High-precision decoupling method for multiple parameters of long-distance optical fiber sensitive ring

Abstract

The invention provides a high-precision decoupling method for multiple parameters of a long-distance optical fiber sensitive ring, and belongs to the technical field of optical measurement and optical fiber sensing. The method is characterized by comprising the following steps: testing fast axis signals and slow axis signals of an optical fiber sensitive ring before and after temperature change by using a polarization-maintaining OFDR; calculating a cross-correlation wavelength offset and a self-correlation wavelength offset; correcting position deviation and decoupling coefficient fluctuation; decoupling to obtain temperature and thermal strain distribution in the optical fiber sensitive ring; by using the strain and temperature calibration device of the tail fiber of the optical fiber sensitive ring, the correctness of the temperature and thermal strain decoupling result of the optical fiber sensitive ring is ensured. According to the method, high-precision (+ / -0.5 DEG C, + / -5 mu epsilon) testing of internal temperature and thermal strain distribution of the kilometer-level optical fiber sensitive ring under rapid temperature change can be realized, and the method can be used for multi-parameter detection and symmetry analysis of the optical fiber sensitive ring and performance forecasting and optimization of a gyroscope system.

Description

Technical Field

[0001] This patented method belongs to the field of optical measurement and fiber optic sensing technology, and specifically involves a high-precision decoupling method for multiple parameters of a long-distance fiber optic sensitive loop. Background Art

[0002] The fiber optic sensitive ring is made of polarization-maintaining optical fiber wound in a certain way, and serves as the "brain" of fiber optic gyroscope technology to sense external posture changes. Fiber optic gyroscope technology is a guidance and control technology based on the Sagnac effect, which uses an angular velocity sensor to obtain speed, attitude and angle information. At present, fiber optic gyroscopes have basically replaced traditional mechanical gyroscopes and become the main instrument in the field of inertial measurement and guidance. Compared with mechanical gyroscopes, fiber optic gyroscopes have the advantages of high precision, low cost, anti-electromagnetic interference, long life, and small size. They have an important position and huge application value in the fields of aerospace, military, and sensing.

[0003] The fiber optic sensitive ring is a key component of the fiber optic gyroscope system, and its performance directly determines the accuracy of the fiber optic gyroscope. In the actual working process of the fiber optic gyroscope, when the internal heat and the change of ambient temperature are applied to a section of optical fiber in the fiber optic sensitive ring, temperature disturbance will be caused, and a non-reciprocal phase shift will inevitably be generated. This non-reciprocal phase shift cannot be distinguished from the phase shift caused by the rotation attitude, which will cause the fiber optic gyroscope to produce a large drift error and affect the output accuracy of the fiber optic gyroscope. In recent years, in order to improve the accuracy and dynamic range of the gyroscope to meet the needs of long-term navigation, the optical fiber used in the fiber optic sensitive ring has been gradually reduced from 125μm to 60μm, so that the winding length of the fiber optic sensitive ring is greatly increased at the same size, and the 3km-class fiber optic sensitive ring has become the mainstream of the market. Therefore, the high-precision temperature and thermal strain decoupling of long-distance fiber optic sensitive rings is of great significance to the performance evaluation of fiber optic gyroscopes.

[0004] At present, the test of optical fiber sensitive ring is mainly based on temperature change test. For example: Liu Yuanyuan, Yu Haicheng and others from Beijing Aerospace Times Optoelectronics Technology Co., Ltd. proposed a temperature test and evaluation system for optical fiber ring of optical fiber gyroscope (CN202010599862.6), which performs constant temperature test on optical fiber ring at different temperature points, and uses a large number of temperature test results to analyze the linear error based on Shupe coefficient and the nonlinear error after linear compensation to evaluate the optical fiber ring. Therefore, the simultaneous test and decoupling of temperature and thermal strain of optical fiber sensitive rings have attracted wide attention from scientific researchers. For example: Wen Kunhua, Wang Huajuan and others from Guangdong University of Technology proposed a distributed high-precision strain measurement method under temperature change conditions for optical fiber sensitive rings (CN202211009570.8), using DTS to obtain distributed temperature information of optical fiber sensitive rings and using BOTDA to obtain Brillouin frequency shift results, and then compensating stress distribution through distributed temperature information. However, this invention is limited by the spatial resolution of Brillouin distributed sensing and cannot obtain sufficiently spatially fine results.

[0005] There are also many research technologies for temperature-strain decoupling of polarization-maintaining optical fibers. For example, Lu Yuting, Zhang Naiping and others from the Central China Branch of State Grid Corporation of China and Changfei Optical Fiber and Cable Co., Ltd. proposed an optical fiber Brillouin distributed temperature and strain decoupling device and method based on ANN algorithm (CN202211709927.3). The Brillouin gain spectrum of the optical fiber to be tested is collected by integrating the data acquisition modules of OTDR and BOTDR, and input into the artificial neural network pre-trained with different temperatures and stresses, thereby decoupling the temperature and strain results. However, the invention has relatively poor effects on untrained temperature points and strain values, and the training results are only for parameter adaptation of the same type of optical fiber, and different types of optical fibers will have large errors due to different parameters. Tu Guojie, Cao Lei and others from Anhui University proposed an absolute temperature / stress measurement method based on phase OFDR (CN202410401966.X). By improving a dual-path OFDR structure, the fast-axis optical phase and the slow-axis optical phase are obtained, and the dual-axis phase is obtained by difference and spliced ​​with the fast-axis optical phase, and the absolute temperature / stress value is determined according to the temperature strain conversion coefficient. However, this invention is limited by the influence of phase noise, and there will be some splicing error points, with problems of short demodulation range and large demodulation error. Mark E. Froggatt proposed the distributed strain and temperature identification in polarization-maintaining optical fiber (US11808260). By analyzing the two scattering data of the fast axis and slow axis of the polarization-maintaining optical fiber, the temperature and strain of the optical fiber can be distinguished. However, this invention only decouples the polarization-maintaining optical fiber, and does not consider the winding stress of the winding body such as the optical fiber ring and the accuracy degradation caused by the misalignment of the optical fiber length. Xue Yuanze, Wang Xuefeng and others from the Beijing Institute of Aeronautics and Astronautics Control Devices proposed a position deviation compensation algorithm based on maximum cross-correlation (doi:10.1364 / AO.442248). By comparing the window correlation within a certain step length, the window with the strongest correlation is recorded as the compensated window, thereby compensating for the position deviation caused by temperature or strain changes in the optical fiber to be tested and the auxiliary interferometer. However, this correction scheme traverses all nearby windows, and the algorithm has high time and hardware overhead, which is not suitable for long-distance optical fiber position deviation correction. He Zuyuan and others from Shanghai Jiaotong University proposed a centimeter-level spatial resolution DTS system based on polarization-sensitive OFDR (doi:10.1109 / JLT.2021.3052036). By calculating the Rayleigh backscattering spectrum difference between the fast axis and the slow axis, the birefringence distribution along the optical fiber direction is demodulated, and the absolute temperature information is demodulated through the relationship between absolute temperature and birefringence. However, the temperature measurement uncertainty of this scheme is affected by the inhomogeneity of the birefringence of the polarization-maintaining fiber and is also limited by random noise. At the same time, it is impossible to achieve simultaneous decoupling of temperature and strain.Wenhai Li and others from the University of Ottawa proposed a polarization-sensitive optical frequency domain reflectometer to measure temperature and strain simultaneously, and calculated the temperature and strain coefficient of the polarization-maintaining fiber by autocorrelation and cross-correlation of the spectrum to form a distributed parameter matrix to compensate for the measurement error. However, this scheme did not consider the accuracy degradation in kilometer-level fiber demodulation due to the position deviation of the fiber due to temperature or strain.

[0006] In addition, there are also optical fibers, methods and equipment for precise optical fiber measurement under multiple stimuli proposed by LUNA Company of the United States (US15525306), which use the characteristics of different core changes of multi-core optical fibers to decouple temperature and strain; Mao Yan, Tong Xinglin and others from Weihai Research Institute of Wuhan University of Technology proposed a temperature strain monitoring system and method based on a differently doped dual-core weak reflection FBG array (CN202111297771.8), which uses the characteristics of different temperature / strain sensitivity coefficients of different doped cores to achieve decoupling of temperature strain. These schemes have improved and optimized the sensing optical fiber, and decoupled the temperature and strain changes based on the principle that different optical fibers have different temperature and strain changes, but these methods cannot be applied to the testing of optical fiber sensitive rings. Summary of the invention

[0007] The purpose of the present invention is to provide a high-precision decoupling method for multiple parameters of a long-distance optical fiber sensitive ring. In the temperature variation test of the optical fiber sensitive ring, the influence of the intrinsic decoupling coefficient fluctuation caused by the winding stress and the demodulation accuracy degradation caused by the optical fiber length misalignment on the measurement is eliminated, thereby achieving high-precision temperature and thermal strain decoupling of the long-distance optical fiber sensitive ring.

[0008] The invention proposes a high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop, which is characterized in that the process is divided into the following steps:

[0009] Step S1: Build a fiber optic sensitive ring test system and build a calibration fiber optic module;

[0010] Step S2: Performing a fiber sensitive ring test to obtain a reference fast axis signal, a reference slow axis signal, a test fast axis signal, and a test slow axis signal;

[0011] By correcting the position deviation, a corrected cross-correlation wavelength offset and an autocorrelation wavelength offset difference are obtained;

[0012] Step S4: obtaining the cross-correlation wavelength offset and the corrected autocorrelation wavelength offset difference by correcting the decoupling coefficient;

[0013] Step S5: Substitute the decoupling formula to obtain the actual temperature strain result, and judge the decoupling result and the calibration fiber. If the calibration fiber decoupling result meets the requirements, it proves that the demodulation result is correct, otherwise return to step S3 for re-correction.

[0014] The high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop according to claim 1 is characterized in that: the step S1 is divided into the following steps:

[0015] Select a fiber sensitive ring 201 to be tested, and fuse a certain length of extended polarization-maintaining fiber 202 to the output pigtail 201a of the fiber sensitive ring 201 to be tested, wherein the fiber sensitive ring 201 to be tested, its output pigtail 201a, and its input pigtail 201b are all polarization-maintaining fibers;

[0016] Build a strain calibration device, select a certain length of the extended polarization-maintaining optical fiber 202 as the strain calibration segment optical fiber 202a, glue it to the optical fiber strain tensile platform 22, apply a fixed strain, and place it inside the rapid temperature control test box 23;

[0017] Build a temperature calibration device, select the part of the extended polarization-maintaining optical fiber 202 that is not in the optical fiber strain test table as the temperature calibration segment optical fiber 202b, and place the temperature calibration segment optical fiber in a relaxed state inside the rapid temperature control test box 23 without applying additional stress;

[0018] Connect the test system, place the optical fiber sensitive ring 201 to be tested in the rapid temperature control test box 23, and connect the optical fiber sensitive ring 201 to be tested to the OFDR test system 21 through the input pigtail 201b.

[0019] The high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop according to claim 1 is characterized in that: step S2 is divided into the following steps:

[0020] Perform a first test, start the OFDR test system 21, obtain first distributed fast axis and slow axis signals, use the obtained first distributed fast axis signal as a reference fast axis signal, and use the obtained first distributed slow axis signal as a reference slow axis signal;

[0021] After setting the temperature excitation, start the rapid temperature control test box 23, wait for the temperature to stabilize, start the OFDR test system 21, obtain the second distributed fast axis and slow axis signals, use the obtained second distributed fast axis signal as the test fast axis signal, and use the obtained second distributed slow axis signal as the test slow axis signal;

[0022] The high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop according to claim 1 is characterized in that: the step S3 is divided into the following steps:

[0023] Step 301: Perform Fourier transform on the reference fast axis signal, the reference slow axis signal, the test fast axis signal and the test slow axis signal to obtain the reference fast axis signal scattering spectrum, the reference slow axis signal scattering spectrum, the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum;

[0024] Step 302: Divide the reference fast-axis signal scattering spectrum, the reference slow-axis signal scattering spectrum, the test fast-axis signal scattering spectrum and the test slow-axis signal scattering spectrum into N segments, where N is the ratio of the scattering spectrum data length to the adopted test spatial resolution, and each segment of the scattering spectrum of different signals is one-to-one corresponding;

[0025] Step 303: Correct the position deviation of the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum, calculate the correlation between the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum at the corresponding positions, obtain the correlation spectrum corresponding to each section of the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum, take the xth section of the correlation spectrum, and obtain the maximum position of the correlation spectrum amplitude and the position of the relevant spectrum amplitude , subtract them to get the position deviation of the test fast axis signal scattering spectrum at the xth segment relative to the reference fast axis signal scattering spectrum , and based on the position deviation of each segment , fit the test fast axis signal scattering spectrum relative to the reference fast axis signal position deviation distribution, recorded as the reference test position deviation distribution;

[0026] Step 304: performing position deviation correction on the reference fast-axis signal scattering spectrum and the reference slow-axis signal scattering spectrum according to step 303 to obtain a position deviation distribution of the reference slow-axis signal scattering spectrum relative to the reference fast-axis signal, and interpolating the reference slow-axis signal scattering spectrum according to the distribution to obtain a corrected reference slow-axis signal scattering spectrum;

[0027] Step 305: performing position deviation correction on the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum according to step 303 to obtain the position deviation distribution of the test slow axis signal scattering spectrum relative to the test fast axis signal, and interpolating the test slow axis signal scattering spectrum according to the distribution to obtain the corrected test slow axis signal scattering spectrum;

[0028] Step 306: Demodulate the reference fast axis signal and the corrected test fast axis signal to obtain the cross-correlation wavelength offset ; Correlation demodulation of the reference fast axis signal and the corrected reference slow axis signal is performed to obtain a reference autocorrelation wavelength offset; correlation demodulation of the test fast axis signal and the corrected test slow axis signal is performed to obtain a test autocorrelation wavelength offset;

[0029] Step 307: interpolating the test autocorrelation wavelength offset according to the recorded reference test position deviation distribution to obtain a corrected test autocorrelation wavelength offset;

[0030] Step 308: subtracting the corrected reference autocorrelation wavelength offset from the test autocorrelation wavelength offset to obtain an autocorrelation wavelength offset difference;

[0031] The high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop according to claim 1 is characterized in that: the step S4 is divided into the following steps:

[0032] Step 401: The reference autocorrelation wavelength offset after position deviation correction Take the derivative and add one to it as the correction form for the decoupling coefficient;

[0033] Step 402: Correct the autocorrelation wavelength offset difference using the decoupling coefficient correction formula The correction is performed to obtain the autocorrelation wavelength offset difference after the decoupling coefficient is corrected. The correction formula is as follows:

[0034]

[0035] The high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop according to claim 1 is characterized in that: the step S5 is divided into the following steps:

[0036] The autocorrelation wavelength shift difference , cross-correlation wavelength offset , step and the autocorrelation temperature coefficient of the optical fiber used in the polarization-maintaining optical fiber ring , autocorrelation strain coefficient , cross-correlation temperature coefficient , cross-correlation strain coefficient Substitute into the decoupling formula and calculate the temperature decoupling result Decoupling results of thermal strain , the decoupling formula is as follows:

[0037]

[0038] The obtained decoupling result is judged to determine whether it satisfies the requirements that the strain value obtained by the strain decoupling result at the optical fiber 202a of the strain calibration section is the same as the strain applied by the optical fiber strain tension table 22, and the temperature change obtained by the temperature decoupling result is the same as the temperature excitation set in the rapid temperature control test box 23, and whether the strain value obtained by the strain decoupling result at the optical fiber 202b of the temperature calibration section is 0, and the temperature change obtained by the temperature decoupling result is the same as the temperature excitation set in the rapid temperature control test box 23. If the decoupling result meets the requirements, it proves that the decoupling result is correct, otherwise return to step S3 for re-correction.

[0039] Compared with the prior art, the advantages of the present invention are:

[0040] 1. The present invention can achieve the decoupling of temperature and thermal strain of the optical fiber sensitive ring under rapid temperature change.

[0041] 2. The present invention extends the decoupling distance to the kilometer level by correcting the position deviation, and can realize long-distance optical fiber sensitive loop testing.

[0042] 3. The present invention improves the decoupling accuracy by correcting the decoupling coefficient, and can achieve a temperature decoupling accuracy of ±0.5°C and a strain decoupling accuracy of ±5με.

[0043] 4. The calibration device is used to ensure the correctness of the temperature and strain decoupling results. The distributed temperature and thermal strain results of the optical fiber sensitive ring can be obtained simultaneously through one scan. The test efficiency is high and the stability is good. It can be used for performance prediction, symmetry optimization, quality evaluation and screening of optical fiber sensitive rings, and the development of high-performance multi-parameter sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of a high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop.

[0045] Figure 2 This is the structure diagram of the long-distance optical fiber sensitive ring multi-parameter test device

[0046] Figure 3 This is the flow chart of position deviation correction and decoupling coefficient correction

[0047] Figure 4 This is a comparison chart of the reference slow axis signal scattering spectrum and the test slow axis signal scattering spectrum before and after position deviation correction.

[0048] Figure 5 This is the demodulation result of the cross-correlation wavelength offset

[0049] Figure 6 This is the demodulation result diagram of the reference autocorrelation wavelength offset and the test autocorrelation wavelength offset after position deviation correction.

[0050] Figure 7 This is a comparison of the autocorrelation wavelength offset difference before and after the decoupling coefficient correction.

[0051] Figure 8 The temperature and thermal strain decoupling results of the extended polarization-maintaining fiber section are shown in the figure.

[0052] Fig. 9 This is the temperature decoupling result of the optical fiber sensitive ring

[0053] Fig.10 This is the result of thermal strain decoupling of the optical fiber sensitive ring. DETAILED DESCRIPTION

[0054] In order to clearly illustrate the high-precision decoupling method of multiple parameters of a long-distance optical fiber sensitive loop of the present invention, the present invention is further described in conjunction with embodiments and drawings, but this should not limit the protection scope of the present invention.

[0055] Build as Figure 2 The optical fiber sensitive loop test device shown in the figure is a process for high-precision decoupling of multiple parameters of a long-distance optical fiber sensitive loop. Figure 1 As shown:

[0056] Select a fiber sensitive loop to be tested with a fiber length of about 3 km, and fuse the end of the output pigtail of the sensitive loop to extend the length of the polarization-maintaining fiber to 12 meters;

[0057] Select a 0.5-meter-long optical fiber as the strain calibration section optical fiber at a position 3 meters away from the fusion point of the extended polarization-maintaining optical fiber and the output pigtail of the optical fiber sensitive ring, and fix it on the optical fiber strain tensile table with a stretching length of 60 microns, i.e. 120 microstrains. Place the optical fiber strain tensile table inside a rapid temperature control test box;

[0058] The entire extended polarization-maintaining optical fiber is used as a temperature calibration section optical fiber, and the portion of the temperature calibration section optical fiber that is not in the optical fiber strain test table is placed in a relaxed state inside the rapid temperature control test box, that is, no additional stress is applied to the portion of the temperature calibration section optical fiber that is not in the optical fiber strain test table inside the rapid temperature control test box;

[0059] Place the optical fiber sensitive ring to be tested inside the rapid temperature control test box;

[0060] The OFDR test system is started, and the first distributed fast axis result obtained is recorded as the reference fast axis result, and the first distributed slow axis result obtained is recorded as the reference slow axis result;

[0061] Start the rapid temperature control test box, set the heating rate to 2 degrees Celsius per minute, heat for 1 minute and then keep warm. After the temperature stabilizes, start the OFDR test system, record the second distributed fast axis result obtained as the test fast axis result, and record the second distributed slow axis result obtained as the reference slow axis result;

[0062] The position deviation correction and the decoupling coefficient correction are performed by referring to the fast axis signal, the slow axis signal, the test fast axis signal, and the test slow axis signal. The correction process is as follows: Figure 3 As shown:

[0063] First, Fourier transform is performed on the reference fast axis signal, the reference slow axis signal, the test fast axis signal and the test slow axis signal to obtain the reference fast axis signal scattering spectrum, the reference slow axis signal scattering spectrum, the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum;

[0064] Divide the reference fast axis signal scattering spectrum, the reference slow axis signal scattering spectrum, the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum into N segments (N is the data length / test spatial resolution)

[0065] Calculate the correlation between the scattering spectrum of each section of the reference fast axis signal and the test fast axis signal, take the position corresponding to the maximum correlation value and the position corresponding to the minimum correlation, subtract the two to obtain the position deviation of the signal, and obtain the position deviation distribution between the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum through the position deviation result of each section, which is recorded as the reference test position deviation distribution;

[0066] Processing the reference fast axis signal scattering spectrum and the reference slow axis signal scattering spectrum according to the above method to obtain the position deviation distribution between the reference fast axis signal scattering spectrum and the reference slow axis signal scattering spectrum, and performing polynomial interpolation on the reference slow axis signal according to the distribution;

[0067] According to the above method, the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum are processed to obtain the position deviation distribution between the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum, and polynomial interpolation is performed on the test slow axis signal according to the distribution;

[0068] The comparison between the reference slow axis signal and the test slow axis signal before and after position correction is as follows Figure 4 As shown;

[0069] The OFDR correlation demodulation method is used to demodulate the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum to obtain the cross-correlation wavelength offset, such as Figure 5 As shown;

[0070] The reference fast-axis signal scattering spectrum and the reference slow-axis signal scattering spectrum corrected by the position deviation are demodulated by the OFDR correlation demodulation method to obtain the reference autocorrelation wavelength offset. Similarly, the test fast-axis signal scattering spectrum and the test slow-axis signal scattering spectrum corrected by the position deviation are demodulated to obtain the test autocorrelation wavelength offset. The reference autocorrelation wavelength offset and the test autocorrelation wavelength offset are corrected by the position deviation using the recorded reference test position deviation distribution to obtain the reference autocorrelation wavelength offset and the test autocorrelation wavelength offset after the position deviation correction. Figure 6 As shown;

[0071] Subtract the reference autocorrelation wavelength offset after position deviation correction from the test autocorrelation wavelength offset to obtain the autocorrelation wavelength offset difference. ;

[0072] Further take the reference autocorrelation wavelength offset , take its derivative and add 1 to it, record it as the decoupling coefficient correction form, and take the autocorrelation wavelength offset difference Substituting into the following formula, we can get the autocorrelation wavelength offset difference after the decoupling coefficient is corrected: ;

[0073]

[0074] Comparison of the autocorrelation wavelength offset difference before and after the decoupling coefficient correction is as follows: Figure 7 Shown

[0075] The autocorrelation temperature coefficient of the optical fiber used in the polarization-maintaining fiber ring will be measured , autocorrelation strain coefficient , cross-correlation temperature coefficient , cross-correlation strain coefficient and the autocorrelation wavelength shift difference and the cross-correlation wavelength shift Substitute into the decoupling formula to get the temperature decoupling result Decoupling results of thermal strain , the decoupling formula is as follows:

[0076]

[0077] Temperature decoupling results for extended PM fiber section Decoupling results of thermal strain The results of temperature and thermal strain decoupling of the extended polarization-maintaining fiber section are as follows: Figure 8 As shown in the figure, when only the strain calibration section of the optical fiber has a strain value of 120 microstrain in the thermal strain decoupling result and the temperature calibration section of the optical fiber is 2 degrees Celsius in the temperature decoupling result, the decoupling result is correct. Fig. 9 The thermal strain decoupling results are shown in Fig.10 As shown in the figure, the temperature and thermal strain decoupling of the 3km long-distance optical fiber sensitive ring is realized, with a temperature decoupling accuracy of ±0.5℃ and a strain decoupling accuracy of ±5με.

Claims

1. A high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop, characterized by: The process is divided into the following steps: 1) Step S1: Build a fiber optic sensitive ring test system and build a calibration fiber optic module; 2) Step S2: Performing a fiber sensitive ring test to obtain a reference fast axis signal, a reference slow axis signal, a test fast axis signal, and a test slow axis signal; 3) Step S3: obtaining a corrected cross-correlation wavelength offset and an autocorrelation wavelength offset difference by position deviation correction; 4) Step S4: by correcting the decoupling coefficient, the cross-correlation wavelength offset and the corrected autocorrelation wavelength offset difference are obtained; 5) Step S5: Substitute the decoupling formula to obtain the actual temperature strain result, and judge the decoupling result and the calibration fiber. If the decoupling result of the calibration fiber meets the requirements, it proves that the demodulation result is correct, otherwise return to step S3 for re-correction.

2. A high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop as claimed in claim 1, characterized in that: The step S1 is divided into the following steps: 1) selecting a fiber optic sensitive ring (201) to be tested, and fusing a certain length of extended polarization-maintaining fiber (202) to the output pigtail (201a) of the fiber optic sensitive ring (201) to be tested, wherein the fiber optic sensitive ring (201) to be tested, its output pigtail (201a) and its input pigtail (201b) are all polarization-maintaining fibers; 2) constructing a strain calibration device, selecting a certain length of the extended polarization-maintaining optical fiber (202) as a strain calibration segment optical fiber (202a), bonding it to an optical fiber strain tensile platform (22), applying a fixed strain, and placing it inside a rapid temperature control test box (23); 3) constructing a temperature calibration device, selecting a portion of the extended polarization-maintaining optical fiber (202) that is not in the optical fiber strain test bench as a temperature calibration segment optical fiber (202b), and placing the temperature calibration segment optical fiber in a relaxed state inside a rapid temperature control test box (23) without applying additional stress; 4) Connecting the test system, placing the optical fiber sensitive ring (201) to be tested in a rapid temperature control test box (23), and connecting the optical fiber sensitive ring (201) to be tested to the pigtail (201b) of the OFDR test system (21).

3. A high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop as claimed in claim 1, characterized in that: The step S2 is divided into the following steps: 1) Performing the first test, starting the OFDR test system (21), obtaining the first distributed fast axis and slow axis signals, using the obtained first distributed fast axis signal as a reference fast axis signal, and using the obtained first distributed slow axis signal as a reference slow axis signal; 2) After setting the temperature excitation, start the rapid temperature control test box (23), wait for the temperature to stabilize, start the OFDR test system (21), obtain the second distributed fast axis and slow axis signals, use the obtained second distributed fast axis signal as the test fast axis signal, and use the obtained second distributed slow axis signal as the test slow axis signal.

4. A high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop as claimed in claim 1, characterized in that: The step S3 is divided into the following steps: 1) Step (301): performing Fourier transform on the reference fast axis signal, the reference slow axis signal, the test fast axis signal and the test slow axis signal to obtain a reference fast axis signal scattering spectrum, a reference slow axis signal scattering spectrum, a test fast axis signal scattering spectrum and a test slow axis signal scattering spectrum; 2) Step (302): Divide the reference fast-axis signal scattering spectrum, the reference slow-axis signal scattering spectrum, the test fast-axis signal scattering spectrum, and the test slow-axis signal scattering spectrum into N segments, where N is the ratio of the scattering spectrum data length to the test spatial resolution used, and each segment of the scattering spectrum of different signals is in one-to-one correspondence; 3) Step (303): Correct the position deviation of the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum, calculate the correlation between the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum at the corresponding positions, obtain the correlation spectrum corresponding to each section of the reference fast axis signal scattering spectrum and the test fast axis signal scattering spectrum, take the xth section of the correlation spectrum, and obtain the maximum position of the correlation spectrum amplitude and the position of the relevant spectrum amplitude , subtract them to get the position deviation of the test fast axis signal scattering spectrum at the xth segment relative to the reference fast axis signal scattering spectrum , and based on the position deviation of each segment , fit the test fast axis signal scattering spectrum relative to the reference fast axis signal position deviation distribution, recorded as the reference test position deviation distribution; 4) Step (304): performing position deviation correction on the reference fast axis signal scattering spectrum and the reference slow axis signal scattering spectrum according to step (303) to obtain a position deviation distribution of the reference slow axis signal scattering spectrum relative to the reference fast axis signal, and interpolating the reference slow axis signal scattering spectrum according to the distribution to obtain a corrected reference slow axis signal scattering spectrum; 5) Step (305): performing position deviation correction on the test fast axis signal scattering spectrum and the test slow axis signal scattering spectrum according to step (303) to obtain a position deviation distribution of the test slow axis signal scattering spectrum relative to the test fast axis signal, and interpolating the test slow axis signal scattering spectrum according to the distribution to obtain a corrected test slow axis signal scattering spectrum; 6) Step (306): performing correlation demodulation on the reference fast axis signal and the corrected test fast axis signal to obtain a cross-correlation wavelength offset; The reference fast axis signal and the corrected reference slow axis signal are correlated and demodulated to obtain a reference autocorrelation wavelength offset; The test fast axis signal and the corrected test slow axis signal are demodulated to obtain the test autocorrelation wavelength offset; 7) Step (307): interpolating the test autocorrelation wavelength offset according to the recorded reference test position deviation distribution to obtain a corrected test autocorrelation wavelength offset; 8) Subtract the corrected reference autocorrelation wavelength offset from the test autocorrelation wavelength offset to obtain the autocorrelation wavelength offset difference.

5. A high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop as claimed in claim 1, characterized in that: The step S4 is divided into the following steps: 1) Step (401): The reference autocorrelation wavelength offset after position deviation correction is Take the derivative and add one to it as the correction form for the decoupling coefficient; 2) Step (402): Correct the autocorrelation wavelength offset difference using the decoupling coefficient Correction is performed to obtain the autocorrelation wavelength offset difference after the decoupling coefficient is corrected , the correction formula is as follows:

6. A high-precision decoupling method for multi-parameters of a long-distance optical fiber sensitive loop as claimed in claim 1, characterized in that: The step S5 is divided into the following steps: 1) The autocorrelation wavelength offset difference , cross-correlation wavelength offset , step and the autocorrelation temperature coefficient of the optical fiber used in the polarization-maintaining optical fiber ring , autocorrelation strain coefficient , cross-correlation temperature coefficient , cross-correlation strain coefficient Substitute into the decoupling formula and calculate the temperature decoupling result Decoupling results of thermal strain , the decoupling formula is as follows: 2) judging the obtained decoupling result to determine whether the strain value obtained by the strain decoupling result at the strain calibration section optical fiber (202a) is the same as the strain applied by the optical fiber strain tension table (22), and the temperature change obtained by the temperature decoupling result is the same as the temperature excitation set in the rapid temperature control test box (23), and whether the strain value obtained by the strain decoupling result at the temperature calibration section optical fiber (202b) is 0, and the temperature change obtained by the temperature decoupling result is the same as the temperature excitation set in the rapid temperature control test box (23). If the decoupling result meets the requirements, it is proved that the decoupling result is correct; otherwise, return to step S3 for re-correction.

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