Multi-parameter testing device and method for multiple optical fiber sensitive rings

Abstract

The invention provides a multi-parameter testing device and a multi-parameter testing method for a plurality of optical fiber sensitive rings. The multi-parameter testing device comprises an implemented device structure and a testing method flow. The method is characterized by comprising the following steps: injecting sweep frequency light into a device to be tested, generating a reflection signal carrying temperature and strain information, injecting the reflection signal into an optical frequency domain reflectometer for testing, and controlling the testing time sequence of an incubator, a 1 * N optical switch, a sweep frequency laser and the optical frequency domain reflectometer. And multi-parameter performance of a plurality of optical fiber rings under temperature change can be tested at the same time. According to the device, a plurality of optical fiber rings are tested by using the same light source, the same test structure and the same temperature box at the same time, the test precision is ensured, and the test efficiency is greatly improved. The device has the advantages of high integration degree, complete test parameters, simple control mode, environmental interference resistance and the like, and can be widely applied to high-precision measurement and analysis of multi-parameter performance of optical devices such as polarization maintaining optical fibers, optical fiber rings, hydrophones and the like.

Description

Technical Field

[0001] The invention relates to the field of optical measurement technology and fiber optic gyroscope, and in particular to a multi-parameter testing device and method for multiple fiber optic sensitive rings. Background Art

[0002] Fiber optic gyroscope is a non-mechanical angular velocity measuring instrument based on Sagnac effect invented in the 1970s. It plays an important role in the fields of aerospace, military, and sensing. As the core component of the fiber optic gyroscope system, the geometric symmetry and optical symmetry of the fiber optic sensitive ring 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 optical fiber itself.

[0003] The precise measurement of the refractive index of optical fiber is closely related to the accuracy of distributed optical fiber sensing. In 2020, Yuan Libo and others from Guilin University of Electronic Technology (CN 110967048 A) invented an orthogonal tilted three-core fiber Bragg grating parallel integrated MachZehnder interferometer. By detecting the output intensity after the interference of three beams, the effective refractive index of the transmission mode in N fiber cores can be calculated. In 2022, Liang Huijuan and others from the 38th Institute of China Electronics Technology Group Corporation (CN 114665957 A) invented a system and method for measuring the refractive index of optical fiber. A vector network analyzer is used to provide a sweeping signal including signals of different frequencies to the optoelectronic modulator, which is modulated into an optical signal by the optoelectronic modulator and transmitted through the optical fiber to be tested. After that, it is demodulated by the detector and returned to the vector network analyzer to analyze the phase of signals of different frequencies. The length of the optical fiber to be tested is further changed and measured again, thereby achieving high-precision calculation of the refractive index of the optical fiber to be tested.

[0004] On the other hand, under the action of temperature field, thermal strain will aggravate the deterioration of optical symmetry, thereby inducing Mohr effect and Shupe effect, significantly aggravating the thermal drift in the fiber optic gyroscope system. Therefore, it is particularly important to accurately test and analyze the thermal strain of the fiber optic sensitive ring. In 2022, Liu Qingwen et al. (CN 117451203 A) from Shanghai Jiaotong University invented a large-scale quasi-distributed fiber optic sensing method and system. The frequency value of the difference frequency term is obtained based on the beat frequency signal to calculate the optical path between two points, and the temperature change and strain of the optical fiber are obtained by detecting the change in the optical path. In the same year, Wen Kunhua et al. (CN 115452213 A) from Guangdong University of Technology invented a distributed high-precision strain measurement method for fiber optic sensitive rings under temperature variation conditions. It combines DTS and BOTDA systems, realizes temperature compensation of distributed stress test of fiber optic sensitive rings by inference, determines the temperature stability of its internal stress distribution, and thus infers the high-precision internal stress distribution of fiber optic sensitive rings. In 2023, Rao Yunjiang et al. (CN 116576897 A) from Zhijiang Laboratory invented a multi-parameter fiber-optic distributed sensing system and method thereof, which obtains the temperature or strain changes felt by each fiber Bragg grating in the sensing fiber by sensing the wavelength changes corresponding to the wavelength defects in the reflection spectrum of each fiber Bragg grating. In 2024, Dong Yongkang et al. (CN118623781 A) from Harbin Institute of Technology invented a method and device for decoupling temperature and strain of OPGW optical cables based on zero strain reference point and ANN algorithm, and used the temperature-strain decoupling method based on zero strain reference point to demodulate multiple Brillouin gain spectra, obtain the corresponding temperature value of each optical fiber, and realize accurate data demodulation. Zhang Zhuo from Harbin Engineering University (Physical Field Analysis and Coupling Characteristics of Marine Fiber Optic Gyroscopes) analyzed the physical field error mechanism of fiber optic gyroscopes under the coupling of temperature field and stress field, proposed the concepts of fiber optic ring temperature matrix, stress matrix, and weight matrix, and derived the traditional integral accumulation error model into the form of inner products of multiple matrices, providing guidance for the design of fiber optic ring parameters and the selection of optical fiber and solid adhesive materials, thereby improving the accuracy of gyroscopes.

[0005] In terms of fiber optic ring testing technology, B-OTDA and optical frequency domain reflectometry (OFDR) are two commonly used methods. B-OTDA provides absolute measurements, but its resolution needs to be improved. On the contrary, 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 symmetrical stress of fiber optic sensitive rings. Han Zhengying of China Electronics 41 Research Institute (Application of BOTDA fiber optic sensing technology in fiber optic ring quality assessment) used B-OTDA technology to measure the strain distribution of fiber optic sensitive rings under different temperature conditions, and improved the performance of the gyro optical path by screening winding bodies with relatively symmetrical strain changes at each temperature. Yang Jigang and others from Beijing Institute of Automation and Control Equipment published (Research on methods to improve the quality of winding bodies of fiber optic winding bodies). In response to the problem of asymmetric fiber tension during inertial navigation ring 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 sensitive rings. 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 simultaneously test temperature and thermal strain. The University of Ottawa in Canada published a paper (Long-range high spatial resolution distributed temperature and strain sensing based on optical frequency-domain reflectometry) proposing a corresponding test and demodulation scheme. By using the characteristics of negative temperature sensing coefficient and positive strain sensing coefficient, it achieved a temperature resolution of ±0.8°C and a thermal strain resolution of ±7.0°C at a sensing distance of 170m. The strain resolution and spatial resolution of 1.3 cm

[74] . Yu Zhangjun et al. published a paper (Distributed Polarization Measurement for Fiber Sensing Coils: A Review) in which they proposed a high-performance method to obtain a dynamic range of >90 dB, a measurement length of >10 km, a full-range spatial resolution of <10 cm, and time domain, frequency domain, and time-frequency domain diagnosis in the distributed polarization measurement of fiber sensing coils based on OFDR, which provided important inspiration for our research.

[0006] However, based on a large number of studies, the parameters that affect the thermal drift of the fiber ring and the relationship between the changes of these parameters in the environment are unclear. At the same time, there is a lack of suitable long-distance, high-precision, and high-spatial resolution temperature and thermal strain test methods, which seriously affects its measurement accuracy. Therefore, establishing a new transfer function from temperature to thermal drift and studying multi-parameter test methods for temperature and thermal strain are extremely important for parameter detection of fiber optic gyroscopes and distributed fiber optic sensing applications. Summary of the invention

[0007] The purpose of the present invention is to provide an OFDR beat frequency interferometer test device with high accuracy, stability and reliability, multi-parameter measurable, and simultaneous measurement of multiple optical fiber rings. The purpose of the present invention is also to provide a test method for the OFDR beat frequency interferometer test device.

[0008] The multi-parameter test device of a multi-branch optical fiber sensitive ring of the present invention is characterized by comprising a TLS light source module 1, an auxiliary interferometer module 2, a main interferometer module 3, a module to be tested 4, a temperature control sensor module 5 and a control and data processing module 6. 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 and the optical switch 410. The TLS light source module 1 injects the light beam into the first coupler 204, a 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. The module to be tested 4 is connected to the main interferometer module 3 and placed in the temperature control sensor module 5. The auxiliary interference signal and the main interference signal are integrated into the data acquisition card 603, and finally the scattering and reflection characteristics of the device to be tested are obtained.

[0009] 1. A multi-parameter test device for multiple fiber sensitive rings according to claim 1, characterized in that the auxiliary interferometer module 2 comprises: a 45° polarizer 202, a first coupler 204, a first circulator 207, a second coupler 209, a first Faraday rotator 212, a second Faraday rotator 213, and a first balanced photodetector 214. Light undergoes beat frequency interference in the second coupler 209.

[0010] (1) The 45° polarizer 202 is connected to the TLS light source 101 through the first flange 201.

[0011] (2) The left arm 218 of the first coupler is connected to the 45° polarizer 202 through the second flange 203.

[0012] (3) The first circulator A port 221 is connected to the first coupler right lower arm 220 through the fourth flange 206.

[0013] (4) The second coupler right upper arm 224 is connected to the first circulator B port 222 through the fifth flange 208.

[0014] (5) The second coupler right lower arm 215 and the first circulator C port 223 are respectively connected to the first balanced photodetector 214.

[0015] (6) The first Faraday rotation mirror 212 is connected to the second coupler left upper arm 225 via the sixth flange 210 .

[0016] (7) The second Faraday rotation mirror 213 is connected to the second coupler left lower arm 226 via the seventh flange 211 .

[0017] (8) The first optical fiber 216, the second optical fiber 217, the third optical fiber 218, and the fourth optical fiber 219 are all polarization-maintaining optical fibers.

[0018] (9) The sixth optical fiber 221 , the seventh optical fiber 222 , the eighth optical fiber 223 , the ninth optical fiber 224 , the tenth optical fiber 215 , the eleventh optical fiber 225 , and the delay optical fiber 226 are all single-mode optical fibers.

[0019] 2. The multi-parameter test device of a multi-branch optical fiber sensitive ring according to claim 1, characterized in that 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 in the fourth coupler 306.

[0020] (1) The third coupler right arm 301 is connected to the first coupler right upper arm 219 through the third flange 205 .

[0021] (2) The fourth coupler right upper arm 305 is connected to the third optical coupler left upper arm 303 through the eighth flange 304 .

[0022] (3) The fourth coupler right lower arm 311 is connected to the optical fifth coupler upper arm 309 through the ninth flange 310 .

[0023] (4) The right arm 314 of the first polarization-maintaining beam splitter is connected to the upper left arm 312 of the fourth coupler through the tenth flange 313 .

[0024] (5) The right arm 318 of the second polarization-maintaining beam splitter is connected to the left lower arm 316 of the fourth coupler through the eleventh flange 317.

[0025] (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.

[0026] (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.

[0027] (8) The twelfth optical fiber 301, the thirteenth optical fiber 303, the fourteenth optical fiber 307, the fifteenth optical fiber 305, the sixteenth optical fiber 311, the seventeenth optical fiber 312, the eighteenth optical fiber 316, the nineteenth optical fiber 314, the twentieth optical fiber 318, the twenty-first optical fiber 320, the twenty-second optical fiber 322, the twenty-third optical fiber 323, the twenty-fourth optical fiber 324, the twenty-fifth optical fiber 326, the twenty-sixth optical fiber 327, the twenty-seventh optical fiber 328, and the twenty-eighth optical fiber 309 are all polarization-maintaining optical fibers.

[0028] 3. A multi-parameter test device for a multi-branch optical fiber sensitive ring according to claim 1, characterized in that the module to be tested 4 comprises: an optical switch 410, a second circulator 416, a third circulator 418 ... an Nth circulator 424, a first optical fiber ring to be tested 429, a first right-side pigtail 432, a first left-side pigtail 435, a second optical fiber ring to be tested 430, a second right-side pigtail 433, a second left-side pigtail 436 ... an Nth optical fiber ring to be tested 431, an Nth right-side pigtail 434, an Nth left-side pigtail 437, a first reflecting device 438, a second reflecting device 439 ... an Nth reflecting device 440. Light is controlled by the optical switch 410 to flow through a certain optical fiber ring to obtain its scattering spectrum.

[0029] (1) The optical switch 410 is a 1×N switch, including 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 optical switch is used in one arm of the interferometer to effectively reduce the influence of the optical switch reflection.

[0030] (2) The optical switch input arm 402 is connected to the left lower arm 307 of the third coupler through the twelfth flange 401 .

[0031] (3) The second circulator A port 406 is connected to the optical switch output first port 404 through the thirteenth flange 405 .

[0032] (4) The second circulator B port 408 is connected to the first right pigtail 432 via the fourteenth flange 409 .

[0033] (5) The second circulator C port 415 is connected to the first lower arm 328 of the fifth coupler through the fifteenth flange 407 .

[0034] (6) The third circulator A port 413 is connected to the optical switch output second port 411 through the sixteenth flange 412 .

[0035] (7) The third circulator B port 419 is connected to the second right pigtail 433 via the seventeenth flange 420 .

[0036] (8) The third circulator C port 417 is connected to the fifth coupler second lower arm 328 via the eighteenth flange 416 .

[0037] (9) The Nth circulator A port 423 is connected to the optical switch output Nth port 421 through the nineteenth flange 422 .

[0038] (10) The Nth circulator B port 427 is connected to the Nth right-side pigtail 434 through the twentieth flange 428.

[0039] (11) The Nth circulator C port 426 is connected to the Nth lower arm 326 of the fifth coupler through the twenty-first flange 425.

[0040] (12) The end of the first left pigtail 435 is cut flat to form a first reflective device 438.

[0041] (13) The end of the second left pigtail 436 is cut flat to form a second reflective device 439.

[0042] (14) The end of the Nth left pigtail 437 is cut flat to form the Nth reflector 440.

[0043] (15) The twenty-ninth optical fiber 402, the thirtieth optical fiber 404, the thirty-first optical fiber 411, the thirty-second optical fiber 421, the thirty-third optical fiber 406, the thirty-fourth optical fiber 413, the thirty-fifth optical fiber 423, the thirty-sixth optical fiber 408, the thirty-seventh optical fiber 419, the thirty-eighth optical fiber 427, the thirty-ninth optical fiber 415, the fortieth optical fiber 417, the forty-first optical fiber 426, the forty-second optical fiber 427, the optical fiber ring and the fiber pigtails 429 to 437 on both sides thereof are all polarization-maintaining optical fibers.

[0044] 4. A multi-parameter test device for multiple optical fiber sensitive rings according to claim 1, characterized in that the temperature control sensor module 5 comprises: a temperature box 501 and a temperature sensor 502. The temperature sensor 502 is placed in the temperature box 501. The first optical fiber ring to be tested 429, the second optical fiber ring to be tested 430 ... the Nth optical fiber ring to be tested 431 are all placed in the temperature box 501.

[0045] 5 . The multi-parameter testing device for multiple optical fiber sensitive rings according to claim 1 , wherein the control and data processing module 6 comprises: a control machine 601 , a data processing machine 602 , and a data acquisition card 603 .

[0046] (1) The first balanced photodetector 214 is connected to the data acquisition card 603 via the first electrical conductor 604 .

[0047] (2) The second balanced photodetector 321 is connected to the data acquisition card 603 via the second electrical conductor 605 .

[0048] (3) The third balanced photodetector 325 is connected to the data acquisition card 603 via the third electrical conductor 606 .

[0049] (4) The data acquisition card 603 is connected to the data processing machine 602 via a fourth electrical conductor 607.

[0050] (5) The control machine 601 is connected to the data acquisition card 603 via the fifth electrical conductor 608 .

[0051] (6) The control machine 601 is connected to the temperature sensor 502 via the sixth electrical conductor 609 .

[0052] (7) The control machine 601 is connected to the temperature box 501 via the seventh electrical conductor 610 .

[0053] (8) The control machine 601 is connected to the optical switch 410 via the eighth electrical conductor 611 .

[0054] (9) The control machine 601 is connected to the TLS light source 101 via the ninth electrical conductor 612 .

[0055] The present invention provides a testing method for a multi-parameter testing device of a multi-branch optical fiber sensitive ring, which is characterized by:

[0056] (1) To ensure the stability of the optical fiber ring, a full-temperature environmental test is performed on the optical fiber ring.

[0057] (2) Connect the first optical fiber ring 429, the second optical fiber ring 430, ..., the Nth optical fiber ring 431 to the test system to complete the optical path connection.

[0058] (3) The control machine 601 controls the TLS light source 101, the data acquisition card 603, the temperature box 501, the temperature sensor 502 and the optical switch 410 to start synchronously to perform a system self-check.

[0059] (4) The optical fiber ring is placed in the temperature box 501, and the control machine 601 sets the temperature box working curve, the temperature range is set to T1~T2, and the temperature change rate is maintained at T3 / min.

[0060] (5) The temperature chamber 501 is started, and the timing is set to 0. The control machine 601 starts to record the time, and the time is increased by 1 every 1 minute.

[0061] (6) Define the initial timings of the first optical fiber ring 429, the second optical fiber ring 430, ..., the Nth optical fiber ring 431 as 2, 3, ..., N+1 respectively, and then determine the current timing.

[0062] (7) When the sequence is 2, the optical switch 410 switches 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 optical fiber ring 429.

[0063] (8) When the sequence is 3, the optical switch 410 switches to the second output port, and the control machine 601 triggers the TLS light source 101 and the data acquisition card 603 to test the second optical fiber ring 430.

[0064] (9) When the sequence is N+1, the optical switch 410 switches to the Nth output port, and the control machine 601 triggers the TLS light source 101 and the data acquisition card 603 to test the Nth optical fiber ring 431.

[0065] (10) Collect test data and upload it to the data processor 602.

[0066] (11) Compensate for phase noise and determine whether the intensity of the end reflection peak after compensation is consistent with that at normal temperature.

[0067] (12) If the intensities are consistent, the tests of the first optical fiber ring 429, the second optical fiber ring 430, ..., the Nth optical fiber ring 431 are completed, and the temperature sensor data of the corresponding time sequence is recorded.

[0068] (13) If the intensity is inconsistent, perform phase noise compensation again to ensure that the intensity of the end reflection peak after compensation is consistent with that at normal temperature.

[0069] (14) The initial timing of each fiber ring is tested every time it increases by N.

[0070] (15) Record the P and S test data and obtain the scattering spectrum signal after Fourier transformation.

[0071] (16) OFDR system strain demodulation.

[0072] (17) The fiber ring strain data is obtained by correcting the thermo-optical coefficient based on the temperature sensor data.

[0073] The purpose of the present invention is to provide a device and method for improving test efficiency, measuring multiple parameters in multiple optical fiber rings in one rapid temperature cycle, and constructing an optical frequency domain test system for multi-parameter testing and performance evaluation of optical fiber rings and measuring the influence of rapid temperature changes on relative thermal strain in distributed optical fiber sensing systems.

[0074] The OFDR-based measurement device proposed in the present invention is shown in the attached figure. Figure 1 As shown, its characteristics are:

[0075] 1. It is composed of a TLS light source 101, a 45° polarizer 202, a first coupler 204, a first circulator 207, a second coupler 209, a first Faraday rotator 212, a second Faraday rotator 213, a first balanced photodetector 214, a third coupler 302, a fifth circulator 801, 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 device under test 802.

[0076] 2. The TLS light source 101 provides input light through the 45° polarizer 202 and the first coupler 204. 1% of the output light enters the first circulator 207 through the first connecting optical fiber 803, and enters the second coupler 209 through the B port of the first circulator and the second connecting optical fiber 804. The remaining 99% of the output light enters the third coupler 302 through the third connecting optical fiber 805.

[0077] 3. 50% of the light entering the second coupler 209 passes through the fourth connecting optical fiber 806 and is reflected by the first Faraday rotator 212 to form the first reflected light 807, and the other 50% passes through the delay optical fiber 808 and is reflected by the second Faraday rotator 213 to form the second reflected light 809. The first reflected light 807 and the second reflected light 809 generate beat frequency interference at the second coupler 209. A part of the beat frequency interference signal is sequentially input into the first balanced photodetector 214 through the second connecting optical fiber 804, the first circulator B port, the first circulator C port, and the fifth connecting optical fiber 810, and another part of the beat frequency interference signal is also input into the first balanced photodetector 214 through the sixth connecting optical fiber 811, and the two parts of the beat frequency interference signal are differentially detected.

[0078] 4. 1% of the light entering the third coupler 302 enters the fourth coupler 306 through the seventh connecting optical fiber 812, and the other 99% passes through the eighth connecting optical fiber 813 and the fifth circulator 801, and enters the device under test 802 from the fifth circulator A port, the fifth circulator B port and the ninth connecting optical fiber 814 in sequence. The third reflected signal 815 formed by reflection is also input into the fourth coupler 306 through the ninth connecting optical fiber 814, the fifth circulator B port, the fifth circulator C port and the tenth connecting optical fiber 816 to generate a beat frequency interference signal.

[0079] 5. 50% of the beat frequency interference signal generated at the fourth coupler 306 enters the first polarization-maintaining beam splitter 315 through the eleventh connecting optical fiber 817 , and the other 50% enters the second polarization-maintaining beam splitter 319 through the twelfth connecting optical fiber 818 .

[0080] 6. A portion of the light entering the first polarization-maintaining beam splitter 315 is input to the second balanced photodetector 321 via the thirteenth connecting optical fiber 819 , and another portion is input to the third balanced photodetector 325 via the fourteenth connecting optical fiber 820 .

[0081] 7. A portion of the light entering the second polarization-maintaining beam splitter 319 is input into the second balanced photodetector 321 via the fifteenth connecting optical fiber 821 , and another portion is input into the third balanced photodetector 325 via the sixteenth connecting optical fiber 822 .

[0082] The flowchart of the fiber ring temperature and strain testing method proposed by the present invention is shown in the attached figure. Figure 2 As shown, its characteristics are:

[0083] Step 701 is a full-temperature environment test of the optical fiber ring. The temperature environment commonly used by the optical fiber ring system is set to test the full-temperature performance of the optical fiber ring.

[0084] Step 702 is to connect the first optical fiber ring, the second optical fiber ring, ... the Nth optical fiber ring to the test system to complete the optical path connection.

[0085] Step 703 is to use the control machine to control the light source, data acquisition card, temperature box, temperature sensor and optical switch to start synchronously for system self-check.

[0086] Step 704 is to place the optical fiber ring in a temperature box, and the control machine sets the temperature box working curve, the temperature range is T1~T2, and the temperature rate is maintained at T3 / min.

[0087] Step 705 is to start the incubator, set the timing to 0, and the controller starts to record the time, adding 1 to the recording timing every 1 minute.

[0088] Step 706 is to define the initial timings of the first optical fiber ring, the second optical fiber ring, ... the Nth optical fiber ring as 2, 3, ... N+1 respectively, and start determining the timing.

[0089] From step 706, if the timing reaches 2, step 707 is executed: the optical switch is switched to the first port, and the control machine triggers the light source and the acquisition card, thereby testing the first optical fiber ring.

[0090] From step 706, if the timing reaches 3, step 708 is executed: the optical switch is switched to the second port, and the control machine triggers the light source and the acquisition card, thereby testing the second optical fiber ring.

[0091] From step 706, if the timing reaches N+1, step 709 is executed: the optical switch is switched to the Nth port, and the control machine triggers the light source and the acquisition card, thereby testing the Nth optical fiber ring.

[0092] Step 710 is to upload the test data collected by the data acquisition card to the data processing machine.

[0093] Step 711 is to compensate for phase noise and determine whether the intensity of the terminal reflection peak after compensation is consistent with that at normal temperature.

[0094] From step 711, if the intensity of the end reflection peak after compensation is consistent with the normal temperature, step 712 is executed: completing the test of the first optical fiber ring, the second optical fiber ring, ... the Nth optical fiber ring, and recording the temperature sensor data of the corresponding time sequence.

[0095] From step 711, if the intensity of the terminal reflection peak after compensation is inconsistent with the normal temperature, step 713 is executed: re-performing phase noise compensation.

[0096] Step 714 is to perform a test every time the initial timing of each optical fiber ring increases by N.

[0097] Step 715 is to record the test results of P and S at different temperatures, and obtain the scattering spectrum signal after Fourier transformation.

[0098] Step 716 is strain demodulation of the OFDR system. The reference signal and the test signal are cross-correlated by a demodulation algorithm to obtain the Rayleigh dispersion frequency shift of the optical fiber ring under temperature variation.

[0099] Step 717 is to correct the influence of the thermo-optic coefficient according to the temperature sensor data, thereby obtaining the optical fiber ring strain data.

[0100] The present invention proposes a multi-parameter testing device and method for multiple optical fiber sensitive rings. The basic principle of the device and method is the working principle of an optical frequency domain reflectometer. The OFDR system formed by an interferometer is used to demodulate the internal reflection signal of the optical fiber ring to obtain the influence of temperature and strain on the frequency shift of the optical fiber ring.

[0101] Device test principle:

[0102] The OFDR system built can realize independent strain and temperature testing. Based on the P and S signals, the relationship between the frequency shift and temperature and strain obtained by the test is as follows:

[0103]

[0104] Where: is the gauge factor of the cross-correlation frequency shift, is the temperature coefficient of the cross-correlation frequency shift.

[0105] It can be seen that the OFDR test results include both strain and temperature. The frequency shift obtained by OFDR testing includes the influence of both temperature and strain. The obtained spectral offset is converted by temperature and gauge coefficient to obtain the corresponding temperature and strain values.

[0106] Compared with the prior art, the advantages of the present invention are:

[0107] 1. The present invention effectively reduces the influence of optical switch reflection by using an optical switch in one arm of the interferometer.

[0108] 2. The test device proposed in the present invention can realize distributed high-precision measurement of multiple parameters (temperature and strain) of a long-distance optical fiber sensitive ring under rapid temperature changes.

[0109] 3. The present invention can test the multi-parameter performance of multiple optical fiber rings under temperature changes at the same time by designing a system timing control method.

[0110] 4. The present invention has a simple structure, high test accuracy, and is resistant to environmental interference, which effectively improves the test efficiency and can be widely used in high-precision measurement and analysis of multi-parameter performance of optical devices such as polarization-maintaining optical fibers, optical fiber rings, and hydrophones. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] Figure 1 This is the test principle diagram of Optical Frequency Domain Reflectometry (OFDR);

[0112] Figure 2 is a flow chart of the fiber optic ring temperature and strain test method;

[0113] Figure 3 It is the structure diagram of the optical fiber ring to be tested;

[0114] Figure 4 It is a flow chart of the full temperature test method;

[0115] Figure 5 It is a diagram of a multi-parameter test device for multiple optical fiber sensitive rings;

[0116] Figure 6 It is a schematic diagram of the optical fiber ring strain test results. DETAILED DESCRIPTION

[0117] In order to clearly illustrate the device and method for testing multiple parameters in an optical fiber ring of the present invention, the present invention is further described in conjunction with embodiments and drawings, but this should not limit the protection scope of the present invention.

[0118] Figure 3 This is the structure of the optical fiber ring to be tested of the present invention. Its characteristics are:

[0119] The optical fiber ring structure to be tested is composed of a first optical fiber ring to be tested 429, a first reflecting device 438, a second optical fiber ring to be tested 430, a second reflecting device 439 ... an Nth optical fiber ring to be tested 431, and an Nth reflecting device 440. The first optical fiber ring to be tested 429 includes a first right-side pigtail 432 and a first left-side pigtail 435; the second optical fiber ring to be tested 430 includes a second right-side pigtail 433 and a second left-side pigtail 436; the Nth optical fiber ring to be tested 431 includes an Nth right-side pigtail 434 and an Nth left-side pigtail 437;

[0120] When any of the fiber rings is connected to the optical path of the OFDR test system, the light passes through the right pigtail, the fiber ring to be tested, the left pigtail and the reflector, and is strongly reflected. The strongly reflected light passes through the left pigtail, the fiber ring to be tested, the right pigtail in turn, and returns to the optical path of the OFDR test system.

[0121] Combination Figure 4 , the full temperature test method is as follows:

[0122] Step 718 is to set the temperature range of the high and low temperature box to T1~T2, and the temperature change rate to 1°C / min.

[0123] Step 719 is to place the optical fiber ring inside the temperature box to keep the sensitive ring heated on all four sides.

[0124] Step 720 is to keep the optical fiber ring at temperature T3 for 30 minutes.

[0125] Step 721 is to cool the temperature of the incubator from T3 to T1 at a rate of 1°C / min.

[0126] Step 722 is to keep the optical fiber ring at temperature T1 for 60 minutes.

[0127] Step 723 is to increase the temperature of the incubator from T1 to T2 at a rate of 1°C / min.

[0128] Step 724 is to keep the optical fiber ring at temperature T2 for 60 minutes.

[0129] Step 725 is that the OFDR system performs a test every 5 minutes.

[0130] Figure 5 The invention is a multi-parameter test device for multiple optical fiber sensitive rings, including a TLS light source module 1, an auxiliary interferometer module 2, a main interferometer module 3, a module to be tested 4, a temperature control sensor module 5 and a control and data processing module 6. The structure of the module to be tested 4 is similar to Figure 3 The N optical fiber rings to be tested have the same structure.

[0131] Combination Figure 5One implementation of the present invention is: setting the sweep range of the TLS light source 101 to 10nm~160nm and the sweep speed to 10nm / s, and 1% of the swept light emitted by the first coupler 204 enters the auxiliary interferometer module 2 and 99% enters the main interferometer module 3.

[0132] 1% of the light entering the main interferometer module 3 passes through the third coupler left upper arm 303 and the fourth coupler right upper arm 305 and enters the fourth coupler 306 , and the other 99% passes through the third coupler left lower arm 307 and enters the optical switch 410 .

[0133] The 1% light passing 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 passing through the third coupler left lower arm 307 is input into the optical switch 410 and a gyroscope optical path as a test signal. The two signals are received by the data acquisition card 603 with a sampling frequency of 180MHz after the beat frequency interference occurs at the fourth coupler 306.

[0134] The controller 601 performs opening and closing operations on the 1×N output ports of the optical switch 410.

[0135] If the current time sequence is a value in an arithmetic progression with a first term of 2 and a tolerance of N, the optical switch switches to the first port 404, and the control machine 601 triggers the TLS light source 101 and the data acquisition card 603 to test the first optical fiber ring 429;

[0136] If the current time sequence is a value in an arithmetic progression with a first term of 3 and a tolerance of N, the optical switch switches to the second port 411, and the control machine 601 triggers the TLS light source 101 and the data acquisition card 603 to test the second optical fiber ring 430;

[0137] If the current time sequence is a value in an arithmetic progression with the first term being N+1 and the tolerance being N, the optical switch switches to the Nth port 421 , and the control machine 601 triggers the TLS light source 101 and the data acquisition card 603 to test the Nth optical fiber ring 431 .

[0138] When any of the fiber rings is connected to the optical path of the OFDR test system, the light passes through the right pigtail, the fiber ring to be tested, the left pigtail and the reflector, and is strongly reflected. The strong reflected light passes through the left pigtail, the fiber ring to be tested, and the right pigtail in turn, and returns to the optical path of the OFDR test system with the scattering information of the fiber ring.

[0139] Collect test data. Perform phase noise compensation on the data uploaded to the data processor to determine whether the reflection peak intensity at the end after compensation is consistent with that at normal temperature. If consistent, complete the test of the fiber ring and record the temperature sensor data of the corresponding time sequence. If inconsistent, perform phase noise compensation again until the reflection peak intensity at the end after compensation is consistent with that at normal temperature.

[0140] Record the P and S test data, and get the scattering spectrum signal after Fourier transformation.

[0141] OFDR system strain demodulation. The reference signal and the test signal are cross-correlated by the demodulation algorithm to obtain the Rayleigh dispersion frequency shift of the fiber ring under temperature variation.

[0142] The influence of the thermo-optical coefficient is corrected according to the temperature sensor data, thereby obtaining the fiber ring strain data. The fiber ring strain test results are as follows: Figure 6 As shown in Figure 2, the spatial resolution of this OFDR-based fiber ring multi-parameter test device is 5 cm, and the strain resolution is ±1 .

Claims

1. A multi-parameter test device for multiple optical fiber sensitive rings, characterized by: The device comprises a TLS light source module (1), an auxiliary interferometer module (2), a main interferometer module (3), a module to be tested (4), a temperature control sensor module (5) and a control and data processing module (6). The control and data processing module (6) controls the TLS light source (101), a data acquisition card (603), a temperature box (501), a temperature sensor (502) and an optical switch (410). The TLS light source module (1) injects a light beam into a first coupler (204), a 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). The module to be tested (4) is connected to the main interferometer module (3) and placed in the temperature control sensor module (5), and the auxiliary interference signal and the main interference signal are fed into the data acquisition card (603), and finally the scattering and reflection characteristics of the device to be tested are obtained.

2. A multi-parameter test device for multiple optical fiber sensitive rings according to claim 1, characterized in that The auxiliary interferometer module (2) comprises: a 45° polarizer (202), a first coupler (204), a first circulator (207), a second coupler (209), a first Faraday rotation mirror (212), a second Faraday rotation mirror (213), and a first balanced photodetector (214). Light undergoes beat frequency interference in the second coupler (209). (1) A 45° polarizer (202) is connected to a TLS light source (101) via a first flange (201). (2) The left arm (218) of the first coupler is connected to the 45° polarizer (202) via the second flange (203). (3) The A port (221) of the first circulator is connected to the right lower arm (220) of the first coupler via the fourth flange (206). (4) The right upper arm (224) of the second coupler is connected to the B port (222) of the first circulator via the fifth flange (208). (5) The right lower arm (215) of the second coupler and the C port (223) of the first circulator are respectively connected to the first balanced photodetector (214). (6) The first Faraday rotation mirror (212) is connected to the left upper arm (225) of the second coupler via the sixth flange (210). (7) The second Faraday rotation mirror (213) is connected to the left lower arm (226) of the second coupler via the seventh flange (211). (8) The first optical fiber (216), the second optical fiber (217), the third optical fiber (218), the fourth optical fiber (219), and the fifth optical fiber (220) are all polarization-maintaining optical fibers. (9) The sixth optical fiber (221), the seventh optical fiber (222), the eighth optical fiber (223), the ninth optical fiber (224), the tenth optical fiber (215), the eleventh optical fiber (225), and the delay optical fiber (226) are all single-mode optical fibers.

3. A multi-parameter test device for multiple optical fiber sensitive rings according to claim 1, characterized in that 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 in the fourth coupler (306). (1) The third coupler right arm (301) is connected to the first coupler right upper arm (219) via the third flange (205). (2) The fourth coupler right upper arm (305) is connected to the third coupler left upper arm (303) via the eighth flange (304). (3) The right lower arm (311) of the fourth coupler is connected to the upper arm (309) of the fifth coupler via the ninth flange (310). (4) The right arm (314) of the first polarization-maintaining beam splitter is connected to the left upper arm (312) of the fourth coupler via the tenth flange (313). (5) The right arm (318) of the second polarization-maintaining beam splitter is connected to the left lower arm (316) of the fourth coupler through the eleventh flange (317). (6) The second balanced photodetector (321) is respectively connected to the left upper arm (320) of the first polarization-maintaining beam splitter and the left upper arm (323) of the second polarization-maintaining beam splitter. (7) The third balanced photodetector (325) is connected to the left lower arm (322) of the first polarization-maintaining beam splitter and the left lower arm (324) of the second polarization-maintaining beam splitter respectively. (8) The twelfth optical fiber (301), the thirteenth optical fiber (303), the fourteenth optical fiber (307), the fifteenth optical fiber (305), the sixteenth optical fiber (311), the seventeenth optical fiber (312), the eighteenth optical fiber (316), the nineteenth optical fiber (314), the twentieth optical fiber (318), the twenty-first optical fiber (320), the twenty-second optical fiber (322), the twenty-third optical fiber (323), the twenty-fourth optical fiber (324), the twenty-fifth optical fiber (326), the twenty-sixth optical fiber (327), the twenty-seventh optical fiber (328), and the twenty-eighth optical fiber (309) are all polarization-maintaining optical fibers.

4. A multi-parameter test device for multiple optical fiber sensitive rings according to claim 1, characterized in that The module to be tested (4) comprises: an optical switch (410), a second circulator (416), a third circulator (418) ... an N+1th circulator (424), a first optical fiber ring to be tested (429), a first right-side pigtail (432), a first left-side pigtail (435), a second optical fiber ring to be tested (430), a second right-side pigtail (433), a second left-side pigtail (436) ... an Nth optical fiber ring to be tested (431), an Nth right-side pigtail (434), an Nth left-side pigtail (437), a first reflecting device (438), a second reflecting device (439) ... an Nth reflecting device (440). Light is controlled by the optical switch (410) to flow through a certain optical fiber ring to obtain its scattering spectrum. (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 optical switch is used in one arm of the interferometer to effectively reduce the influence of the optical switch reflection. (2) The optical switch input arm (402) is connected to the left lower arm (307) of the third coupler via the twelfth flange (401). (3) The second circulator A port (406) is connected to the optical switch output first port (404) through the thirteenth flange (405). (4) The second circulator B port (408) is connected to the first right pigtail (432) via the fourteenth flange (409). (5) The second circulator C port (415) is connected to the first lower arm (328) of the fifth coupler via the fifteenth flange (407). (6) The third circulator A port (413) is connected to the optical switch output second port (411) through the sixteenth flange (412). (7) The third circulator B port (419) is connected to the second right pigtail (433) via the seventeenth flange (420). (8) The C port (417) of the third circulator is connected to the second lower arm (328) of the fifth coupler through the eighteenth flange (416). (9) The Nth circulator A port (423) is connected to the optical switch output Nth port (421) through the nineteenth flange (422). (10) The Nth circulator B port (427) is connected to the Nth right-hand pigtail (434) via the twentieth flange (428). (11) The C port (426) of the Nth circulator is connected to the Nth lower arm (326) of the fifth coupler via the twenty-first flange (425). (12) The end of the first left pigtail (435) is cut flat to form a first reflective device (438). (13) The end of the second left pigtail (436) is cut flat to form a second reflective device (439). (14) The end of the Nth left pigtail (437) is cut flat to form the Nth reflector (440). (15) The twenty-ninth optical fiber (402), the thirtieth optical fiber (404), the thirty-first optical fiber (411), the thirty-second optical fiber (421), the thirty-third optical fiber (406), the thirty-fourth optical fiber (413), the thirty-fifth optical fiber (423), the thirty-sixth optical fiber (408), the thirty-seventh optical fiber (419), the thirty-eighth optical fiber (427), the thirty-ninth optical fiber (415), the fortieth optical fiber (417), the forty-first optical fiber (426), the forty-second optical fiber (427), the optical fiber ring and the pigtails on both sides thereof (429-437) are all polarization-maintaining optical fibers.

5. A multi-parameter test device for multiple optical fiber sensitive rings according to claim 1, characterized in that The temperature control sensing module (5) comprises: a temperature box (501) and a temperature sensor (502). The temperature sensor (502) is placed in the temperature box (501). The first optical fiber ring to be tested (429), the second optical fiber ring to be tested (430) ... the Nth optical fiber ring to be tested (431) are all placed in the temperature box (501).

6. A multi-parameter test device for multiple optical fiber sensitive rings 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 to the data acquisition card (603) via a first electrical conductor (604). (2) The second balanced photoelectric detector (321) is connected to the data acquisition card (603) via a second electrical conductor (605). (3) The third balanced photoelectric detector (325) is connected to the data acquisition card (603) via a third electrical conductor (606). (4) The data acquisition card (603) is connected to the data processing machine (602) via a fourth electrical conductor (607). (5) The control machine (601) is connected to the data acquisition card (603) via a fifth electrical conductor (608). (6) The control machine (601) is connected to the temperature sensor (502) via a sixth electrical conductor (609). (7) The control machine (601) is connected to the temperature box (501) via a seventh electrical conductor (610). (8) The control machine (601) is connected to the optical switch (410) via an eighth electrical conductor (611). (9) The control machine (601) is connected to the TLS light source (101) via a ninth electrical conductor (612).

7. The testing method of a multi-parameter testing device for a multi-branch optical fiber sensitive ring according to claim 1, characterized in that: (1) To ensure the stability of the optical fiber ring, a full-temperature environmental test is performed on the optical fiber ring. (2) Connect the first optical fiber ring (429), the second optical fiber ring (430), ... the Nth optical fiber ring (431) to the test system to complete the optical path connection. (3) The control machine (601) controls the TLS light source (101), the data acquisition card (603), the temperature box (501), the temperature sensor (502) and the optical switch (410) to start synchronously to perform a system self-check. (4) The optical fiber ring is placed in a temperature box (501), and the control machine (601) sets the temperature box working curve, sets the temperature range to T1~T2, and maintains the temperature change rate at T3 / min. (5) The temperature box (501) is started, and the timing is set to 0. The control machine (601) starts to record the time, and the recording time is increased by 1 every 1 minute. (6) Define the initial timings of the first optical fiber ring (429), the second optical fiber ring (430) ... the Nth optical fiber ring (431) as 2, 3 ... N+1 respectively, and then determine the current timing. (7) When the sequence is 2, the optical switch (410) switches 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 optical fiber ring (429). (8) When the sequence is 3, the optical switch (410) switches to the second output port, and the control machine (601) triggers the TLS light source (101) and the data acquisition card (603) to test the second optical fiber ring (430). (9) When the sequence is N+1, the optical switch (410) switches to the Nth output port, and the control machine (601) triggers the TLS light source (101) and the data acquisition card (603) to test the Nth optical fiber ring (431). (10) Collect test data and upload it to the data processing machine (602). (11) Compensate for phase noise and determine whether the intensity of the end reflection peak after compensation is consistent with that at normal temperature. (12) If the intensities are consistent, the test of the first optical fiber ring (429), the second optical fiber ring (430) ... the Nth optical fiber ring (431) is completed, and the temperature sensor data of the corresponding time sequence is recorded. (13) If the intensity is inconsistent, perform phase noise compensation again to ensure that the intensity of the end reflection peak after compensation is consistent with that at normal temperature. (14) The initial timing of each fiber ring is tested every time it increases by N. (15) Record the P and S test data and obtain the scattering spectrum signal after Fourier transformation. (16) OFDR system strain demodulation. (17) The fiber ring strain data is obtained by correcting the thermo-optical coefficient based on the temperature sensor data.

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