Method for measuring physical symmetry of optical fiber sensitive ring in temperature field

Abstract

The invention provides a physical symmetry measurement method for an optical fiber sensitive ring, and belongs to the technical field of optical measurement and optical fiber sensing. The method comprises the following steps of: measuring temperature variation and thermal strain of an optical fiber ring at different temperatures by adopting a polarization-maintaining OFDR (Optical Frequency Domain Reflectometer) and a multi-parameter decoupling technology; calculating asymmetric refractive index distribution under temperature change, and then calculating a correlation coefficient of a layer / turn unit to evaluate the physical symmetry of a unit; and accumulating the correlation coefficient sum of the whole unit to obtain an equivalent correlation coefficient, and calculating the full-temperature equivalent correlation coefficient distribution of all temperature points so as to realize the evaluation of the physical symmetry. According to the method, quantitative physical symmetry evaluation can be realized, the physical symmetry between layers and turns of the optical fiber can be deeply evaluated in combination with data with high spatial resolution, the physical symmetry fault of the optical fiber ring is diagnosed, and the method plays an important role in winding process optimization, quality evaluation and yield improvement of the optical fiber ring.

Description

Technical Field

[0001] This patented method belongs to the field of fiber optic gyroscope testing, and specifically involves a method for testing the physical symmetry of a fiber optic sensitive ring under a temperature field based on optical frequency domain reflection. Background Art

[0002] The fiber optic gyroscope is a high-precision angular velocity measuring instrument based on the Sagnac effect invented in the 1970s. However, the sensitive ring in the fiber optic gyroscope is easily affected by the environment. For example, changes in the external temperature environment will directly cause the zero position drift of the fiber optic gyroscope, which seriously restricts the improvement of the gyroscope performance.

[0003] Physical symmetry is also called optical symmetry or optical path symmetry, which refers to the consistency between the midpoint of the optical path of the gyro sensitive ring and the midpoint of the actual length of the optical fiber. It directly affects the performance of the Mohr effect and Shupe effect of the gyro. The factors affecting physical symmetry mainly come from the differences in material properties of the components inside the optical fiber ring and the asymmetry of their temperature response. Compared with geometric symmetry, physical symmetry is the direct cause of thermally induced zero drift of the fiber optic gyroscope.

[0004] Optical frequency domain reflection technology was first proposed by Eickhoff in 1981. Since then, it has been widely studied and improved due to the advantages of optical frequency domain reflection system such as high spatial resolution and dynamic range. However, due to the mutual restriction between test length and sensing accuracy, it is impossible to achieve the overall gyroscope optical path test over a long distance. For example, Yu Ting, Yan Zhibing and others from Huaxing Xinrui Communication Technology Group Co., Ltd. announced a method for positioning and detecting the center point of the optical path of a thin fiber ring (CN106706001A). This method uses the technology of engraving fiber gratings with femtosecond lasers to engrave fiber gratings near the approximate center point of the sensitive ring. Then, relying on optical frequency domain reflection technology, the center point of the optical path of the polarization-maintaining fiber sensitive ring is accurately located by accurately detecting the position of the fiber grating in the polarization-maintaining fiber sensitive ring. However, its use requires the midpoint of the total length of the optical fiber to be estimated in advance before winding it into a ring. It is impossible to directly perform physical symmetry tests on the gyroscope optical path, nor can it detect other defects inside the fiber sensitive ring.

[0005] In 2008, Yao Xiaotian and others from Beijing Gaoguang Technology Co., Ltd. announced a method and device for measuring the quality of fiber rings for fiber optic gyroscopes (CN101339093B). By applying radial and axial temperature excitations to the fiber rings and combining the simulation results of the three-dimensional mathematical model of the fiber rings, the quantified radial and axial equivalent asymmetry information of the fiber ring winding was obtained. However, due to the limitations of the test parameters such as the spatial resolution and strain accuracy of the test instrument, it is currently impossible to achieve high-precision measurement of the full-temperature physical symmetry of the fiber sensitive ring under the temperature field. The low test accuracy and the failure to correct the test parameters in combination with information such as polarization crosstalk of the fiber sensitive ring also lead to large errors in the final test results.

[0006] In 2012, Suzhou Guanghuan Technology Co., Ltd. disclosed a method and device for detecting the quality of optical fiber rings for gyroscopes (CN103048115B). The radial temperature excitation is applied to the optical fiber ring to be tested, and the equivalent asymmetric length of the optical fiber ring to be tested is determined by measurement, thereby determining the quality of the optical fiber ring. Due to the limitations of its test instrument and test method, it is impossible to achieve the distributed characteristic parameter accuracy measured by a high-precision OFDR test system. At the same time, this method is also unable to quantitatively analyze the main influencing factor of the gyroscope zero drift, that is, the physical symmetry of the optical fiber sensitive ring.

[0007] In 2014, Yang Dongkun and others from the 618th Institute of China Aviation Industry proposed a method for evaluating and compensating the reciprocal symmetry of an optical fiber ring (CN104296964B). The invention uses enhanced Brillouin backreflection detection technology to obtain the internal stress state distribution data of the optical fiber ring that characterizes the reciprocal symmetry. The distribution data is used to establish a symmetry model within the working temperature range and analyze and evaluate the reciprocal symmetry of the optical fiber ring to be tested; according to the optimal reciprocal symmetry position and the error size and error direction, the relationship between the actual geometric symmetry position and the optical symmetry position is adjusted to compensate for the error. However, this invention is limited by the spatial resolution and strain accuracy of the Brillouin backreflection detection technology and cannot perform high-precision detection of the strain inside the optical fiber ring, and its stress state distribution data has large errors.

[0008] Beijing Zhongke Panhua Measurement & Control Technology Co., Ltd. proposed a fiber optic gyroscope test system and test method (CN117191078A). This method places several fiber optic gyroscope groups on a test turntable in an incubator. The incubator adjusts the temperature according to a preset temperature curve, and the test turntable adjusts the speed according to a preset speed to drive the fiber optic gyroscope group to rotate. The output voltage value corresponding to the fiber optic gyroscope is obtained through a data acquisition board. The predicted output voltage value of the gyroscope system output voltage is compared with the actual output voltage value to obtain the judgment result of the fiber optic gyroscope group. It is used to test the performance parameters of the fiber optic gyroscope at a temperature of -55°C to 80°C during dynamic and static periods. This test method can only perform qualification screening on the entire gyroscope system and cannot test internal parameters such as the symmetry of the fiber optic sensitive ring.

[0009] In 2019, the 707th Institute of China Shipbuilding Industry Corporation disclosed a fiber optic gyroscope ring assembly scale stability test and analysis method (CN109357690A). This method divides the fiber optic gyroscope into a ring assembly module (including the ring and Y-waveguide) and an optoelectronic module (including light source and circuit), and eliminates the influencing factors of the fiber optic gyroscope other than the ring assembly to the greatest extent to test the stability of the gyroscope system scale factors. However, it is not suitable for quantitative measurement of the physical symmetry of the gyroscope optical path under temperature field.

[0010] In 2017, the Tianjin Navigation Instrument Research Institute published a paper (THE EXPRESS TEST OF WINDING SYMMETRYQUALITY IN FOG FIBER COILS) that experimentally studied the symmetry characteristics of the fiber optic gyroscope ring under periodic temperature excitation, and introduced the equivalent asymmetry (EAD) to quantify the winding symmetry quality of the fiber optic coil. A fast EAD measurement method was proposed, which can quickly detect the winding symmetry quality of the fiber optic gyroscope ring. However, the paper did not analyze and explain in detail the physical symmetry of the gyroscope optical path under the temperature field, nor did it distinguish the effects of physical symmetry and geometric symmetry on the gyroscope zero drift performance.

[0011] In 2021, Beijing Aerospace Times Optoelectronics Technology Co., Ltd. published a paper (Optical Fiber Ring Temperature Performance Evaluation Method Based on Equivalent Asymmetric Length). According to the Shupe error mechanism, it can be known that only when the equivalent midpoint coincides with the physical midpoint can the zero bias error caused by temperature on both sides of the equivalent midpoint be completely opposite. This paper proposes an optical fiber ring evaluation method based on equivalent asymmetric length, and quantitatively evaluates the symmetry of the optical fiber ring through the equivalent asymmetric length of the optical fiber ring.

[0012] In 2023, the 16th Institute of China Aerospace Science and Technology Corporation published a paper on precision winding technology, which found that the symmetry of the fiber optic ring affects the temperature performance of the fiber optic gyroscope. Fiber optic rings with good symmetry also have good temperature performance. The OFDR-based fiber optic ring optical center detection method used in this paper can effectively detect the optical asymmetry of the fiber optic ring relative to the center point, but does not detect the physical asymmetry of the gyroscope optical path as a whole.

[0013] The above evaluation and testing methods are helpful for the symmetry screening of optical fiber rings under temperature field, but have no guiding significance for the application and improvement of optical fiber gyroscopes. The symmetry of optical fiber sensitive rings under temperature field is a manifestation of the comprehensive performance of optical fiber gyroscopes. This parameter is affected by many factors such as the winding method of optical fiber sensitive rings, the optical fiber winding state, and the strain distribution of the overall gyroscope optical path. It is not only a key factor in determining the temperature performance of optical fiber gyroscopes, but the method described in the present invention can accurately evaluate the physical symmetry of the gyroscope optical path under temperature field, and at the same time has a direct and effective guiding role in the improvement and adjustment of the gyroscope optical path. Summary of the invention

[0014] A method for measuring the physical symmetry of an optical fiber sensitive ring under a temperature field. The method first requires the construction of a high-performance OFDR test system to test the distributed characteristic parameter (temperature and strain) data of the optical fiber sensitive ring, and calculate the refractive index variable of the winding body based on the data, and then perform layer turn symmetry analysis. The method for measuring the symmetry of an optical fiber sensitive ring under a temperature field is characterized in that the method comprises the following steps:

[0015] Step 1 101: first, the temperature field for the optical fiber sensitive ring test needs to be configured so that it meets the temperature field test conditions described in the method of the present invention;

[0016] Step 2 102: Use a high-performance optical frequency domain reflectometry system to measure distributed characteristic parameters of the optical fiber sensitive ring in the temperature field;

[0017] Step 3 103: According to the test requirements, several representative specific temperature points in the temperature field are selected for subsequent testing;

[0018] Step 4 104: performing multi-parameter simultaneous decoupling processing on the temperature and strain parameters in the distributed characteristic parameters obtained by the high-performance optical frequency domain reflectometry system test;

[0019] Step five 105: Demodulating the distributed characteristic parameters to obtain the temperature variation of the optical fiber sensitive ring in the applied temperature field;

[0020] Step 6 106: Demodulating the parameters obtained by the high-performance OFDR test can obtain the thermal strain generated by the optical fiber sensitive ring under the temperature field;

[0021] Step 7 107: Calculate the asymmetric refractive index of the winding body under the action of thermal strain by using the distributed temperature and strain characteristic parameter data of the optical fiber sensitive ring obtained by multi-parameter decoupling. First, calculate the change in refractive index under thermal strain The calculation formula is:

[0022]

[0023] in, is the standard refractive index, and is the photoelastic coefficient, is the axial thermal strain, is the thermo-optical coefficient of the optical fiber; the clockwise (CW) incident light in the optical fiber sensitive ring is disturbed by the external temperature at point s in the optical fiber sensitive ring, resulting in a refractive index change, which leads to a positive phase difference; similarly, the counterclockwise (CCW) incident light will also have a refractive index change at Ls, but a negative phase difference will be generated. Therefore, different refractive index changes are generated on the symmetrical length. By making a difference, we get an asymmetric distribution of the refractive index. The asymmetric refractive index distribution The calculation formula is:

[0024]

[0025] Step eight 108: performing a polarization crosstalk test on the optical fiber sensitive ring to be tested under the temperature field;

[0026] The radial stress of the optical fiber sensitive ring under the temperature field is obtained by converting the polarization crosstalk test data, and the asymmetric refractive index distribution is corrected. result;

[0027] Step ten 110: dividing the data according to the length of each layer of the measured optical fiber sensitive ring;

[0028] Step 111: performing symmetry analysis of each layer / turn of the divided optical fiber sensitive ring under the temperature field;

[0029] Step 12 112: Firstly, the turn symmetry analysis of the sensitive loop is performed, and a layer of optical fiber data on a symmetrical length needs to be taken as a test unit;

[0030] Step 13 113: Then, the layer symmetry analysis of the sensitive ring is performed, and the number of layers of a winding pole on the symmetrical length needs to be taken as a test unit;

[0031] Step 14 114: align each test unit data according to layer / turn length;

[0032] Step 15 115: performing correlation analysis on the aligned unit data to obtain the correlation coefficient distribution of the test unit on the symmetric length;

[0033] Step 16 116: Accumulate the correlation coefficient of the test unit along the length of the optical fiber sensitive loop, and obtain the cumulative distribution of the correlation coefficient of the test unit along the length after integrating and summing;

[0034] Step 17 117: determine whether the correlation coefficient calculation of all test units on the optical fiber sensitive ring of this test has been completed at this temperature point, if not, execute step 18 118, if the correlation coefficient calculation of all test units on the optical fiber ring has been completed, execute step 19 119;

[0035] Step 18 118: If the cross-correlation analysis of all test units on the tested optical fiber ring has not been completed, after the calculation of the cumulative distribution of the correlation coefficient along the length of the previous test unit is completed, the next test unit is transferred to continue to perform the related operations of step 111 to step 16 116;

[0036] Step 19 119: After completing the correlation analysis and calculation of all test units, the correlation coefficients of all test units on the optical fiber sensitive ring are accumulated;

[0037] Step 20 120: Obtaining the equivalent coherence coefficient of the measured optical fiber sensitive ring at the temperature point;

[0038] Step 21 121: determine whether the current calculation is the last temperature point under the full-temperature test condition of the set temperature field. If it is not the last temperature point under the full-temperature test condition, execute the related operations of step 22 122. If the current calculation is the last temperature point under the full-temperature test condition, execute the related operations of step 23 123.

[0039] Step 22 122: If the current test is not the last temperature point in the full temperature test condition, switch to the next temperature point of the temperature field, and repeat the related operations from step 4 104 to step 20 120;

[0040] Step 23 123: If all tests at the set temperature points under the full-temperature test conditions have been completed, the full-temperature equivalent correlation coefficient distribution result can be obtained;

[0041] Step twenty-four 124: performing an outlier analysis on the full-temperature equivalent correlation coefficient of the optical fiber sensitive ring under temperature field excitation;

[0042] Step 25 125: Calculate the standard deviation of the full-temperature equivalent correlation coefficient of the optical fiber sensitive ring;

[0043] Finally, the physical symmetry analysis results of the overall optical fiber sensitive ring under temperature field are obtained.

[0044] The method for configuring the test conditions of the sensitive ring test temperature field in step 101 of claim 1 is as shown in the attached Figure 2 As shown, it is characterized in that the temperature field configuration method specifically includes the following steps:

[0045] Step 1 201: First, you need to prepare a temperature field control device for experimental testing, which can customize the high-precision temperature change curve;

[0046] Step 2 202: Setting the full temperature test range to -40°C to 70°C, i.e., the extreme environmental conditions that the optical fiber sensitive ring may reach during use;

[0047] Step 3 203: setting the interval between adjacent test temperature points of the temperature field to 5°C;

[0048] Step 4 204: Install the optical fiber sensitive ring to be tested in the temperature chamber in the air, ensure that the four sides are evenly heated and do not contact the inner wall of the temperature chamber, and avoid vibration and direct contact heat conduction to cause test errors;

[0049] Step 5 205: firstly, the temperature of the temperature field in the temperature box is lowered to the lowest temperature set by the full temperature test temperature curve, i.e. -40°C;

[0050] Step 6 206: Keep the temperature at this point for one hour to make the temperature inside the optical fiber sensitive ring evenly distributed, and then use a high-performance OFDR system to perform distributed characteristic parameter measurement;

[0051] Step 7 207: After the lowest temperature point test is completed, the temperature is increased by 5°C as a temperature point;

[0052] Step eight 208: After each temperature point reaches the set temperature, it is maintained at the set temperature for one hour, and then a high-precision distributed characteristic parameter measurement is performed using an OFDR system;

[0053] Step nine 209: After the full temperature test reaches the set maximum temperature of 70° C., keep the temperature for one hour, and measure the distributed characteristic parameters of the sensitive ring under the temperature field;

[0054] Step ten 210: the high-precision OFDR test system performs distributed characteristic parameter measurement of the optical fiber sensitive ring to be tested at 5° C. as a test temperature point during the full-temperature test;

[0055] The full temperature test of the optical fiber sensitive ring under the temperature field is completed.

[0056] The calculation process of the asymmetric refractive index distribution of the optical fiber sensitive ring as described in step 107 of claim 1 is as shown in the attached figure. Figure 4 As shown, the specific steps include:

[0057] Step 1 801: First, connect the pigtail of the clockwise winding direction of the optical fiber sensitive loop to be tested to the high-performance OFDR test system, and after starting the test, the detection light enters the optical fiber sensitive loop in the clockwise direction;

[0058] Step 2 802: Perform multi-parameter decoupling processing on the test data detected by the OFDR system along the optical fiber sensitive ring in the clockwise direction;

[0059] Step 3 803: Demodulate to obtain the temperature change in the sensitive ring under the temperature field and the reference temperature ;

[0060] Step 4 804: Simultaneously demodulate to obtain the axial thermal strain parameters of the sensitive ring under the temperature field ;

[0061] Step 5 805: Calculate the refractive index variation parameter of the sensitive ring during clockwise testing under the temperature field ;

[0062] Step 6 806: Connect the counterclockwise winding pigtail of the optical fiber sensitive loop to be tested to the high-performance OFDR test system, and after starting the test, the detection light enters the optical fiber sensitive loop in the counterclockwise direction;

[0063] Step 7 807: Perform multi-parameter decoupling processing on the test data detected by the OFDR system in the counterclockwise direction along the optical fiber sensitive ring;

[0064] Step 808: Demodulate to obtain the temperature change in the sensitive ring under the temperature field and the reference temperature ;

[0065] Step 9 809: Simultaneously demodulate to obtain the axial thermal strain parameters of the sensitive ring under the temperature field ;

[0066] Step 10 810: Calculate the refractive index variation parameter of the sensitive ring when testing counterclockwise under the temperature field ;

[0067] Step 11 811: Subtract the refractive index change parameters obtained from two different test directions to obtain the final asymmetric refractive index distribution data;

[0068] Compared with the prior art, the advantages of the present invention are:

[0069] The invention provides a quantitative method for measuring the physical symmetry of an optical fiber sensitive ring, and proposes an equivalent correlation coefficient to directly evaluate the physical symmetry of the optical fiber ring.

[0070] The method provided by the present invention, combined with data of high spatial resolution, can deeply evaluate the physical symmetry between layers and turns of an optical fiber ring, and realize the diagnosis of physical symmetry faults of an optical fiber ring.

[0071] The method provided by the present invention plays an important role in optimizing the winding process, evaluating the quality, and improving the yield of optical fiber rings. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a flow chart of a method for measuring the physical symmetry of a fiber optic sensitive ring under a temperature field;

[0073] Figure 2 It is the flow chart of temperature field configuration during full temperature test;

[0074] Figure 3 It is a structural diagram of a high-performance OFDR test system described in a method for measuring physical symmetry of an optical fiber sensitive ring under a temperature field;

[0075] Figure 4 Flow chart of calculation of asymmetric refractive index distribution of optical fiber sensitive ring

[0076] Figure 5 is the asymmetric refractive index distribution diagram of the optical fiber sensitive ring under the temperature field;

[0077] Figure 6 It is the correlation coefficient distribution diagram of the inter-turn unit of the optical fiber sensitive loop under the temperature field;

[0078] Figure 7 It is the summation result graph of the correlation coefficient of a unit on the sensitive ring along the length;

[0079] Figure 8 This is the final physical symmetry result diagram of a unit on the optical fiber sensitive ring under the temperature field. DETAILED DESCRIPTION

[0080] In order to clearly explain the method for measuring the physical symmetry of a fiber optic sensitive ring under a temperature field of the present invention, the following Figure 3 The present invention is further described, but the protection scope of the present invention should not be limited thereto.

[0081] The physical symmetry test device of the fiber optic gyroscope sensitive ring under temperature field is as shown in the attached figure. Figure 3 As shown, the selection of each device structure and the selection of component parameters are as follows:

[0082] The high-performance optical frequency domain reflectometry (OFDR) system is divided into the following four main components, including a light source module 3, an auxiliary interferometer module 4, a main interferometer module 5, a data acquisition and processing module 6, and a temperature field test module 7.

[0083] The light source 301 is a narrow linewidth tunable laser source, the wavelength scanning range is set to 10nm, the central wavelength is selected to be 1550nm, the scanning speed is 10nm / s, and the scanning time is 1s;

[0084] The maximum detection bandwidths of the first balanced photodetector 406, the second balanced photodetector 507 and the third balanced photodetector 508 are all 200 MHz;

[0085] The sampling frequency of acquisition card 601 is set to 125MHz / s;

[0086] The reference arm delay fiber 403 in the auxiliary interferometer 4 is set to 250m. The auxiliary interferometer 4 adopts a Michelson interferometer structure, and its arm length difference is 500m. The optical fiber used is a standard single-mode optical fiber with a refractive index n=1.456;

[0087] The splitting ratio of the first coupler 302 and the second coupler 501 is 1:99, and the splitting ratio of the third coupler 402 and the fourth coupler 504 is 50:50;

[0088] The optical fiber sensitive ring 702 to be tested is connected to the second port of the second circulator 503, and the first Bragg grating 701 is connected at the entrance of the optical fiber sensitive ring; at the same time, the second Bragg grating 703 is connected at the exit of the optical fiber sensitive ring to mark the pigtail position of the optical fiber sensitive ring to be tested;

[0089] The specific implementation method of the physical symmetry test method of the optical fiber sensitive ring under the temperature field of the present invention is as follows: the optical frequency domain distributed optical fiber sensitive ring characteristic parameter test sensing system is as follows: Figure 3 As shown, the continuous frequency-sweeping light emitted by the light source 301 is divided into two beams by the first coupler 302, and 99% of the light is injected into the main interferometer 5. In the main interferometer 5, the second coupler 501 injects 99% of the light into the arm where the second circulator 503 is located to ensure that the Rayleigh backscattered light has sufficient intensity. The optical fiber sensitive ring 702 to be tested is connected to the second port of the second circulator 503. 1% of the light in the first coupler 302 enters the auxiliary interferometer module 4 of the optical frequency domain reflection system to generate an auxiliary beat signal for characterizing the phase noise and compensation of the light source. The beat interference optical signals output by the main interferometer 5 and the auxiliary interferometer 4 are converted into electrical signals by the second balanced photodetector 507, the third balanced photodetector 508 and the first balanced photodetector 406, respectively, and then data is collected by the acquisition card 601, and finally sent to the computer 602 for subsequent processing of the signal using the method described in the present invention.

[0090] A method for measuring the physical symmetry of a fiber optic sensitive ring under a temperature field, the specific use process is as follows:

[0091] Step 1: First, the temperature field for the optical fiber sensitive ring test needs to be configured so that it meets the temperature field test conditions described in the method of the present invention;

[0092] Step 2: Use a high-performance optical frequency domain reflection system to measure the distributed characteristic parameters of the optical fiber sensitive ring in the temperature field;

[0093] Step 3: According to the test requirements, select several representative specific temperature points in the temperature field for subsequent testing;

[0094] Step 4: Perform multi-parameter simultaneous decoupling processing on the temperature and strain parameters in the distributed characteristic parameters obtained by the high-performance optical frequency domain reflection system test;

[0095] Step 5: Demodulate the distributed characteristic parameters to obtain the temperature change of the optical fiber sensitive ring in the applied temperature field;

[0096] Step 6: Demodulate the parameters obtained from the high-performance OFDR test to obtain the thermal strain generated by the optical fiber sensitive ring under the temperature field;

[0097] Step 7: Calculate the asymmetric refractive index of the winding body under thermal strain by using the distributed temperature and strain characteristic parameter data of the fiber sensitive ring obtained by multi-parameter decoupling First, calculate the change in refractive index under thermal strain The calculation formula is:

[0098]

[0099] in, is the standard refractive index, and is the photoelastic coefficient, is the axial thermal strain, is the thermo-optical coefficient of the optical fiber; the clockwise (CW) incident light in the optical fiber sensitive ring is disturbed by the external temperature at point s in the optical fiber sensitive ring, resulting in a refractive index change, which leads to a positive phase difference; similarly, the counterclockwise (CCW) incident light will also have a refractive index change at Ls, but a negative phase difference will be generated. Therefore, different refractive index changes are generated on the symmetrical length. By making a difference, we get an asymmetric distribution of the refractive index. The asymmetric refractive index distribution The calculation formula is:

[0100]

[0101] Step 8: Perform polarization crosstalk test on the optical fiber sensitive ring to be tested under the temperature field;

[0102] The radial stress of the optical fiber sensitive ring under the temperature field is obtained by converting the polarization crosstalk test data, and the asymmetric refractive index distribution is corrected. result;

[0103] Step 10: Divide the data according to the length of each layer of the measured optical fiber sensitive ring;

[0104] Step 11: Perform symmetry analysis of each layer / turn of the divided optical fiber sensitive ring under the temperature field;

[0105] Step 12: First, perform turn symmetry analysis on the sensitive loop, and take a layer of optical fiber data on a symmetrical length as a test unit;

[0106] Step 13: Then, the layer symmetry analysis of the sensitive ring is performed, and the number of layers of a winding pole on the symmetrical length needs to be taken as a test unit;

[0107] Step 14: Align each test unit data by layer / turn length;

[0108] Step 15: Perform correlation analysis on the aligned unit data to obtain the distribution of the correlation coefficient between the fiber sensitive loop turns under the temperature field. Figure 6 As shown;

[0109] Step 16: Accumulate the correlation coefficient of the test unit along the length of the optical fiber sensitive loop, and obtain the cumulative distribution of the correlation coefficient of the test unit along the length after integrating and summing. Figure 7 As shown;

[0110] Step 17: Determine whether the correlation coefficient calculation of all test units on the optical fiber sensitive ring of this test has been completed at this temperature point, if not, execute step 18 118, if the correlation coefficient calculation of all test units on the optical fiber ring has been completed, execute step 19 119;

[0111] Step 18: If the cross-correlation analysis of all test units on the tested optical fiber ring has not been completed, after the calculation of the cumulative distribution of the correlation coefficient along the length of the previous test unit is completed, the next test unit is transferred to continue to perform the related operations of step 111 to step 16 116;

[0112] Step 19: After completing the correlation analysis and calculation of all test units, the correlation coefficients of all test units on the optical fiber sensitive ring are accumulated;

[0113] Step 20: Obtain the equivalent coherence coefficient of the measured optical fiber sensitive ring at the temperature point;

[0114] Step 21: Determine whether this operation is the last temperature point under the full temperature test condition of the set temperature field. If it is not the last temperature point under the full temperature test condition, execute the relevant operation of step 22 122. If this operation is the last temperature point under the full temperature test condition, execute the relevant operation of step 23 123.

[0115] Step 22: If the current test is not the last temperature point in the full temperature test condition, switch to the next temperature point of the temperature field, and repeat the related operations from step 4 104 to step 20 120;

[0116] Step 23: If all tests at the set temperature points under the full-temperature test conditions have been completed, the full-temperature equivalent correlation coefficient distribution results can be obtained;

[0117] Step twenty-four 124: performing an outlier analysis on the full-temperature equivalent correlation coefficient of the optical fiber sensitive ring under temperature field excitation;

[0118] Step 25 125: Calculate the standard deviation of the full-temperature equivalent correlation coefficient of the optical fiber sensitive ring;

[0119] Finally, the physical symmetry analysis results of the overall optical fiber sensitive ring under the temperature field are obtained, such as Figure 8 shown.

Claims

1. A method for measuring the physical symmetry of an optical fiber sensitive ring under a temperature field. The method first requires the construction of a high-performance OFDR test system to test the distributed characteristic parameter (temperature and thermal strain) data of the optical fiber sensitive ring, and calculate the refractive index variable based on this data, and then perform layer turn symmetry analysis; the method for measuring the symmetry of an optical fiber sensitive ring under a temperature field is characterized in that: The method comprises the following steps: Step 1 (101): first, the temperature field for the optical fiber sensitive ring test needs to be configured so that it meets the temperature field full-temperature test conditions described in the method of the present invention; Step 2 (102): Use a high-performance optical frequency domain reflectometry system to perform distributed characteristic parameter measurement on the optical fiber sensitive ring in the temperature field; Step 3 (103): According to the test requirements, several representative specific temperature points in the temperature field are selected for subsequent testing; Step 4 (104): performing multi-parameter simultaneous decoupling processing on the temperature and strain parameters in the distributed characteristic parameters obtained by the high-performance optical frequency domain reflectometry system test; Step five (105): Demodulating the distributed characteristic parameters to obtain the temperature change of the optical fiber sensitive ring in the applied temperature field; Step six (106): Demodulating the parameters obtained from the high-performance OFDR test can obtain the thermal strain generated by the optical fiber sensitive ring under the temperature field; Step 7 (107): Calculate the asymmetric refractive index of the winding body under the action of thermal strain by using the distributed temperature and strain characteristic parameter data of the optical fiber sensitive ring obtained by multi-parameter decoupling. , first calculate the change in refractive index under thermal strain The calculation formula is: in, is the standard refractive index, and is the photoelastic coefficient, is the axial thermal strain, is the thermo-optical coefficient of the optical fiber; the clockwise (CW) incident light in the optical fiber sensitive ring is disturbed by the external temperature at point s in the optical fiber sensitive ring, resulting in a refractive index change, which leads to a positive phase difference; similarly, the counterclockwise (CCW) incident light will also have a refractive index change at Ls, but a negative phase difference will be generated. Therefore, different refractive index changes are generated on the symmetrical length. By making a difference, we get an asymmetric distribution of the refractive index. The asymmetric refractive index distribution The calculation formula is: Step eight (108): performing a polarization crosstalk test on the optical fiber sensitive ring to be tested under the temperature field; Step 9 (109): Calculate the radial stress of the optical fiber sensitive ring under the temperature field by converting the polarization crosstalk test data, and correct the asymmetric refractive index distribution. result; Step ten (110): dividing the data according to the length of each layer of the measured optical fiber sensitive ring; Step 11 (111): performing symmetry analysis of each layer / turn of the divided optical fiber sensitive ring under the temperature field; Step 12 (112): First, the turn symmetry analysis of the optical fiber ring is performed, and a layer of optical fiber data on a symmetrical length is taken as a test unit; Step 13 (113): Then, the layer symmetry analysis of the optical fiber ring is performed, and the number of layers of a winding pole on the symmetrical length needs to be taken as a test unit; Step fourteen (114): align each test unit data by layer / turn length; Step 15 (115): performing correlation analysis on the aligned unit data to obtain the correlation coefficient distribution of the test unit on the symmetric length; Step 16 (116): Accumulate the correlation coefficient of the test unit along the length of the optical fiber sensitive ring, and obtain the cumulative distribution of the correlation coefficient of the test unit along the length after performing integral summation; Step 17 (117): Determine whether the correlation coefficient calculation of all test units on the optical fiber sensitive ring has been completed at the temperature point. If not, execute step 18 (118); if the correlation coefficient calculation of all test units on the optical fiber sensitive ring has been completed, execute step 19 (119); Step 18 (118): If the correlation analysis of all test units on the tested optical fiber ring has not been completed, after completing the calculation of the cumulative distribution of the correlation coefficient along the length of the previous test unit, proceed to the next test unit and continue to perform the related operations of step 11 (111) to step 16 (116); Step 19 (119): After completing the correlation analysis and calculation of all test units, the correlation coefficients of all test units on the optical fiber sensitive ring are accumulated; Step 20 (120): Obtaining the equivalent correlation coefficient of the measured optical fiber sensitive ring at the temperature point; Step 21 (121): Determine whether this operation is the last temperature point under the full-temperature test condition of the set temperature field. If it is not the last temperature point under the full-temperature test condition, execute the relevant operation of step 22 (122). If this operation is the last temperature point under the full-temperature test condition, execute the relevant operation of step 23 (123); Step 22 (122): If the current test is not the last temperature point in the full temperature test condition, switch to the next temperature point of the temperature field and repeat the related operations from step 4 (104) to step 20 (120); Step 23 (123): If all tests at the set temperature points under the full-temperature test conditions have been completed, the full-temperature equivalent correlation coefficient distribution result can be obtained; Step twenty-four (124): performing an outlier analysis on the full-temperature equivalent correlation coefficient of the optical fiber sensitive ring under temperature field excitation; Step 25 (125): Calculate the standard deviation of the full-temperature equivalent correlation coefficient of the optical fiber sensitive ring; Finally, the physical symmetry analysis results of the overall optical fiber sensitive ring under temperature field are obtained.

Images