embodiment, the 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 (e.g., 1550nm) in the composite optical signal and the reference optical signal (1549nm) in the second optical path exceeds their coherence length (e.g., the coherence length of the 1550nm light source is 20mm, and the optical path difference is set to 25mm). Next, an optical power meter is used to monitor the light intensity balance between the two signals to ensure maximum contrast of the interference fringes. For example, after adjustment, the optical path difference of the 1550nm signal from fiber core A is 25mm, while the optical path difference of the 1555nm signal from fiber core B is 25.05mm, forming a separable fringe pattern.

[0171] 603. The output optical signals are superimposed by an optical signal synthesizing element to form spatially distributed interference fringes.

[0172] In step 603, the optical signal combining element refers to a device that enables the superposition of two optical signals (such as an optical fiber coupler or a free space beam combiner).

[0173] Spatial interference fringes refer to the alternating distribution of light intensity caused by optical path difference.

[0174] In this embodiment, the output signals of the first and second optical paths are first superimposed using an optical fiber coupler. Then, the synthesized light is projected onto the imaging plane via a collimator, forming spatially distributed interference fringes. For example, the 1550nm signal from fiber core A is superimposed with the 1549nm reference light signal, forming 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 spatial separation of the fringes for each wavelength component facilitates independent subsequent analysis.

[0175] Here is a specific example:

[0176] In oil pipeline temperature monitoring, the composite optical signal (1550 / 1555 / 1560nm) from a three-core optical fiber and the reference light (1549nm) are split into two optical paths by a beam splitter. The length of the first optical path is adjusted so that the optical path difference of the 1550nm component reaches 25mm (exceeding its 20mm coherence length), and the three wavelength components interfere with the reference light respectively. After being combined by an optical fiber coupler, a CCD captures three sets of stripes with varying spacing (10μm / 10.2μm / 10.4μm), corresponding to the temperature signals of the three fiber cores.

[0177] In summary, steps 601 to 603 achieve spatial separation of multi-wavelength interference fringes through precise optical path difference control, avoiding signal crosstalk; the coordinated design of the beam splitting and combining elements ensures high fringe contrast; the spatially distributed fringes provide clear input for subsequent phase analysis, significantly improving the resolution and anti-interference capability of multi-core fiber temperature detection.

[0178] To address the issue of insufficient matching between material properties and measurement accuracy in multi-core fiber temperature detection, in some embodiments, step 303 involves temperature-related correction of the initial wavelength offset based on parameters of the physical properties of the grating structure, including:

[0179] 701. Multiply the initial wavelength offset by the temperature sensitivity coefficient of the grating structure material to obtain the multiplication result, wherein the temperature sensitivity coefficient is obtained through experimental calibration and represents the wavelength offset caused by a unit temperature change.

[0180] 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.

[0181] The result of the multiplication operation refers to the intermediate data after the initial wavelength offset has been converted by temperature characteristics.

[0182] In this embodiment, the temperature sensitivity coefficient corresponding to the current grating structure (e.g., 10 pm / ℃ for a quartz fiber grating) is first retrieved from the database. Then, the initial wavelength offset (e.g., the detected 15 pm) is multiplied by this coefficient (15 pm ÷ 10 pm / ℃ = 1.5℃) to obtain the temperature change. For example, if the initial wavelength offset of fiber core A at position 20m is 18 pm, combined with its temperature sensitivity coefficient of 9 pm / ℃, a temperature change of 2℃ is calculated.

[0183] 702. Based on the preset reflection wavelength range of the grating structure in the etching process, the multiplication result is verified to obtain the range verification result;

[0184] In step 702, the reflection wavelength range refers to the preset effective working wavelength range during grating etching (e.g., 1550nm ± 2nm).

[0185] Range verification results refer to the verification criteria for judging whether temperature correction data is within a reasonable physical range.

[0186] In this embodiment, the reflection wavelength range parameter of the grating array (e.g., 1548-1552nm) is first read, and then the result of the multiplication operation (e.g., the wavelength offset of 15pm corresponding to 1.5℃) is compared with the allowable range. For example, when the reference wavelength is 1550nm, the effective offset range is ±2nm, and it is verified whether 15pm (i.e., 0.015nm) is within this range.

[0187] 703. When the result of the multiplication operation exceeds the range verification result, the boundary value of the range is used to replace the result of the multiplication operation, and replacement processing data is generated;

[0188] In step 703, boundary value substitution refers to forcibly correcting the data to the system's allowed limit value when the data exceeds the physically reasonable range.

[0189] The data to be replaced refers to the effective wavelength offset after range constraints.

[0190] In this embodiment, abnormal data points that exceed the range are first marked (e.g., a value of 1552.3 pm is calculated at a certain location), and then the data is replaced with the nearest boundary value (1552 nm). For example, if the correction result of fiber core B at position 30 m is 1547.8 pm, which exceeds the lower limit of 1548 nm, then it is replaced with 1548 nm and the correction mark is recorded.

[0191] 704. Record the data from the replacement process as the temperature-corrected wavelength offset.

[0192] In step 704, the temperature-corrected wavelength offset refers to the final effective measurement result that conforms to physical laws and is directly related to the actual temperature change.

[0193] In this embodiment, firstly, a location label and a correction status identifier are added to each data point. Secondly, the valid data are classified and stored according to the fiber core number. For example, the corrected data sequence [12pm, 13pm, 15pm...] of fiber core A at positions 10-50m is stored as the basic temperature distribution data, and abnormal correction points are recorded separately for subsequent analysis.

[0194] Here is a specific example:

[0195] In high-voltage cable joint monitoring, fiber core A measured an initial wavelength offset of 25 pm at a hot spot location (15m). Using its temperature sensitivity coefficient of 10 pm / ℃, a temperature rise of 2.5℃ was calculated, corresponding to a wavelength offset of 25 pm within the preset range of 1550 ± 2 nm, and was directly stored as valid data. However, fiber core B, at the same location, showed an offset of 1552.3 pm due to stress interference, exceeding the upper limit of 1552 nm. The system automatically replaced this with 1552 pm and triggered an alarm signal, indicating a possible abnormal temperature rise or mechanical damage at that point.

[0196] In summary, steps 701 to 704, through the dual constraints of material property parameters and physical range, ensure that the temperature demodulation results conform to the physical laws of grating sensing; the dynamic boundary correction mechanism effectively filters out abnormal data; and the standardized data storage format provides reliable input for temperature field reconstruction, significantly improving the physical rationality and engineering applicability of the measurement results.

[0197] Figure 2 This application provides a schematic diagram of a multi-point distributed temperature detection system based on a multi-core optical fiber structure, as shown in the embodiment of the present application. Figure 2 As shown, the system includes:

[0198] The grating etching module 21 is used for fiber core structure based on multi-core optical fiber to perform grating array etching on at least three fiber cores to obtain the reflection wavelength range;

[0199] The signal reflection module 22 is used to generate reflected light signals of different bands by having the grating structure of each fiber core reflect light signals of the corresponding wavelength according to the reflection wavelength range when an external light source is incident on the multi-core optical fiber.

[0200] 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. At the same time, it uses time separation technology to perform time separation on the reflected light signals corresponding to multiple grating structures in the same fiber core to generate discrete reflection signals with discrete time distribution.

[0201] The interference processing module 24 is used to merge the independent channel signal and the discrete reflection signal, and then perform interference comparison processing with the reference light signal with a preset fixed wavelength to generate a phase difference interference signal that reflects the wavelength offset. Based on the linear relationship between the phase difference interference signal and the temperature change corresponding to the physical characteristics of the grating structure, wavelength offset analysis is performed to obtain the temperature-related wavelength offset data of each grating structure.

[0202] Error correction module 25 is used to perform multi-core joint analysis on the differences in the temperature-related wavelength offset data, and to perform bending stress error elimination processing in combination with the constraint relationship that the fiber core position is fixed during the torsional deformation of the multi-core optical fiber, so as to generate temperature detection results that are independently distributed along the axis of each fiber core.

[0203] Figure 2 The aforementioned multi-core fiber optic structure-based multi-point distributed temperature detection system can perform... 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 repeated here. The specific operation methods of each module and unit in the multi-point distributed temperature detection system based on a multi-core optical fiber structure in the above embodiments have been described in detail in the embodiments related to this method, and will not be elaborated upon here.

[0204] In one possible design, Figure 2 The illustrated embodiment of a multi-core fiber optic structure-based multi-point distributed temperature detection system 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;

[0205] The storage component 31 stores one or more computer instructions, wherein the one or more computer instructions are invoked and executed by the processing component 32.

[0206] The processing component 32 is used for the above Figure 1 The embodiment describes a multi-point distributed temperature detection method based on a multi-core optical fiber structure.

[0207] 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-described method. Alternatively, the processing component may 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-described method.

[0208] 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 storage 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 storage, flash memory, magnetic disk, or optical disk.

[0209] Of course, computing devices may also include other components, such as input / output interfaces, display components, communication components, etc.

[0210] Input / output interfaces provide interfaces between processing components and peripheral interface modules, which can be output devices, input devices, etc.

[0211] The communication components are configured to facilitate wired or wireless communication between computing devices and other devices.

[0212] The computing device can be a physical device or an elastic computing host provided by a cloud computing platform. In this case, the computing device can refer to a cloud server, and the aforementioned processing components, storage components, etc., can be basic server resources rented or purchased from the cloud computing platform.

[0213] This application also provides a computer storage medium storing a computer program, which, when executed by a computer, can perform the above-described functions. Figure 1 The embodiment shown is a multi-point distributed temperature detection method based on a multi-core optical fiber structure.

[0214] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0215] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0216] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part 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, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0217] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A multi-point distributed temperature sensing method based on a multi-core fiber structure, characterized in that, The application relates to a multi-core fiber temperature detection method and device. The multi-core fiber includes a multi-core fiber core structure, at least three fiber cores are subjected to grating array etching processing, and a reflection wavelength interval is obtained; When an external light source is incident on the multi-core fiber, the grating structure of each fiber core reflects light signals of corresponding wavelengths according to the reflection wavelength interval, and generates reflected light signals of different wavebands; A wavelength branching device is used to divide channels of the reflected light signals of different wavebands, independent channel signals corresponding to each fiber core are generated, and a time sequence separation technology is used to separate reflected light signals corresponding to multiple grating structures in the same fiber core in time sequence, and discrete reflected signals with discrete time sequence distribution are generated; After the independent channel signals and the discrete reflected signals are combined, a phase difference interference signal reflecting a wavelength shift amount is generated by interference comparison processing of the independent channel signals and the discrete reflected signals with a preset fixed wavelength reference light signal, and wavelength shift data of each grating structure related to temperature is obtained by analyzing the wavelength shift according to a linear relationship between the phase difference interference signal and temperature variation of the physical characteristics of the grating structure; The difference of the temperature-related wavelength shift data is analyzed in combination with the multi-core fiber, and a bending stress error elimination process is performed on the constraint relationship that the fiber core position is fixed when the multi-core fiber is twisted and deformed, and temperature detection results of each fiber core axially independently distributed are generated.

2. The method of claim 1, wherein, After the independent channel signals and the discrete reflected signals are combined, a phase difference interference signal reflecting a wavelength shift amount is generated by interference comparison processing of the independent channel signals and the discrete reflected signals with a preset fixed wavelength reference light signal, and wavelength shift data of each grating structure related to temperature is obtained by analyzing the wavelength shift according to a linear relationship between the phase difference interference signal and temperature variation of the physical characteristics of the grating structure. The independent channel signals from different fiber cores and the discrete reflected signals separated in time sequence in the same fiber core are subjected to optical power superposition through an optical signal combining device to form a composite optical signal; The composite optical signal and the preset fixed wavelength reference light signal interfere in an interference device, wherein the optical path difference of the interference device is set to make each wavelength component in the composite optical signal interfere with the reference light signal to generate interference fringes; The interference fringes are spatially sampled to obtain an optical intensity signal containing a phase distribution; According to the intensity variation of adjacent sampling points in the optical intensity signal, the phase difference variation of each wavelength component is calculated; The phase difference variation is mapped and associated with the reflection wavelength interval to determine the phase difference interference signal reflecting the wavelength shift amount.

3. The method of claim 2, wherein, According to the linear relationship between the phase difference interference signal and the temperature variation of the physical characteristics of the grating structure, wavelength shift data of each grating structure related to temperature is obtained, including: According to the preset reflection wavelength range of the grating structure during etching processing, a corresponding relationship data set of the phase difference variation and the wavelength shift amount is established; The phase difference variation of different wavelength components in the phase difference interference signal is matched with the corresponding relationship data set to determine the initial wavelength shift amount of each wavelength component; Based on the parameters of the physical characteristics of the grating structure, the initial wavelength shift amount is temperature-associatedly corrected, wherein the parameters of the physical characteristics include a synthetic proportion coefficient of a thermo-optic effect coefficient of a grating structure material. The temperature-affected wavelength shift of the grating structure is calculated by a multiplication relationship between the synthesis proportionality coefficient and the phase difference change amount; The temperature-affected wavelength shifts of a plurality of grating structures in the same fiber core are axially distributed and integrated to generate temperature-related wavelength shift data.

4. The method of claim 1, wherein, The differences in the temperature-related wavelength shift data are jointly analyzed for the multiple fiber cores, and a bending stress error elimination process is performed in combination with a constraint relationship that the fiber core positions are fixed when the multicore optical fiber is twisted and deformed, to generate temperature detection results that are independently distributed axially for each fiber core, including: The temperature-related wavelength shift data of different fiber cores at the same axial position are compared and analyzed, and wavelength shift difference data sets between the fiber cores are constructed; Based on a geometric constraint relationship that the relative positions of the fiber cores are fixed when the multicore optical fiber is twisted and deformed, a mapping rule between the wavelength shift difference data sets between the fiber cores and the stress distribution is established; According to the corresponding relationship between the geometric position relationship between the fiber cores and the stress distribution gradient in the mapping rule, the wavelength shift differences of the fiber cores are proportionally analyzed, and stress influence correction coefficients of the fiber cores are calculated; The stress influence correction coefficients and the temperature-related wavelength shift data of the corresponding fiber cores are superimposed to eliminate the coupling interference of the deformation stress on the wavelength shift, and corrected wavelength data are generated; The corrected wavelength data are independently arranged and combined according to the axial positions to generate temperature detection results that are independently distributed axially for each fiber core.

5. The method of claim 4, wherein, The stress influence correction coefficients and the temperature-related wavelength shift data of the corresponding fiber cores are superimposed to eliminate the coupling interference of the deformation stress on the wavelength shift, and corrected wavelength data are generated, including: The stress influence correction coefficients are converted into wavelength compensation amounts through a preset proportionality conversion relationship, wherein the numerical value of the wavelength compensation amount is proportional to the absolute value of the correction coefficient, and the sign is opposite to the sign of the stress influence correction coefficient; The temperature-related wavelength shift data at the same axial position and the wavelength compensation amounts of the corresponding fiber cores are added point by point in the order of the fiber core numbers to obtain added data; The validity of the added data is verified to obtain a verification result, and when the verification result exceeds a preset reflection wavelength range, the verification result is truncated to the nearest boundary value in the range; The nearest boundary value is stored as corrected wavelength data.

6. The method as claimed in claim 2, wherein, The composite optical signal and a reference optical signal of a preset fixed wavelength interfere with each other in an interference device, wherein the optical path difference of the interference device is set to make each wavelength component in the composite optical signal interfere with the reference optical signal to generate interference fringes, including: The composite optical signal and the reference optical signal enter a beam splitting element of the interference device respectively, and the beam splitting element guides the two optical signals into a first optical path and a second optical path respectively; The optical path length of the first optical path is adjusted so that the optical path length difference between each wavelength component in the composite optical signal and the reference optical signal in the second optical path is greater than a maximum allowed difference corresponding to the time stability of the composite optical signal, to generate output optical signals of the first optical path and the second optical path; The optical path length of the first optical path is adjusted so that the optical path length difference between each wavelength component in the composite optical signal and the reference optical signal in the second optical path is greater than a maximum allowed difference corresponding to the time stability of the composite optical signal, to generate output optical signals of the first optical path and the second optical path; The output light signals are superimposed by a light signal synthesis element to form spatially distributed interference fringes.

7. The method as claimed in claim 3, wherein, The initial wavelength offset is temperature-corrected based on a parameter of a physical property of the grating structure, including: The initial wavelength offset is multiplied by a temperature sensitivity coefficient of the grating structure material to obtain a multiplication result, wherein the temperature sensitivity coefficient is obtained by experimental calibration and represents a wavelength offset caused by a unit temperature change; The multiplication result is range-verified based on a preset reflection wavelength range of the grating structure in an etching process to obtain a range verification result; When the multiplication result exceeds the range verification result, the range boundary value is used to replace the multiplication result to generate replacement processed data; The replacement processed data is recorded as a temperature-corrected wavelength offset.

8. A multi-point distributed temperature sensing system based on a multi-core optical fiber structure, characterized by, It comprises: A grating etching module for etching at least three cores based on the core structure of a multicore optical fiber to obtain a reflection wavelength interval; A signal reflection module for reflecting light signals of corresponding wavelengths to generate reflected light signals of different wavebands when an external light source is incident on the multicore optical fiber; A signal separation module for channel dividing the reflected light signals of different wavebands using a wavelength branching device to generate independent channel signals corresponding to each core, and for time sequence separating the reflected light signals corresponding to multiple grating structures in the same core using a time sequence separation technology to generate discrete reflection signals with discrete time sequence distribution; An interference processing module for merging the independent channel signals and the discrete reflection signals, and for interference comparison processing with a reference light signal of a preset fixed wavelength to generate a phase difference interference signal reflecting a wavelength offset, and for wavelength offset analysis based on a temperature change linear relationship corresponding to the physical properties of the grating structure to obtain temperature-related wavelength offset data of each grating structure; An error correction module for multi-core joint analysis of the differences in the temperature-related wavelength offset data, and for bending stress error elimination processing in combination with the constraint relationship of fixed core positions when the multicore optical fiber is twisted and deformed to generate temperature detection results independently distributed along the axial direction of each core.

9. A computing device, comprising: It comprises 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 the multi-point distributed temperature detection method based on the multicore optical fiber structure according to any one of claims 1-7.

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

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