Gyroscope light path multi-parameter on-line monitoring device and method

Abstract

The present application provides a kind of on-line monitoring device and method of gyro optical path multi-quantity, including the device structure of implementation and the method flow of measurement.Its features are:injection wide spectrum light and sweep frequency light in the orthogonal polarization direction P and S in gyro optical path respectively, produce the reflection signal carrying temperature, strain and angular velocity information, signal is injected to gyro system and optical frequency domain reflectometer through coupler respectively and is tested, through the test timing of temperature box, 1xN optical switch, light source, optical frequency domain reflectometer, gyro system, the temperature, strain, angular velocity performance of multiple gyro optical path can be monitored simultaneously.The device uses the same light source, test structure and temperature box to test multiple gyro optical path simultaneously, ensures the test accuracy, greatly improves the test efficiency.The present application has the advantages of high integration degree, full test parameters, simple control mode, environmental interference resistance, etc., and can be widely used in gyro optical path performance monitoring and error compensation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical measurement technology and fiber-optic gyroscope, and particularly relates to a device and method for on-line monitoring of multiple parameters of a gyroscope optical path. BACKGROUND

[0002] The fiber-optic gyroscope is a non-mechanical angular velocity measuring instrument based on the Sagnac effect, which was invented in the 1970s. It plays an important role in the fields of aerospace, military, and sensing. The fiber-optic sensing ring, as the core component of the fiber-optic gyroscope system, its geometric symmetry and optical symmetry have a decisive influence on the thermal drift performance of the fiber-optic gyroscope. Therefore, it is imperative to measure and analyze the physical properties of the fiber itself.

[0003] The accurate measurement of the refractive index of the optical fiber is closely related to the accuracy of the distributed optical fiber sensing. In 2020, Yuan Li-Bo et al. (CN 110968048 A) of Guilin University of Electronic Technology invented a kind of orthogonal tilt three-core fiber grating parallel integrated Mach Zehnder interferometer. By detecting the output intensity after three-beam interference, the effective refractive index of N transmission modes in the fiber core can be calculated. In 2022, Liang Hui-Juan et al. (CN 114665957 A) of the 38th Research Institute of China Electronics Technology Group invented a kind of measurement system and method for the refractive index of the optical fiber. The vector network analyzer provides a sweep signal including different frequency signals to the electro-optical modulator. The optical signal modulated by the electro-optical modulator is transmitted through the optical fiber to be measured, and then demodulated by the detector to return to the vector network analyzer for analysis of the phase of different frequency signals. By further changing the length of the optical fiber to be measured and measuring again, the refractive index of the optical fiber to be measured can be calculated with high precision.

[0004] On the other hand, under the action of temperature field, thermal strain can exacerbate the deterioration of optical symmetry, and then trigger Mohr effect and Shupe effect, significantly increasing the thermal-induced drift in fiber-optic gyroscope system. Therefore, it is particularly important to accurately test and analyze the thermal strain of fiber-sensitive ring. In 2022, Liu Qingwen et al. (CN 117451203 A) of Shanghai Jiaotong University invented a large-range quasi-distributed optical fiber sensing method and system, which obtains the frequency value of the difference frequency term based on the beat frequency signal to calculate the optical path between two points, and obtains the temperature change and strain of the optical fiber by detecting the change of the optical path. In the same year, Wen Kunhua et al. (CN 115452213 A) of Guangdong University of Technology invented a distributed high-precision strain measurement method for fiber-sensitive ring under temperature change, which combines DTS and BOTDA systems, realizes temperature compensation for distributed stress testing of fiber-sensitive ring through calculation, determines the temperature stability of the internal stress distribution, and thus calculates the high-precision internal stress distribution of the fiber-sensitive ring. In 2023, Rao Yunjiang et al. (CN 116576897 A) of Zhijiang Laboratory invented a multi-parameter optical fiber distributed sensing system and method, which obtains the temperature or strain changes experienced by each fiber Bragg grating by the wavelength changes corresponding to the wavelength defects in the reflected spectrum of each fiber Bragg grating in the sensing optical fiber. In 2024, Dong Yongkang et al. (CN 118623781 A) of Harbin Institute of Technology invented an OPGW cable temperature strain decoupling method and device based on zero-strain reference point and ANN algorithm, which demodulates multiple Brillouin gain spectra using the temperature strain decoupling method based on zero-strain reference point to obtain the temperature value corresponding to each optical fiber, and realizes accurate data demodulation. Zhang Zhuo (Physical field analysis and coupling characteristics of marine fiber-optic gyroscope) of Harbin Engineering University analyzed the error mechanism of fiber-optic gyroscope physical field under the coupling action of temperature field and stress field, proposed the concepts of fiber ring temperature matrix, stress matrix and weight matrix, and deduced the traditional integral accumulation form of error model into the form of inner product of multiple matrices, which provides guidance for the design of fiber ring parameters, the selection of optical fiber and adhesive material, and improves the accuracy of the gyroscope.

[0005] In the field of fiber loop test technology, B-OTDA and optical frequency domain reflectometry (OFDR) are two commonly used methods. B-OTDA provides absolute measurement values, but its resolution needs to be improved, while OFDR has better resolution, but it is only a relative measurement relative to the reference state. Since internal stress has a significant impact on winding quality, some studies have used B-OTDA to monitor the symmetric stress of the fiber sensitive loop. Han Zhengying (Application of BOTDA fiber sensing technology in quality evaluation of fiber loop) of CETC 41 Institute used B-OTDA technology to measure the strain distribution of the fiber sensitive loop under different temperature conditions, and by selecting the winding body with more symmetric strain changes at each temperature, the performance of the gyro optical path was improved. Yang Jigang et al. (Research on the method of improving the quality of fiber winding body wound by winding machine) of Beijing Institute of Automation Control Equipment published a paper to solve the problem of asymmetric fiber tension during the process of inertial navigation loop winding. The strain data measured by B-OTDA was fed back to the tension control system in real time, thereby improving the stability and symmetry of tension control and significantly improving the symmetry of the sensitive loop. At the same time, OFDR technology based on Rayleigh scattering has developed rapidly in recent years. The OFDR system using the polarization maintaining scheme can test temperature and thermal strain simultaneously. A paper (Long-range high spatial resolution distributed temperature and strain sensing based on optical frequency-domain reflectometry) published by the University of Ottawa, Canada, proposed a corresponding test and demodulation scheme, which used the characteristics of negative temperature sensing coefficient and positive strain sensing coefficient to achieve a temperature resolution of ±0.8℃, a strain resolution of ±7.0με, and a spatial resolution of 1.3cm on a sensing distance of 170m. Yu Zhangjun et al. (Distributed Polarization Measurement for Fiber Sensing Coils: A Review) proposed a high-performance method for distributed polarization measurement of fiber sensing coils based on OFDR, which achieved a dynamic range >90dB, a measurement length >10km, a full-range spatial resolution <10cm, and time-domain, frequency-domain, and time-frequency-domain diagnosis, providing an important inspiration for our research.

[0006] But at present, on the basis of a large number of researches, the parameters affecting the thermal induced drift of the fiber ring and the change relation of these parameters under the environment are not clear, and there is a lack of suitable long distance, high precision, high spatial resolution temperature and thermal strain testing method, which seriously affects the measurement accuracy. Therefore, establishing a new transfer function of temperature to thermal induced drift and researching the multi-parameter testing method for temperature and thermal strain are of great significance for the parameter detection of fiber optic gyroscope and distributed fiber sensing application. SUMMARY

[0007] The purpose of the present application is to provide an OFDR beat frequency interference testing device with high precision, stability and reliability, and capable of measuring multiple parameters and multiple gyro optical paths simultaneously. The purpose of the present application is also to provide a testing method of the OFDR beat frequency interference testing device.

[0008] The online monitoring device for multiple parameters of a gyro optical path according to the present application comprises a TLS light source module 1, an auxiliary interferometer module 2, a main interferometer module 3, a to-be-measured module 4, a temperature control sensing module 5, a control and data processing module 6, and a fiber optic gyroscope angular velocity testing module 7. The temperature control sensing module 5 comprises a temperature box 501 and a temperature sensor 502. The control and data processing module 6 controls a TLS light source 101, a data acquisition card 603, the temperature box 501, the temperature sensor 502, N Y waveguide positive electrodes, N Y waveguide negative electrodes, an optical switch 410, and an SLD light source 701. The TLS light source module 1 injects a light beam into a first coupler 202, a part of the light is injected into the auxiliary interferometer module 2, and another part of the light is injected into the main interferometer module 3 from the s path via a 90° polarizer 204. The to-be-measured module 4 is connected to the main interferometer module 3 and the fiber optic gyroscope angular velocity testing module 7 and is placed in the temperature control sensing module 5. The auxiliary interference signal and the main interference signal are merged into the data acquisition card 603 and uploaded to a data processing machine for demodulation. A wide spectrum light is injected by the SLD light source 701, passes through a 0° polarizer 703, and is injected into the gyro optical path from the P path via a sixth coupler 707 and the optical switch 410. The return light returns to the gyro system 708 for detection and demodulation via a fifth coupler 308. By injecting wide spectrum light and sweep frequency light into the orthogonal polarization directions P and S in the gyro optical path respectively, spatial division multiplexing is realized in the gyro optical path, and the testing of multiple parameters of light, force, and heat is simultaneously performed.

[0009] The auxiliary interferometer module 2 comprises the first coupler 202, the 90° polarizer 204, a first circulator 207, a second coupler 209, a first Faraday rotating mirror 212, a second Faraday rotating mirror 213, and a first balanced photodetector 214. The light undergoes beat frequency interference at the second coupler 209.

[0010] (1) The first coupler left arm 215 is connected to the TLS light source 101 via a first flange 201.

[0011] (2) The 90° polarizer upper arm 217 is connected to the first coupler right upper arm 216 through the second flange plate 203.

[0012] (3) The first circulator A port 220 is connected to the first coupler right lower arm 219 through the fourth flange plate 206.

[0013] (4) The second coupler right upper arm 223 is connected to the first circulator B port 221 through the fifth flange plate 208.

[0014] (5) The second coupler right lower arm 226 and the first circulator C port 222 are connected to the first balanced photodetector 214 respectively.

[0015] (6) The first Faraday rotator mirror 212 is connected to the second coupler left upper arm 224 through the sixth flange plate 210.

[0016] (7) The second Faraday rotator mirror 213 is connected to the second coupler left lower arm 225 through the seventh flange plate 211.

[0017] The main interferometer module 3 comprises: a third coupler 302, a fourth coupler 306, a first polarization maintaining beam splitter 315, a second polarization maintaining beam splitter 319, a second balanced photodetector 321, a third balanced photodetector 325, and a fifth coupler 308. Light undergoes beat frequency interference at the fourth coupler 306.

[0018] (1) The third coupler right arm 301 is connected to the 90° polarizer lower arm 218 through the third flange plate 205.

[0019] (2) The fourth coupler right upper arm 305 is connected to the third coupler left upper arm 303 through the eighth flange plate 304.

[0020] (3) The fourth coupler right lower arm 311 is connected to the fifth coupler right upper arm 309 through the ninth flange plate 310.

[0021] (4) The first polarization maintaining beam splitter right arm 314 is connected to the fourth coupler left upper arm 312 through the tenth flange plate 313.

[0022] (5) The second polarization maintaining beam splitter right arm 318 is connected to the fourth coupler left lower arm 316 through the eleventh flange plate 317.

[0023] (6) The second balanced photodetector 321 is connected to the first polarization maintaining beam splitter left upper arm 320 and the second polarization maintaining beam splitter left upper arm 323 respectively.

[0024] (7) The third balanced photodetector 325 is connected to the first polarization maintaining beam splitter left lower arm 322 and the second polarization maintaining beam splitter left lower arm 324 respectively.

[0025] 1. The module to be tested 4 comprises: an optical switch 410, a second circulator 416, a third circulator

[0026] 418…an N+1th circulator 424, a first gyroscope optical path 430, a first input tail fiber 429, a second gyroscope optical path

[0027] 432, a second input tail fiber 431…an Nth gyroscope optical path 434, an Nth input tail fiber 433. The light is controlled by the optical switch 410 to flow through a certain gyroscope optical path to obtain its scattering spectrum.

[0028] (1) The optical switch 410 is a 1×N switch, comprising an optical switch input arm 402, an optical switch first output port 404, an optical switch second output port 411, an optical switch Nth output port 421 and an optical path converter 403. The use of an optical switch in one arm of the interferometer effectively reduces the influence of optical switch reflection.

[0029] (2) The optical switch input arm 402 is connected to the sixth coupler lower arm 714 through the twelfth flange 401.

[0030] (3) The second circulator A port 406 is connected to the optical switch first output port 404 through the thirteenth flange 405.

[0031] (4) The second circulator B port 408 is connected to the first input tail fiber 429 through the fourteenth flange 409.

[0032] (5) The second circulator C port 415 is connected to the fifth coupler first lower arm 328 through the fifteenth flange 407.

[0033] (6) The third circulator A port 413 is connected to the optical switch second output port 411 through the sixteenth flange 412.

[0034] (7) The third circulator B port 419 is connected to the second input tail fiber 431 through the seventeenth flange 420.

[0035] (8) The third circulator C port 417 is connected to the fifth coupler second lower arm 327 through the eighteenth flange 414.

[0036] (9) The Nth circulator A port 423 is connected to the optical switch Nth output port 421 through the nineteenth flange 422.

[0037] (10) The Nth circulator B port 427 is connected to the Nth input tail fiber 433 through the twentieth flange 428.

[0038] (11) The Nth circulator C port 426 is connected to the fifth coupler Nth lower arm 326 through the twenty-first flange 425.

[0039] 2. Temperature sensor 502 is placed in the oven 501. The first gyro optical path 430, the second gyro optical path 432, …, the Nth gyro optical path 434 are placed in the oven 501.

[0040] 3. The control and data processing module 6 includes: a control machine 601, a data processing machine 602, a data acquisition card 603.

[0041] (1) The first balanced photodetector 214 is connected to the data acquisition card 603 through the first electrical lead 604.

[0042] (2) The second balanced photodetector 321 is connected to the data acquisition card 603 through the second electrical lead 605.

[0043] (3) The third balanced photodetector 325 is connected to the data acquisition card 603 through the third electrical lead 606.

[0044] (4) The data acquisition card 603 is connected to the data processing machine 602 through the fourth electrical lead 607.

[0045] (5) The control machine 601 is connected to the data acquisition card 603 through the fifth electrical lead 608.

[0046] (6) The control machine 601 is connected to the temperature sensor 502 through the sixth electrical lead 609.

[0047] (7) The control machine 601 is connected to the oven 501 through the seventh electrical lead 610.

[0048] (8) The control machine 601 is connected to the optical switch 410 through the eighth electrical lead 611.

[0049] (9) The control machine 601 is connected to the TLS light source 101 through the ninth electrical lead 612.

[0050] (10) The control machine 601 is connected to the N Y waveguide positive electrodes and the N Y waveguide negative electrodes through the tenth electrical lead 613.

[0051] (11) The control machine 601 is connected to the SLD light source 701 through the eleventh electrical lead 614.

[0052] 4. The optical fiber gyro angular velocity test module 7 includes: an SLD light source 701, a 0° polarizer 703, an optical isolator 705, a sixth coupler 707, a gyro system 708.

[0053] (1) The 0° polarizer left arm 709 is connected to the SLD light source 701 through the twenty-second flange 702.

[0054] (2) The left arm 711 of the optical isolator is connected with the right arm 710 of the 0° polarizer through the 23rd flange 704.

[0055] (3) The right arm 712 of the optical isolator is connected with the left upper arm 713 of the sixth coupler through the 24th flange 706.

[0056] (4) The right upper arm 717 of the sixth coupler is connected with the left lower arm 307 of the third coupler through the 25th flange 716.

[0057] (5) The gyroscope system 708 is connected with the left upper arm 329 of the fifth coupler through the 26th flange 715.

[0058] 5. A test method for the on-line monitoring device of multiple parameters of a gyroscope optical path, characterized in that:

[0059] (1) In order to ensure the stability of the gyroscope optical path, the full-temperature environment test of the gyroscope optical path is performed.

[0060] (2) The first gyroscope optical path 430, the second gyroscope optical path 432, …, and the Nth gyroscope optical path 434 are connected in the test system to complete the optical path connection.

[0061] (3) The control machine 601 controls the TLS light source 101, the data acquisition card 603, the temperature box 501, the temperature sensor 502, the positive electrode of the Y waveguide, the negative electrode of the Y waveguide, the optical switch 410, and the SLD light source 701 to start synchronously for system self-checking.

[0062] (4) The gyroscope optical path is placed in the temperature box 501, and the control machine 601 sets the working curve of the temperature box, with the temperature range set as T1-T2 and the temperature change rate kept at T3 / min.

[0063] (5) The SLD light source 701 is turned on, and the gyroscope system 708 is tested in real time.

[0064] (6) The temperature box 501 is started, and the timing at this time is set as 0, and the control machine 601 starts timing, with the timing recorded every 1 min.

[0065] (7) The initial timing of the first gyroscope optical path 430, the second gyroscope optical path 432, …, and the Nth gyroscope optical path 434 is defined as 2, 3, …, N+1 respectively, and the current timing is judged.

[0066] (8) When the timing is 2, the optical switch 410 is switched to the first output port, and the control machine 601 triggers the TLS light source 101 and the data acquisition card 603 to test the first gyroscope optical path 430.

[0067] (9) When the time sequence is 3, the optical switch 410 is switched to the second output port, the control machine 601 triggers the TLS light source 101 and the data acquisition card 603, and the second gyro optical path 432 is tested.

[0068] (10) When the time sequence is N+1, the optical switch 410 is switched to the Nth output port, the control machine 601 triggers the TLS light source 101 and the data acquisition card 603, and the Nth gyro optical path 434 is tested.

[0069] (11) The test data is collected and uploaded to the data processing machine 602.

[0070] (12) The phase noise is compensated, and whether the intensity of the end reflection peak after compensation is consistent with the normal temperature is judged.

[0071] (13) If the intensity is consistent, the test of the first gyro optical path 430, the second gyro optical path 432,..., and the Nth gyro optical path 434 is completed, and the temperature sensor data corresponding to the time sequence is recorded.

[0072] (14) If the intensity is not consistent, the phase noise compensation is re-performed to make the intensity of the end reflection peak after compensation consistent with the normal temperature.

[0073] (15) Once the initial time sequence of each gyro optical path is increased by N, the test is performed.

[0074] (16) The test data of the P and S two paths is recorded, and the scattering spectrum signal is obtained after Fourier transformation.

[0075] (17) OFDR system strain demodulation.

[0076] (18) The gyro optical path strain data is obtained by correcting the influence of the thermal optical coefficient according to the temperature sensor data.

[0077] The purpose of the present application is to provide a device and method for improving the test efficiency, measuring multiple parameters in multiple gyro optical paths in one rapid temperature cycle, constructing an optical frequency domain test system, and measuring the influence of rapid temperature change on the relative thermal strain in a distributed optical fiber sensing system.

[0078] The online monitoring device for the multiple parameters of the gyro optical path provided by the present application is shown in FIG. 1. Figure 1 The device is characterized in that:

[0079] 1. The TLS light source 101, the first coupler 202, the 90° polarizer 204, the first circulator 207, the second coupler 209, the first Faraday rotator mirror 212, the second Faraday rotator mirror 213, the first balanced photodetector 214, the third coupler 302, the fifth circulator 901, the fourth coupler 306, the first polarization maintaining beam splitter 315, the second polarization maintaining beam splitter 319, the second balanced photodetector 321, the third balanced photodetector 325, and the device under test 902.

[0080] 2. The TLS light source 101 provides input light through the first coupler 202. 1% of the output light passes through the first connecting fiber 903 into the first circulator 207, and then enters the second coupler 209 through the first connecting fiber 904. The remaining 99% of the output light passes through the 90° polarizer 204 and the third connecting fiber 905 into the third coupler 302.

[0081] 3. The light entering the second coupler 209, 50% of which passes through the fourth connecting fiber 906 and is reflected by the first Faraday rotator mirror 212 to form the first reflected light 907, and the other 50% passes through the delay fiber 908 and is reflected by the second Faraday rotator mirror 213 to form the second reflected light 909. The first reflected light 907 and the second reflected light 909 interfere with each other at the second coupler 209. A part of the beat interference signal passes through the second connecting fiber 904, the first circulator B port, the first circulator C port, and the fifth connecting fiber 910 into the first balanced photodetector 214. Another part of the beat interference signal passes through the sixth connecting fiber 911 and also enters the first balanced photodetector 214. The two parts of the beat interference signal are differentially detected.

[0082] 4. The light entering the third coupler 302, 1% of which passes through the seventh connecting fiber 912 into the fourth coupler 306, and the other 99% passes through the eighth connecting fiber 913 and the fifth circulator 901, and then enters the device under test 902 from the fifth circulator A port and the fifth circulator B port through the ninth connecting fiber 914. The third reflected signal 915 passes through the ninth connecting fiber 914, the fifth circulator B port, the fifth circulator C port, and the tenth connecting fiber 916, and also enters the fourth coupler 306 to generate a beat interference signal.

[0083] 5. The beat interference signal generated at the fourth coupler 306, 50% of which passes through the eleventh connecting fiber 917 into the first polarization maintaining beam splitter 315, and the other 50% passes through the twelfth connecting fiber 918 into the second polarization maintaining beam splitter 319.

[0084] 6、The light entering the first polarization maintaining beam splitter 315, a part of which is input to the second balanced photoelectric detector 321 through the thirteenth connecting optical fiber 919, and another part of which is input to the third balanced photoelectric detector 325 through the fourteenth connecting optical fiber 920.

[0085] 7、The light entering the second polarization maintaining beam splitter 319, a part of which is input to the second balanced photoelectric detector 321 through the fifteenth connecting optical fiber 921, and another part of which is input to the third balanced photoelectric detector 325 through the sixteenth connecting optical fiber 922.

[0086] The flow chart of the gyro optical path temperature and strain test method is shown in Fig. 1. Figure 2 The gyro optical path temperature and strain test method has the following characteristics:

[0087] Step 801 is a full temperature environment test of the gyro optical path. The full temperature performance of the gyro optical path is tested under the temperature environment usually used by the gyro optical path system.

[0088] Step 802 is to connect the first gyro optical path, the second gyro optical path, …, the Nth gyro optical path in the test system to complete the optical path connection.

[0089] Step 803 is to use the control machine to control the TLS light source, the data acquisition card, the oven, the temperature sensor, the optical switch and the SLD light source to start synchronously for system self-checking.

[0090] Step 804 is to place the gyro optical path in the oven, and the control machine sets the working curve of the oven, the temperature range is T1-T2, and the temperature rate is kept at T3 / min.

[0091] Step 805 is to start the SLD light source, and the gyro system implements the test.

[0092] Step 806 is to start the oven, set the time sequence at this time as 0, and the control machine starts timing, and records the time sequence plus 1 every 1 min.

[0093] Step 807 is to define the initial time sequence of the first gyro optical path, the second gyro optical path, …, the Nth gyro optical path as 2, 3, …, N+1 respectively, and start judging the time sequence.

[0094] From step 808, if the time sequence reaches 2, step 816 is executed: the optical switch is switched to the first output port, and the control machine triggers the light source and the acquisition card, thereby testing the first gyro optical path.

[0095] From step 809, if the time sequence reaches 3, step 816 is executed: the optical switch is switched to the second output port, and the control machine triggers the light source and the acquisition card, thereby testing the second gyro optical path.

[0096] If the time sequence reaches N+1, step 816 is performed: the optical switch is switched to the Nth output port, the control machine triggers the light source and the data acquisition card, thereby testing the Nth gyro optical path.

[0097] Step 811 is to upload the test data collected by the data acquisition card to the data processing machine.

[0098] Step 812 is to compensate for the phase noise, and to determine whether the intensity of the end reflection peak after compensation is consistent with the normal temperature.

[0099] If the intensity of the end reflection peak after compensation is consistent with the normal temperature, step 813 is performed: the test of the first gyro optical path, the second gyro optical path,..., and the Nth gyro optical path is completed, and the temperature sensor data corresponding to the time sequence is recorded.

[0100] If the intensity of the end reflection peak after compensation is not consistent with the normal temperature, step 814 is performed: the phase noise compensation is performed again until the intensity of the end reflection peak after compensation is consistent with the normal temperature.

[0101] Step 815 is to perform a test once every N initial time sequences of each gyro optical path.

[0102] Step 816 is to record the test results of the P and S channels at different temperatures, and to obtain the scattering spectrum signal after Fourier transformation.

[0103] Step 817 is OFDR system strain demodulation. The cross-correlation calculation is performed on the reference signal and the test signal through the demodulation algorithm to obtain the Rayleigh scattering frequency shift of the fiber ring under temperature change.

[0104] Step 818 is to correct the influence of the thermal light coefficient according to the temperature sensor data, and to obtain the strain data of the gyro optical path.

[0105] The device and method for online monitoring of the gyro optical path based on OFDR proposed in the application have the basic principle of the working principle of the optical frequency domain reflectometer. The OFDR system formed by the interferometer is used to demodulate the internal reflection signal of the gyro optical path to obtain the frequency shift of the gyro optical path affected by temperature and strain.

[0106] Device test principle:

[0107] The OFDR system built can realize separate strain and temperature tests. Based on the P and S channel signals, the relationship between the frequency shift and temperature and strain obtained by the test is as follows

[0108]

[0109] In the formula: ε c is the strain coefficient of the cross-correlation frequency shift, T c is the temperature coefficient of the cross-correlation frequency shift.

[0110] It can be seen that the test result of OFDR includes strain and temperature simultaneously. The frequency shift obtained by using OFDR for testing includes the influence of temperature and strain simultaneously. The shift of the obtained spectrum is converted into corresponding temperature and strain values through temperature and strain coefficients.

[0111] Compared with the prior art, the present application has the following advantages:

[0112] 1. The present application realizes space division multiplexing in the gyro optical path by injecting wide spectrum light and sweep frequency light into orthogonal polarization directions P and S in the gyro optical path, and simultaneously tests multiple parameters of light, force and heat.

[0113] 2. The test device proposed in the present application can realize high-precision online monitoring of temperature, strain and angular velocity of the gyro optical path,

[0114] 3. The present application can monitor the performance of multiple gyro optical paths under temperature change simultaneously by designing a system timing control mode.

[0115] 4. The present application has simple structure, high testing precision, anti-environmental interference, effectively improves the testing efficiency, and can be widely used for performance monitoring and error compensation of the gyro optical path. BRIEF DESCRIPTION OF DRAWINGS

[0116] Figure 1 is a test principle diagram of optical frequency domain reflectometry (OFDR);

[0117] Figure 2 is a temperature and strain test method flowchart of the gyro optical path;

[0118] Figure 3 is a structure diagram of the gyro optical path to be tested;

[0119] Figure 4 is a full-temperature test method flowchart;

[0120] Figure 5 is a kind of online monitoring device diagram of the gyro optical path multiple parameters;

[0121] Figure 6 is a strain test result diagram of the gyro optical path. DETAILED DESCRIPTION

[0122] To clearly illustrate the device and method of the present application for online monitoring of the gyro optical path based on OFDR, the present application is further described in conjunction with the embodiments and drawings, but the protection scope of the present application should not be limited thereto.

[0123] Figure 3 is the structure of the gyro optical path to be tested of the present application. Its features are:

[0124] The to-be-tested gyroscope optical path structure is composed of a first gyroscope optical path 430, a first Y waveguide 851, a first optical fiber ring 854, a second gyroscope optical path 432, a second Y waveguide 857, a second optical fiber ring 860, an Nth gyroscope optical path 434, an Nth Y waveguide 863, and an Nth optical fiber ring 866. The first Y waveguide 851 comprises a first Y waveguide positive electrode 852 and a first Y waveguide negative electrode 853; the second Y waveguide 857 comprises a second Y waveguide positive electrode 858 and a second Y waveguide negative electrode 859; and the Nth Y waveguide 857 comprises an Nth Y waveguide positive electrode 864 and an Nth Y waveguide negative electrode 865.

[0125] When any one of the gyroscope optical paths is connected with the OFDR test system optical path, the light is divided into two paths after passing through the input tail fiber and the Y waveguide, and thus the fiber-optic gyroscope has clockwise transmission forward transmission light and counterclockwise transmission reverse transmission light. The control machine 601 can interfere and cancel the forward transmission light and the reverse transmission light of the fiber-optic gyroscope by applying a square wave with an amplitude of half the voltage of the Y waveguide and a frequency of the eigenfrequency to the two electrodes, thereby improving the test sensitivity. The forward transmission light and the reverse transmission light interfere with each other at the Y waveguide to carry the scattering information of the gyroscope optical path back to the OFDR test system optical path.

[0126] Meanwhile, the SLD light source 701 injects broadband light, which is injected into the same gyroscope optical path from the P path via the sixth coupler 707 and the optical switch 410 after passing through the 0° polarizer 703, and the return light returns to the gyroscope system 708 for detection and demodulation via the fifth coupler 308.

[0127] In combination with Figure 4 The full-temperature test method is as follows:

[0128] Step 819 is to set the temperature range of the high-low temperature box to T1-T2, and set the temperature change rate to 1℃ / min.

[0129] Step 820 is to place the gyroscope optical path in the temperature box, and keep the gyroscope optical path on four sides.

[0130] Step 821 is to keep the gyroscope optical path at a temperature T3 for 30 min.

[0131] Step 822 is to lower the temperature of the temperature box from T3 to T1 at a rate of 1℃ / min.

[0132] Step 823 is to keep the gyroscope optical path at a temperature T1 for 60 min.

[0133] Step 824 is to raise the temperature of the temperature box from T1 to T2 at a rate of 1℃ / min.

[0134] Step 825 is to keep the gyroscope optical path at a temperature T2 for 60 min.

[0135] Step 826 is that the OFDR system tests every 5 minutes.

[0136] Figure 5 It is a kind of on-line monitoring device diagram of gyro optical path multi-parameters, including TLS light source module 1, auxiliary interferometer module 2, main interferometer module 3, to be measured module 4, temperature control sensing module 5, control and data processing module 6 and optical fiber gyro angular velocity test module 7. Figure 3 The to-be-measured module 4 has the same structure as that of the N to-be-measured gyro optical paths.

[0137] In combination with Figure 5 An embodiment of the present application is that the sweep frequency range of the TLS light source 101 is set to 10nm-160nm, the sweep frequency speed is 10nm / s, and the emitted sweep frequency light is respectively 1% into the auxiliary interferometer module 2 and 99% into the main interferometer module 3 by the first coupler 202.

[0138] The light entering the main interferometer module 3 is respectively 1% through the third coupler left upper arm 303 and the fourth coupler right upper arm 305 into the fourth coupler 306, and the other 99% through the third coupler left lower arm 307 and the sixth coupler lower arm 714 into the optical switch 410.

[0139] The 1% light through the third coupler left upper arm 303 and the fourth coupler right upper arm 305 is used as a reference signal, and the 99% light through the third coupler left lower arm 307 and the sixth coupler lower arm 714 into the optical switch 410 and a certain gyro optical path is used as a test signal. After the beat frequency interference of the two signals at the fourth coupler 306, the data acquisition card 603 with a sampling frequency of 180MHz receives.

[0140] The control machine 601 performs opening and closing operations on the 1xN optical switch 410 N output ports.

[0141] If the current timing is a value in the arithmetic sequence with the first term 2 and the common difference N, then the optical switch is switched to the first output port 404, the control machine 601 triggers the TLS light source 101 and the data acquisition card 603, and the first gyro optical path 430 is tested.

[0142] If the current timing is a value in the arithmetic sequence with the first term 3 and the common difference N, then the optical switch is switched to the second output port 411, the control machine 601 triggers the TLS light source 101 and the data acquisition card 603, and the second gyro optical path 432 is tested.

[0143] If the current timing is a value in the arithmetic sequence with the first term N+1 and the common difference N, then the optical switch is switched to the Nth output port 421, the control machine 601 triggers the TLS light source 101 and the data acquisition card 603, and the Nth gyro optical path 434 is tested.

[0144] When any one of the gyro optical paths is connected with the OFDR test system optical path, the light is divided into two paths after passing through the input pigtail and the Y waveguide, so that the fiber optic gyroscope has clockwise transmission of the forward transmission light and counterclockwise transmission of the reverse transmission light. The control machine 601 can interfere and cancel the forward transmission light and the reverse transmission light of the fiber optic gyroscope by applying a square wave with an amplitude of half the wave voltage of the Y waveguide and a frequency of the intrinsic frequency to the two electrodes, so as to improve the test sensitivity. The forward and reverse transmission lights interfere with each other at the Y waveguide, and carry the scattering information of the gyro optical path back to the OFDR test system optical path.

[0145] Meanwhile, the SLD light source 101 selects a wide-spectrum light source with a center wavelength of 1550 nm±20 nm and a spectral width of ≥40 nm, passes through the 0° polarizer 703, and is injected into the same gyro optical path from the P path through the sixth coupler 707 and the optical switch 410. The return light returns to the gyro system 708 for detection and demodulation through the fifth coupler 308 with a splitting ratio of 50:50, and the fiber optic gyro angular velocity is obtained.

[0146] Collect test data. The data uploaded to the data processing machine are compensated for phase noise, and it is judged whether the intensity of the end reflection peak after compensation is consistent with the normal temperature. If consistent, the test of the gyro optical path is completed, and the temperature sensor data corresponding to the timing is recorded. If not consistent, re-compensate for the phase noise until the intensity of the end reflection peak after compensation is consistent with the normal temperature.

[0147] Record the test data of P and S two paths, and obtain the scattering spectrum signal after Fourier transformation.

[0148] OFDR system strain demodulation. The cross-correlation calculation is performed on the reference signal and the test signal by the demodulation algorithm to obtain the Rayleigh scattering frequency shift of the gyro optical path under temperature change.

[0149] According to the temperature sensor data, the influence of the thermal light coefficient is corrected, and thus the strain data of the gyro optical path are obtained. The test results of the strain of the gyro optical path are shown in Figure 6 It can be seen that the spatial resolution of the gyro optical path multi-parameter test device based on OFDR is 5 cm, and the strain resolution is ±1με.

Claims

1. An online monitoring device for multiple parameters of a gyroscope optical path, characterized in that: The TLS light source module (1), the auxiliary interferometer module (2), the main interferometer module (3), the module to be measured (4), the temperature control sensing module (5), the control and data processing module (6) and the fiber-optic gyroscope angular velocity test module (7) are included; the temperature control sensing module (5) includes: a temperature box (501), a temperature sensor (502); the control and data processing module (6) controls the TLS light source (101), the data acquisition card (603), the temperature box (501), the temperature sensor (502), N Y waveguide positive electrodes, N Y waveguide negative electrodes, an optical switch (410) and an SLD light source (701); the TLS light source module (1) injects a light beam into the first coupler (202), part of the light is injected into the auxiliary interferometer module (2), and the other part of the light is injected into the main interferometer module (3) from the s path via the 90° polarizer (204); the module to be measured (4) is connected with the main interferometer module (3) and the fiber-optic gyroscope angular velocity test module (7) respectively and is put into the temperature control sensing module (5), the auxiliary interference signal and the main interference signal are merged into the data acquisition card (603) and uploaded to the data processing machine for demodulation; the SLD light source (701) injects wide-spectrum light, the light passes through the 0° polarizer (703), is injected into the gyroscope light path from the P path via the sixth coupler (707) and the optical switch (410), and the return light returns to the gyroscope system (708) for detection and demodulation; by injecting wide-spectrum light and sweep-frequency light into the orthogonal polarization directions P and S in the gyroscope light path respectively, space division multiplexing is realized in the gyroscope light path, and the testing of multiple parameters such as light, force and heat is simultaneously performed; The auxiliary interferometer module (2) includes a first coupler (202), a 90° polarizer (204), a first circulator (207), a second coupler (209), a first Faraday rotating mirror (212), a second Faraday rotating mirror (213) and a first balanced photodetector (214); the light generates beat interference in the second coupler (209); (1) The first coupler left arm (215) is connected with the TLS light source (101) through the first flange (201); (2) The 90° polarizer upper arm (217) is connected with the first coupler right upper arm (216) through the second flange (203); (3) The first circulator A port (220) is connected with the first coupler right lower arm (219) through the fourth flange (206); (4) The second coupler right upper arm (223) is connected with the first circulator B port (221) through the fifth flange (208); (5) The second coupler right lower arm (226) and the first circulator C port (222) are connected with the first balanced photodetector (214) respectively; (6) The first Faraday rotating mirror (212) is connected with the second coupler left upper arm (224) through the sixth flange (210); (7) The second Faraday rotating mirror (213) is connected with the second coupler left lower arm (225) through the seventh flange (211); The main interferometer module (3) comprises: a third coupler (302), a fourth coupler (306), a first polarization maintaining beam splitter (315), a second polarization maintaining beam splitter (319), a second balanced photodetector (321), a third balanced photodetector (325), a fifth coupler (308); the light is beat frequency interfered in the fourth coupler (306); (1) the third coupler right arm (301) is connected with the 90° polarizer lower arm (218) through the third flange (205); (2) the fourth coupler right upper arm (305) is connected with the third coupler left upper arm (303) through the eighth flange (304); (3) the fourth coupler right lower arm (311) is connected with the fifth coupler right upper arm (309) through the ninth flange (310); (4) the first polarization maintaining beam splitter right arm (314) is connected with the fourth coupler left upper arm (312) through the tenth flange (313); (5) the second polarization maintaining beam splitter right arm (318) is connected with the fourth coupler left lower arm (316) through the eleventh flange (317); (6) the second balanced photodetector (321) is connected with the first polarization maintaining beam splitter left upper arm (320) and the second polarization maintaining beam splitter left upper arm (323) respectively; (7) the third balanced photodetector (325) is connected with the first polarization maintaining beam splitter left lower arm (322) and the second polarization maintaining beam splitter left lower arm (324) respectively.

2. The device according to claim 1, characterized in that The to-be-measured module (4) comprises: an optical switch (410), a second circulator (416), a third circulator (418), an N+1th circulator (424), a first gyro optical path (430), a first input tail fiber (429), a second gyro optical path (432), a second input tail fiber (431), an Nth gyro optical path (434), and an Nth input tail fiber (433); the light is controlled to flow through a certain gyro optical path by the optical switch (410) to obtain a scattering spectrum thereof; (1) the optical switch (410) is a 1×N switch, comprising an optical switch input arm (402), an optical switch first output port (404), an optical switch second output port (411), an optical switch Nth output port (421), and an optical path converter (403); the influence of optical switch reflection is effectively reduced in the mode of using the optical switch in one arm of the interferometer; (2) the optical switch input arm (402) is connected with the sixth coupler lower arm (714) through the twelfth flange (401); (3) the second circulator A port (406) is connected with the optical switch first output port (404) through the thirteenth flange (405); (4) the second circulator B port (408) is connected with the first input tail fiber (429) through the fourteenth flange (409); (5) the second circulator C port (415) is connected with the fifth coupler first lower arm (328) through the fifteenth flange (407); (6) the third circulator A port (413) is connected with the optical switch second output port (411) through the sixteenth flange (412); (7) the third circulator B port (419) is connected with the second input tail fiber (431) through the seventeenth flange (420); (8) The third circulator C port (417) is connected with the fifth coupler second lower arm (327) through the eighteenth flange (414); (9) The Nth circulator A port (423) is connected with the optical switch Nth output port (421) through the nineteenth flange (422); (10) The Nth circulator B port (427) is connected with the Nth input tail fiber (433) through the twentieth flange (428); (11) The Nth circulator C port (426) is connected with the fifth coupler Nth lower arm (326) through the twenty-first flange (425).

3. The device according to claim 1, characterized in that The temperature sensor (502) is placed in the oven (501); the first gyro optical path (430), the second gyro optical path (432), and the Nth gyro optical path (434) are all placed in the oven (501).

4. The device according to claim 1, characterized in that The control and data processing module (6) comprises a control machine (601), a data processing machine (602), and a data acquisition card (603); (1) The first balanced photodetector (214) is connected with the data acquisition card (603) through the first electric lead (604); (2) The second balanced photodetector (321) is connected with the data acquisition card (603) through the second electric lead (605); (3) The third balanced photodetector (325) is connected with the data acquisition card (603) through the third electric lead (606); (4) The data acquisition card (603) is connected with the data processing machine (602) through the fourth electric lead (607); (5) The control machine (601) is connected with the data acquisition card (603) through the fifth electric lead (608); (6) The control machine (601) is connected with the temperature sensor (502) through the sixth electric lead (609); (7) The control machine (601) is connected with the oven (501) through the seventh electric lead (610); (8) The control machine (601) is connected with the optical switch (410) through the eighth electric lead (611); (9) The control machine (601) is connected with the TLS light source (101) through the ninth electric lead (612); (10) The control machine (601) is connected with the N Y waveguide positive electrodes and the N Y waveguide negative electrodes through the tenth electric lead (613); (11) The control machine (601) is connected with the SLD light source (701) through the eleventh electric lead (614).

5. The device according to claim 1, characterized in that The optical fiber gyro angular velocity test module (7) comprises an SLD light source (701), a 0° polarizer (703), an optical isolator (705), a sixth coupler (707), and a gyro system (708); (1) The 0° polarizer left arm (709) is connected with the SLD light source (701) through the twenty-second flange (702); (2) The optical isolator left arm (711) is connected with the 0° polarizer right arm (710) through the twenty-third flange (704); (3) The optical isolator right arm (712) is connected with the sixth coupler left upper arm (713) through the twenty-fourth flange (706); (4) The sixth coupler right upper arm (717) is connected with the third coupler left lower arm (307) through the twenty-fifth flange (716); (5) The gyro system (708) is connected with the fifth coupler left upper arm (329) through the twenty-sixth flange (715).

6. The test method of the on-line monitoring device of the multi-parameter of the gyro optical path according to claim 1, characterized in that: (1) In order to ensure the stability of the gyro optical path, the full-temperature environment test of the gyro optical path is carried out; (2) The first gyro optical path (430), the second gyro optical path (432), …, the Nth gyro optical path (434) are connected in the test system, and the optical path connection is completed; (3) The control machine (601) controls the TLS light source (101), the data acquisition card (603), the temperature box (501), the temperature sensor (502), the Y waveguide positive electrode, the Y waveguide negative electrode, the optical switch (410) and the SLD light source (701) to start synchronously for system self-checking; (4) The gyro optical path is placed in the temperature box (501), the control machine (601) sets the working curve of the temperature box, the temperature range is set as T1-T2, and the temperature change rate is kept at T3 / min; (5) The SLD light source (701) is turned on, and the gyro system (708) is tested in real time; (6) The temperature box (501) is started, the time sequence at this time is set as 0, and the control machine (601) starts timing, and records the time sequence by 1 every 1 min; (7) The initial time sequences of the first gyro optical path (430), the second gyro optical path (432), …, the Nth gyro optical path (434) are defined as 2, 3, …, N+1 respectively, and the current time sequence is judged; (8) When the time sequence is 2, the optical switch (410) is switched to the first output port, the control machine (601) triggers the TLS light source (101) and the data acquisition card (603), and the first gyro optical path (430) is tested; (9) When the time sequence is 3, the optical switch (410) is switched to the second output port, the control machine (601) triggers the TLS light source (101) and the data acquisition card (603), and the second gyro optical path (432) is tested; (10) When the time sequence is N+1, the optical switch (410) is switched to the Nth output port, the control machine (601) triggers the TLS light source (101) and the data acquisition card (603), and the Nth gyro optical path (434) is tested; (11) The test data is collected and uploaded to the data processing machine (602); (12) The phase noise is compensated, and whether the intensity of the end reflection peak after compensation is consistent with the normal temperature is judged; (13) If the intensity is consistent, the test of the first gyro optical path (430), the second gyro optical path (432), …, the Nth gyro optical path (434) is completed, and the temperature sensor data corresponding to the time sequence is recorded; (14) If the intensity is not consistent, the phase noise compensation is re-performed, so that the intensity of the end reflection peak after compensation is consistent with the normal temperature; (15) The initial time sequence of each gyro optical path is increased by N, and the test is performed once; (16) The P and S test data are recorded, and the scattering spectrum signal is obtained after Fourier transformation; (17) The OFDR system is strain demodulated; (18) Correcting the thermal-optical coefficient effect on the gyro optical path strain data according to the temperature sensor data.

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