Device for simultaneously measuring temperature, strain and crosstalk of optical fiber sensitive ring

Abstract

The invention provides a device for simultaneously measuring temperature, strain and crosstalk of an optical fiber sensitive ring. The device comprises an optical path switching module, a Brillouin optical time domain analyzer and an optical coherence domain polarization measuring instrument. Based on a Brillouin optical time domain analyzer and an optical coherence domain polarization measuring instrument, an optical path switching module is used for merging and separating optical signals during testing of the two instruments, and simultaneous measurement of the temperature, the strain and the crosstalk of the optical fiber sensitive ring can be achieved on the premise that the testing result is not affected. According to the device, the influence of external factors can be eliminated, the repeated welding of an optical path is avoided, the test process is simplified, and the test efficiency is improved. The number of used optical devices is small, the structure is simple, the building cost is low, and existing instruments do not need to be transformed. The device provided by the invention provides support for multi-parameter comprehensive analysis of the optical fiber sensitive ring, can be widely applied to multi-parameter measurement of various polarization-maintaining optical fiber sensitive rings, and is of great significance to test, evaluation and process optimization of the optical fiber sensitive ring.

Description

Technical Field

[0001] The invention belongs to the technical field of optical device measurement, and in particular relates to a device for simultaneously measuring temperature, strain and crosstalk of an optical fiber sensitive ring. Background Art

[0002] Fiber optic gyroscope is a rotation angular velocity and angular acceleration sensor based on Sagnac effect. It is widely used in ship navigation and missile guidance due to its advantages of light weight, small size, high precision and low cost. Fiber optic sensitive ring and Y waveguide are the core components of fiber optic gyroscope. Fiber optic sensitive ring is made of hundreds or even thousands of meters of polarization-maintaining optical fiber according to certain methods and processes. It is mainly used to sense external motion and is equivalent to the "brain" of fiber optic gyroscope. Y waveguide is a waveguide chip etched by photolithography technology and is the "heart" of the information transfer hub of fiber optic gyroscope. It can be seen from the Sagnac effect that if the fiber optic gyroscope is to have a higher sensing accuracy, the fiber optic sensitive ring must have good reciprocity and symmetry while having low distributed polarization crosstalk; however, in the process of fiber optic sensitive ring manufacturing, it is inevitably affected by factors such as torsion, pressure, friction, and gluing, resulting in residual stress, winding asymmetry, gap bubbles and other problems inside the finished fiber optic sensitive ring. These problems will cause serious polarization coupling inside it and reduce the reliability of the fiber optic sensitive ring. Therefore, in order to eliminate the above problems and improve the reciprocity, symmetry, polarization characteristics and reliability of the fiber optic sensitive loop, it is very important to conduct a comprehensive test and evaluation of the fiber optic sensitive loop, which is of great significance for the improvement of the loop winding process and the performance of the fiber optic gyroscope.

[0003] For the testing and evaluation of optical fiber sensitive loops, important research results have been achieved in many aspects, and methods and devices for testing and evaluating optical fiber sensitive loops from various angles have been proposed. Currently, there are several ideas for evaluating the reciprocity, symmetry, polarization characteristics and reliability of optical fiber sensitive loops:

[0004] The test is conducted from the perspective of stress distribution. The device is used to test the distributed stress of the optical fiber sensitive ring. According to the size and concentration of stress in the ring, the winding quality of the optical fiber sensitive ring is evaluated. In 2014, Yang Dongkun and others from the 618th Institute of China Aviation Industry disclosed a method for evaluating and compensating the reciprocal symmetry of an optical fiber ring (CN201410392975.3). The invention uses enhanced Brillouin backreflection detection technology to obtain the internal stress state distribution data of the optical fiber sensitive ring, and uses the data to establish a symmetry model and analyze the reciprocal symmetry of the optical fiber ring to be tested.

[0005] From the perspective of temperature characteristics, the device is used to test the distributed temperature of the optical fiber sensitive ring. According to the working temperature, temperature diffusion speed and uniformity, the symmetry and gluing uniformity of the optical fiber sensitive ring structure are evaluated. In 2008, Yao Xiaotian and others from Suzhou Guanghuan Technology Co., Ltd. disclosed a method and device for measuring the quality of optical fiber rings for optical fiber gyroscopes (CN200810119075.6). By applying temperature excitation to the optical fiber ring and measuring the temperature characteristics of the transient ring, the temperature symmetry of the optical fiber ring is measured in combination with a three-dimensional model. In 2016, Chen Xingfan and others from Zhejiang University disclosed a method and device for measuring the temperature variation characteristics of the optical fiber ring of an optical fiber gyroscope (CN201610933044.9). By placing the optical fiber ring part of the optical fiber gyroscope on a turntable in a temperature-controlled environment, applying a specific angular velocity and temperature, and analyzing the signal output by the optical fiber gyroscope, the temperature variation characteristics of the optical fiber ring are obtained, thereby realizing the test and evaluation of the temperature performance of the optical fiber sensitive ring structure.

[0006] From the perspective of polarization characteristics, the device is used to test the distributed polarization crosstalk of the fiber sensitive loop in the forward and reverse directions. According to the distribution of polarization crosstalk in the loop, the polarization crosstalk level, extinction ratio and symmetry of the fiber sensitive loop are evaluated. In 2011, Yang Jun et al. from Harbin Engineering University disclosed a device and method for improving the measurement accuracy and symmetry of polarization coupling of polarization-maintaining fiber (CN201110118450.7). The invention is based on the optical coherence domain polarization meter OCDP (Optical Coherence Domain Polarization). By adding an optical signal reversing mechanism in the test optical path, the bidirectional measurement of the distributed polarization crosstalk of the fiber sensitive loop is realized; according to the test results, the polarization characteristics and symmetry of the fiber sensitive loop can be evaluated. In 2012, Yang Dewei and others from Beijing University of Aeronautics and Astronautics disclosed a method for estimating polarization crosstalk and evaluating symmetry of optical fiber ring (CN201210359805.6), using coherent domain polarization detection technology to obtain polarization coupling intensity distribution data, and then using wavelength scanning method to obtain the birefringence dispersion coefficient of the optical fiber, and analyzing the symmetry of the optical fiber ring by calculating the polarization crosstalk on the left and right sides of the midpoint of the optical fiber sensitive ring. In 2017, Wu Chongqing and others from Beijing Jiaotong University disclosed a system and method for evaluating polarization mode coupling characteristics of optical fiber sensitive ring (CN108287056B), which is based on polarization optical time domain reflectometer, uses polarization analyzer to measure backscattered light, obtains the Stokes vector of reflected light at each point of the optical fiber sensitive ring, and solves the distributed polarization coupling of the optical fiber sensitive ring. In the same year, Yang Jun and others from Harbin Engineering University disclosed a common optical path fiber gyroscope ring forward and reverse simultaneous measurement device (CN201710050099.X). The invention adopts a common optical path structure and can realize the measurement of forward and reverse signals with only one set of demodulation interferometer. Compared with the previous fiber optic sensitive ring bidirectional measurement method, it greatly simplifies the complexity of the measurement device.

[0007] The test is conducted from the perspective of imaging scanning, using the perspective of optical imaging to image the surface or internal conditions of the fiber sensitive ring, evaluate the uniformity of the fiber sensitive ring, and eliminate defects. In 2012, Yao Xiaotian and others from Suzhou Guanghuan Technology Co., Ltd. disclosed a fiber ring quality detection method and device based on optical coherence tomography technology (CN201210381902.5). The invention is based on optical coherence tomography technology, using the probe of the scanning system to perform a one-dimensional scan along the axis of the fiber sensitive ring, and establishing a three-dimensional image based on the scanning results. From the reconstructed image, it is determined whether there are defects on the surface and below the surface of the fiber sensitive ring, and the defects are located.

[0008] In the above methods, the optical fiber sensitive ring is tested and evaluated from a single perspective, and the information reflected is very one-sided. For example, if the optical fiber sensitive ring is evaluated from the perspective of stress distribution or polarization characteristics, although the stress concentration point or polarization crosstalk point in the optical fiber sensitive ring can be directly reflected, the stress affects the performance of the optical fiber gyroscope by generating polarization crosstalk. Polarization crosstalk is not only related to the radial stress of the optical fiber, but also to the direction of radial stress application. This means that relatively high stress does not necessarily produce large polarization crosstalk, and relatively small stress does not necessarily have no effect on the optical fiber sensitive ring. Therefore, it is unreliable to evaluate the optical fiber sensitive ring only from the perspective of a single parameter. If the optical fiber sensitive ring is to be accurately evaluated and the winding process is to be improved, a multi-parameter test method for the optical fiber sensitive ring is essential.

[0009] In view of the above problems, the present invention proposes a new simultaneous measurement device for the temperature, strain and crosstalk of an optical fiber sensitive ring. The device is based on the existing Brillouin optical time domain analyzer and optical coherence domain polarization measuring instrument, and uses an optical path adapter module to merge and separate the optical signals of the above two instruments during testing, so as to achieve simultaneous measurement of the temperature, strain and crosstalk of the optical fiber sensitive ring without affecting the test results. The device of the present invention provides support for the comprehensive analysis of multiple parameters of the optical fiber sensitive ring, obtains the three physical parameters of the optical fiber sensitive ring through one measurement, eliminates the influence of external factors on the existing test methods, avoids repeated welding of the optical path during the test, simplifies the test process and improves the test efficiency. The optical path adapter part adopts a modular design, and there is no need to modify the internal optical path of the existing equipment; the module uses a small number of optical devices, a simple structure and a low construction cost. The proposed device can be widely used in the multi-parameter measurement of various polarization-maintaining optical fiber sensitive rings, which is of great significance to the testing, evaluation and process optimization of optical fiber sensitive rings. Summary of the invention

[0010] The purpose of the present invention is to provide a device for simultaneously measuring the temperature, strain and crosstalk of an optical fiber sensitive ring, so as to realize the simultaneous measurement of the distributed temperature, strain and crosstalk of the optical fiber sensitive ring, and to evaluate important parameters such as the polarization characteristics, internal stress distribution and winding symmetry of the optical fiber sensitive ring.

[0011] The present invention provides a device for simultaneously measuring temperature, strain and crosstalk of an optical fiber sensitive ring, and the device comprises: an optical path switching module 11, a Brillouin optical time domain analyzer 13, and an optical coherence domain polarization measuring instrument 14.

[0012] The pump light, detection light and low-bias wide spectrum light output by the Brillouin optical time domain analyzer 13 and the optical coherence domain polarimeter 14 enter the optical fiber sensitive ring 12 through the optical path adapter module 11. At the same time, the signal light carrying the temperature, strain and crosstalk of the optical fiber sensitive ring 12 returns to the Brillouin optical time domain analyzer 13 and the optical coherence domain polarimeter 14 through the optical path adapter module 11 for demodulation. The optical path adapter module 11 couples and separates the optical signals of the two instruments to achieve simultaneous measurement of the temperature, strain and crosstalk of the optical fiber sensitive ring 12.

[0013] The Brillouin optical time domain analyzer 13 is connected to the optical path adapter module 11 in such a manner that the Brillouin optical time domain analyzer 13 is connected to the optical path adapter module 11 through the fourth port 104 of the optical path adapter module 11, and is connected to the optical path adapter module 11 through the fifth port 105 of the optical path adapter module 11, wherein the detection light output port of the Brillouin optical time domain analyzer 13 is connected to the fourth port 104;

[0014] The connection method between the optical coherence domain polarimeter 14 and the optical path adapter module 11 is that the optical coherence domain polarimeter 14 is connected to the optical path adapter module 11 through the third port 103 and the sixth port 106 of the optical path adapter module 11, wherein the low-bias wide-spectrum light output port of the optical coherence domain polarimeter 14 is connected to the third port 103.

[0015] According to claim 1, the optical path adapter module 11 is characterized in that: the optical path adapter module 11 is composed of a 0° optical fiber polarizer 111, a first optical fiber polarization beam splitter 112, a second optical fiber polarization beam splitter 114, a polarization-maintaining optical fiber coupler 113, a polarization-maintaining optical fiber circulator 115, and a 45° optical fiber analyzer 116.

[0016] The 0° optical fiber polarizer output end 111b of the 0° optical fiber polarizer 111 is connected to the polarization-maintaining optical fiber coupler 113, the first output end 113c of the first optical fiber polarization beam splitter is connected to the polarization-maintaining optical fiber coupler 113, the second output end 112c of the first optical fiber polarization beam splitter is connected to the second optical fiber polarization beam splitter 114, and the polarization-maintaining optical fiber coupler output end 113a is connected to the second optical fiber polarization beam splitter 114; the 45° optical fiber analyzer input end 116b is connected to the polarization-maintaining optical fiber circulator 115, and all the above connection points are connected by fusion splicing, and the fusion axis angle is 0°;

[0017] The optical path adapter module 11 includes 6 input and output ports, the first port 101 is connected to the second optical fiber polarization beam splitter 114, the second port 102 is connected to the polarization-maintaining optical fiber circulator 115, the third port 103 is connected to the 0° optical fiber polarizer 111, the fourth port 104 is connected to the first optical fiber polarization beam splitter 112, the fifth port 105 is connected to the corresponding polarization-maintaining optical fiber circulator 115, and the sixth port 106 is connected to the 45° optical fiber polarization analyzer 116 through the 45° optical fiber polarization analyzer output end 116a;

[0018] The first port 101 and the second port 102 are access ports for the optical fiber sensitive ring 12, the third port 103 is a low-bias wide-spectrum light input port, the fourth port 104 is a pump light, detection light and reflected light input / output port, the fifth port 105 is a pump light input port, and the sixth port 106 is a transmission light and coupling light output port; wherein, the fourth port 104 and the fifth port 105 are access ports for the Brillouin optical time domain analyzer 13, and the third port 103 and the sixth port 106 are access ports for the optical coherence domain polarimeter 14.

[0019] The optical path adapter module 11 is composed of 6 optical devices, which are characterized in that: the working axis of the 0° optical fiber polarizer 111 is the fast axis, the 0° optical fiber polarizer input end 111a is the single-mode input end, the 0° optical fiber polarizer output end 113b is the polarization-maintaining output end, the working axis of the 45° optical fiber analyzer 116 is aligned at 45° with the fast axis of the pigtail, in addition, the 45° optical fiber polarizer output end 116a is the single-mode output end, the 45° optical fiber analyzer input end 116b is the polarization-maintaining input end, the first optical fiber polarization beam splitter 112 and the second optical fiber polarization beam splitter 114 are three-port devices, and both are polarization-maintaining pigtail input / output, wherein the first output end 113c of the first optical fiber polarization beam splitter and the output end 113c of the polarization-maintaining optical fiber coupler are fast-axis output / input ends, and the second output end 112c of the first optical fiber polarization beam splitter is a slow-axis output / input end.

[0020] The polarization-maintaining fiber coupler 113 is a three-port device, and the splitting ratio between the 0° fiber polarizer output end 113b and the first output end 113c of the first polarization beam splitter is 50:50. At the same time, the polarization-maintaining fiber circulator 115 is a three-port device, and its optical transmission path is the first input end 115a of the polarization-maintaining circulator→the second input end 115b of the polarization-maintaining circulator→the input end 116b of the 45° fiber analyzer.

[0021] The specific steps of the simultaneous measurement scheme of temperature, strain and crosstalk of the optical fiber sensitive ring are as follows:

[0022] According to the optical path structure diagram, the optical path is constructed, and the optical fiber lengths of the 0° optical fiber polarizer input end 111a, the 0° optical fiber polarizer output end 113b, the first optical fiber polarization beam splitter input end 112a, the first optical fiber polarization beam splitter first output end 113c, the polarization-maintaining optical fiber coupler output end 113a, and the second optical fiber polarization beam splitter output end 114a, as well as the optical fiber lengths of the polarization-maintaining circulator first input end 115a, the polarization-maintaining circulator second input end 115b, and the 45° optical fiber analyzer input end 116b are determined, and recorded in sequence as: l 111a , l 113b , l 112a , l 113c , l 113a , l 114a , l 115a , l 115b , l 116b ;

[0023] Calculate the spatial optical path difference corresponding to the optical fiber length from the 0° optical fiber polarizer output end 113b, the first polarization beam splitter first output end 113c, the first polarization beam splitter second output end 112c to the second polarization beam splitter, the polarization-maintaining circulator first input end 115a, the polarization-maintaining circulator second input end 115b, and the 45° optical fiber analyzer input end 116b, and record them in sequence as: S 113b , S 113c , S 112c , S 115a , S 115b , S 116b , if the birefringence of the polarization-maintaining fiber is Δn, then the calculation method of the spatial optical path difference of a certain section of fiber is: the actual length of the fiber × birefringence Δn;

[0024] The two free ports of the optical fiber sensitive ring 12 are respectively fused with the first port 101 and the second port 102 of the optical path adapter module 11, and the axial angle of the optical fiber during fusion is 0°;

[0025] The detection light output port of the Brillouin optical time domain analyzer 13 is connected to the fourth port 104 of the optical path adapter module 11, and the other port is connected to the fifth port 105 of the optical path adapter module 11; the low-bias wide-spectrum light output port of the optical coherence domain polarization meter 14 is connected to the third port 103 of the optical path adapter module 11, and the other port is connected to the sixth port 106 of the optical path adapter module 11; the above connection methods all adopt flange connection;

[0026] Start the Brillouin optical time domain analyzer 13, set the measurement range and the sweep frequency range, ensure that the information of the optical fiber sensitive ring 12 can be fully measured, and pre-test the optical fiber sensitive ring 12; after the test is completed, read and record the Brillouin frequency shift of the optical fiber sensitive ring 12; if the Brillouin frequency shift parameters of the optical fiber sensitive ring 12 are known, this step can be skipped;

[0027] Start the Brillouin optical time domain analyzer 13 and the optical coherence domain polarimeter 14, adjust the Brillouin optical time domain analyzer 13 to the Brillouin dynamic grating mode, input the parameters such as the Brillouin frequency shift of the optical fiber sensitive ring 12, set a larger measurement range (sweep range) to ensure that the information of the optical fiber sensitive ring 12 can be fully obtained, and test the optical fiber sensitive ring at the same time; after the test is completed, save the data, and perform dispersion compensation and normalization on the distributed polarization crosstalk test results, and save the test data after dispersion compensation;

[0028] The information range of the optical fiber sensitive ring 12 is determined in the test result after polarization crosstalk dispersion compensation. The range is determined based on the polarization crosstalk peak corresponding to the fusion point between the first port 101 and the second port 102. The specific process is as follows: record the polarization crosstalk peak (S Max , ρ), according to the measured optical fiber length and its corresponding optical path difference, it can be known from the principle of white light interferometry that the polarization crosstalk peak optical path difference corresponding to the second port 102 in the test result is: S Path2 =S 116b +S 115c , the polarization crosstalk peak optical path difference corresponding to the first port 101 in the test result is: S Path1 =S Max -(S 113b + S 113a +S 114a ), the length of the optical fiber sensitive ring 12 is l Fiber =(S Path1 -S Path2 ) / Δn, information range (S Path2 ,S Path1 );

[0029] The information range of the optical fiber sensitive ring 12 is determined in the Brillouin domain test result. The range is realized based on the delay between the first port 101 and the second port 102. The specific process is as follows: record the maximum delay T in the test result. Max Assuming that the refractive index of the optical fiber is n, according to the Brillouin domain dynamic grating test principle, the delay of the first port 101 is T Path1 =2×n×(l 112a + l 112c + l 114a ) / c, the delay of the second port 102 is T Path2 =T Max -2×n×(l 115a + l 115b ) / c, the length of the optical fiber sensitive ring 12 is l Fiber =c×(T Path2 -T Path1 ) / (2×n), information range (T Path1 , T Path2 ), and then compare the fiber lengths obtained from the two measurements to verify the accuracy of the measurement results;

[0030] According to the test results of Brillouin domain and coherent domain and the temperature and strain parameters of the optical fiber itself, the temperature, strain and crosstalk information of the optical fiber sensitive ring 12 can be obtained. According to the test results of Brillouin domain and coherent domain and the temperature and strain parameters of the optical fiber itself, the temperature, strain and crosstalk information of the optical fiber sensitive ring 12 can be obtained.

[0031] The optical transmission path inside the optical path adapter module 11 and the realization process of simultaneous measurement are as follows: the simultaneous measurement of temperature, strain, and crosstalk information of the optical fiber sensitive ring 12 essentially relies on the Brillouin optical time domain analyzer 13 and the optical coherence domain polarization meter 14. Figure 2 As shown, when the Brillouin optical time domain analyzer 13 is used to test the optical fiber sensitive ring 12, according to the test principle of the Brillouin dynamic grating, the test process involves four kinds of light with different functions and frequencies, namely, two pump lights X-Pump1 and X-Pump2 injected into the optical fiber sensitive ring 12 from the fast axis in opposite directions, a probe light Y-Probe injected into the optical fiber sensitive ring 12 from the slow axis, and a reflected light Y-Ref emitted from the optical fiber sensitive ring 12 in the opposite direction to the probe light Y-Probe; the frequency difference between the pump lights X-Pump1 and X-Pump2 is the Brillouin frequency shift v of the optical fiber sensitive ring. B The frequency difference between the probe light Y-Probe and the pump light X-Pump1 is the birefringence frequency shift Δv of the fiber sensitive ring. Bire The frequency difference between the reflected light Y-Ref and the probe light Y-Probe is the Brillouin frequency shift v of the fiber sensitive ring. B ;

[0032] like Figure 3 As shown, when the optical coherence domain polarimeter 14 is used to test the optical fiber sensitive ring 12, according to the principle of white light interferometry, the test process designs three kinds of light with different functions and consistent wavelengths, namely: the high-biased wide-spectrum light X-Input injected from the fast axis into the optical fiber sensitive ring 12, the transmission light X-Output output from the fast axis of the optical fiber sensitive ring 12, and the coupling light Y-Couple output from the slow axis of the optical fiber sensitive ring 12. The function of the optical path adapter module 11 is to merge and separate the above-mentioned seven kinds of light with different functions, and to achieve simultaneous measurement while ensuring the measurement accuracy. It should be noted that the Brillouin optical time domain analyzer 13 and the optical coherence domain polarimeter 14 operate in different bands and have different light source types. This is the premise that the optical path adapter module 11 can achieve simultaneous measurement.

[0033] like Figure 4 As shown, the semi-closed loop composed of the optical path adapter module 11 and the optical fiber sensitive ring 12 is expanded to facilitate the analysis of the optical transmission situation and the test process inside the optical path adapter module 11. The propagation paths of the 7 beams of light used for the test of the Brillouin optical time domain analyzer 13 and the optical coherence domain polarization meter 14 in the optical path adapter module 11 are as follows: the low-polarization broad spectrum light is input from the third port 103, and is polarized to the fast axis after passing through the 0° optical fiber polarizer 111 to form the high-polarization broad spectrum light X-Input; the fast-axis transmitted pump light X-Pump1 is input from the fourth port 104, and enters the polarization-maintaining fiber coupler 113 through the optical fiber polarization beam splitter port 112b, and is coupled with the fast-axis transmitted broad spectrum light X-Input. The mixed light enters the fast axis branch of the second optical fiber polarization beam splitter 114 through the output end 113a of the polarization-maintaining optical fiber coupler, and is injected into the optical fiber sensitive ring 12; the pump light X-Pump2 of fast axis transmission is input from the fifth port 105, and is injected into the optical fiber sensitive ring 12 through the polarization-maintaining optical fiber circulator 115; the probe light Y-Probe of slow axis transmission is input from the fourth port 104, and is injected into the optical fiber sensitive ring 12 after passing through the slow axis branches of the first optical fiber polarization beam splitter 112 and the second optical fiber polarization beam splitter 114.

[0034] Brillouin dynamic grating generation process, such as Figure 2 As shown, inside the optical fiber sensitive ring 12, the pump lights X-Pump1 and X-Pump2 transmitted in opposite directions along the fast axes meet in the optical fiber sensitive ring 12 to form a stable Brillouin dynamic grating BDG, and the detection light Y-Probe transmitted along the slow axis reads the dynamic grating formed by the pump light to form a reflected light Y-Ref carrying information, and the reflected light Y-Ref returns along the transmission path of the Y-Probe, and is finally output from the fourth port 104. The delay and frequency information of the reflected light Y-Ref are demodulated to obtain the distributed Brillouin frequency shift and birefringence frequency shift of the optical fiber sensitive ring 12.

[0035] Polarization coupling processes, such as Figure 3 As shown, when the wide-spectrum light X-Input transmitted along the fast axis passes through the polarization crosstalk point in the ring, polarization coupling occurs, and a small portion of the energy is coupled from the fast axis to the slow axis to form coupled light Y-Couple. After several couplings, the remaining light along the fast axis is the transmission light X-Output. After the transmission light X-Output and the coupled light Y-Couple pass through the polarization-maintaining fiber circulator 115, they enter the 45° fiber analyzer and are finally output from the sixth port 106. According to the optical path difference and interference intensity between the transmission light X-Output and the coupled light Y-Couple, the distributed polarization crosstalk of the fiber sensitive ring 12 can be obtained.

[0036] The present invention provides a device for simultaneously measuring the temperature, strain and crosstalk of an optical fiber sensitive ring. The device combines and separates the optical signals of a Brillouin optical time domain analyzer and an optical coherence domain polarization measuring instrument through an optical path adapter module, thereby realizing the simultaneous measurement of the temperature, strain and crosstalk of an optical fiber sensitive ring.

[0037] Compared with the prior art, the advantages of the present invention are: a new measuring device is designed to achieve simultaneous measurement of the temperature, strain and crosstalk of the optical fiber sensitive ring, providing support for the comprehensive analysis of the multi-parameters of the optical fiber sensitive ring. Compared with the existing optical fiber sensitive ring test device, the device of the present invention can obtain the three physical parameters of the optical fiber sensitive ring through one measurement. On the one hand, it avoids the repeated welding of the optical path during the test of the existing method, simplifies the test process and improves the test efficiency; on the other hand, it eliminates the influence of external factors on the existing test method and improves the accuracy of the test. The optical path switching part adopts a modular design. The optical path switching module designed on the basis of the existing commercial Brillouin dynamic grating equipment and optical coherence domain measurement equipment only needs to be connected between the optical fiber sensitive ring and the equipment when in use, and there is no need to modify the internal optical path of the existing equipment; at the same time, the module uses a small number of optical devices, a simple structure and a low construction cost. The performance of the test device depends on the Brillouin dynamic grating equipment and optical coherence domain measurement equipment used, and the optical path switching module will not affect the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the optical path structure of a device for simultaneously measuring temperature, strain and crosstalk of an optical fiber sensitive ring;

[0039] Figure 2 This is a schematic diagram of the generation process and test principle of polarization-maintaining fiber Brillouin dynamic grating;

[0040] Figure 3 This is a schematic diagram of the polarization coupling process and testing principle of polarization-maintaining optical fiber;

[0041] Figure 4 It is a schematic diagram of the internal optical path and working principle of the optical path adapter module; DETAILED DESCRIPTION

[0042] In order to clearly illustrate the device for simultaneously measuring temperature, strain and crosstalk of an optical fiber sensitive ring proposed in 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.

[0043] The optical path structure of the optical fiber sensitive ring temperature, strain, and crosstalk simultaneous measurement device is as follows: Figure 1 As shown, the parameters of each optical device in the device are selected as follows:

[0044] The working wavelength of the 0° optical fiber polarizer 111 is 1550nm, the polarization extinction ratio is greater than 30dB, and the insertion loss is less than 1dB;

[0045] The first optical fiber polarization beam splitter 112 and the second optical fiber polarization beam splitter 114 are three-port devices, and both are polarization-maintaining pigtail input / output, the device operating wavelength is 1550nm, the insertion loss is less than 0.6dB, the extinction ratio is greater than 22dB, and the return loss is greater than 50dB;

[0046] The polarization-maintaining fiber coupler 113 has an operating wavelength of 1550 nm, an insertion loss of less than 1 dB, an extinction ratio of greater than 25 dB, a splitting ratio of 50:50, and a return loss of greater than 55 dB;

[0047] The polarization-maintaining fiber circulator 115 is a three-port circulator, and its optical transmission direction is the first input end 115a of the polarization-maintaining circulator→the second input end 115b of the polarization-maintaining circulator→the third output end 115c of the polarization-maintaining circulator, the operating wavelength is 1550nm, the single-port insertion loss is less than 1dB, the extinction ratio is greater than 22dB, and the return loss is greater than 50dB;

[0048] The operating wavelength of the 45° optical fiber analyzer 116 is 1550 nm, the polarization extinction ratio is less than 0.2 dB, and the insertion loss is less than 1 dB.

[0049] The optical device is used to construct an optical path switching module, and a polarization-maintaining optical fiber ring is measured according to the measurement method;

[0050] First, build the optical path according to the optical path structure diagram, determine the optical fiber lengths of the 0° optical fiber polarizer input end 111a, the 0° optical fiber polarizer output end 113b, the first optical fiber polarization beam splitter input end 112a, the first optical fiber polarization beam splitter first output end 113c, the polarization-maintaining optical fiber coupler output end 113a, the second optical fiber polarization beam splitter output end 114a, and the optical fiber lengths of the polarization-maintaining circulator first input end 115a, the polarization-maintaining circulator second input end 115b, and the 45° optical fiber analyzer input end 116b, and record them in sequence as: l111a , l 113b , l 112a , l 113c , l 113a , l 114a , l 115a , l 115b , l 116b ;

[0051] Calculate the spatial optical path difference corresponding to the optical fiber length from the 0° optical fiber polarizer output end 113b, the first polarization beam splitter first output end 113c, the first polarization beam splitter second output end 112c to the second polarization beam splitter, the polarization-maintaining circulator first input end 115a, the polarization-maintaining circulator second input end 115b, and the 45° optical fiber analyzer input end 116b, and record them in sequence as: S 113b , S 113c , S 112c , S 115a , S 115b , S 116b , if the birefringence of the polarization-maintaining fiber is Δn, then the calculation method of the spatial optical path difference of a certain section of fiber is: the actual length of the fiber × birefringence Δn;

[0052] The two free ports of the optical fiber sensitive ring 12 are respectively fused with the first port 101 and the second port 102 of the optical path adapter module 11, and the axial angle of the optical fiber during fusion is 0°;

[0053] The detection light output port of the Brillouin optical time domain analyzer 13 is connected to the fourth port 104 of the optical path adapter module 11, and the other port is connected to the fifth port 105 of the optical path adapter module 11; the low-bias wide-spectrum light output port of the optical coherence domain polarization meter 14 is connected to the third port 103 of the optical path adapter module 11, and the other port is connected to the sixth port 106 of the optical path adapter module 11; the above connection methods all adopt flange connection;

[0054] Then, the Brillouin optical time domain analyzer 13 is started to test the Brillouin frequency shift of the optical fiber sensitive ring 12, and the Brillouin frequency shift test result is recorded; the Brillouin optical time domain analyzer 13 and the optical coherence domain polarization meter 14 are started to test the optical fiber sensitive ring at the same time; after the test is completed, the data is saved, and the distributed polarization crosstalk test result is dispersion compensated and normalized, and the test data after dispersion compensation is saved;

[0055] Then record the polarization crosstalk peak (S Max , ρ), according to the principle of white light interferometry, the optical path differences corresponding to the first port 101 and the second port 102 are: S Path1 = S Path1 =S Max -(S 113b+S 113a +S 114a ), S Path2 =S 116b +S 115c The length of the optical fiber sensitive ring 12 is l Fiber =(S Path1 -S Path2 ) / Δn, the information range of distributed polarization crosstalk is (S Path2 , S Path1 );

[0056] Record the maximum delay T in the Brillouin domain test results Max According to the Brillouin domain dynamic grating test principle, the delays of the first port 101 and the second port 102 are: T Path1 =2×n×(l 112a + l 112c + l 114c + l 114a ) / c、T Path2 =T Max -2×n×(l 115a + l 115b ) / c, assuming that the refractive index of the optical fiber is n; then the length of the optical fiber sensitive ring 12 is l Fiber =c×(T Path2 -T Path1 ) / (2×n), information range (T Path1 , T Path2 ); if l Fiber1 ≈l Fiber2 , it can be considered that the test results are accurate and valid.

[0057] By substituting the Brillouin domain and coherence domain test results into the temperature and strain parameters of the optical fiber itself, the temperature, strain and crosstalk information of the optical fiber sensitive ring 12 can be obtained.

[0058] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for simultaneously measuring temperature, strain and crosstalk of an optical fiber sensitive ring, comprising: The optical path switching module (11), the Brillouin optical time domain analyzer (13), and the optical coherence domain polarization measuring instrument (14) are characterized by: 1) The pump light, the detection light and the low-bias wide spectrum light outputted by the Brillouin optical time domain analyzer (13) and the optical coherence domain polarization measuring instrument (14) enter the optical fiber sensitive ring (12) via the optical path adapter module (11), and the signal light carrying the temperature, strain and crosstalk of the optical fiber sensitive ring (12) returns to the Brillouin optical time domain analyzer (13) and the optical coherence domain polarization measuring instrument (14) via the optical path adapter module (11) for demodulation, and the optical signals of the two instruments are coupled and separated by the optical path adapter module (11), so as to realize the simultaneous measurement of the temperature, strain and crosstalk of the optical fiber sensitive ring (12); 2) The Brillouin optical time domain analyzer (13) is connected to the optical path adapter module (11) in the following manner: the Brillouin optical time domain analyzer (13) is connected to the optical path adapter module (11) via a fourth port (104) of the optical path adapter module (11), and is connected to the optical path adapter module (11) via a fifth port (105) of the optical path adapter module (11), wherein the detection light output port of the Brillouin optical time domain analyzer (13) is connected to the fourth port (104); 3) The optical coherence domain polarimeter (14) is connected to the optical path adapter module (11) in the following manner: the optical coherence domain polarimeter (14) is connected to the optical path adapter module (11) via the third port (103) and the sixth port (106) of the optical path adapter module (11), wherein the low-bias wide-spectrum light output port of the optical coherence domain polarimeter (14) is connected to the third port (103).

2. The optical path adapter module (11) according to claim 1, characterized in that: The optical path transfer module (11) is composed of a 0° optical fiber polarizer (111), a first optical fiber polarization beam splitter (112), a second optical fiber polarization beam splitter (114), a polarization-maintaining optical fiber coupler (113), a polarization-maintaining optical fiber circulator (115), and a 45° optical fiber analyzer (116).

3. The optical path adapter module (11) according to claim 1, characterized in that: 1) The 0° optical fiber polarizer output end (111b) of the 0° optical fiber polarizer (111) is connected to the polarization-maintaining optical fiber coupler (113), the first output end (113c) of the first optical fiber polarization beam splitter is connected to the polarization-maintaining optical fiber coupler (113), the second output end (112c) of the first optical fiber polarization beam splitter is connected to the second optical fiber polarization beam splitter (114), and the polarization-maintaining optical fiber coupler output end (113a) is connected to the second optical fiber polarization beam splitter (114); the 45° optical fiber analyzer input end (116b) is connected to the polarization-maintaining optical fiber circulator (115), and all of the above connection points are connected by fusion splicing, and the fusion splicing axis angles are all 0°; 2) The optical path adapter module (11) comprises a total of 6 input and output ports, wherein the first port (101) is connected to the second optical fiber polarization beam splitter (114), the second port (102) is connected to the polarization-maintaining optical fiber circulator (115), the third port (103) is connected to the 0° optical fiber polarizer (111), the fourth port (104) is connected to the first optical fiber polarization beam splitter (112), the fifth port (105) is connected to the corresponding polarization-maintaining optical fiber circulator (115), and the sixth port (106) is connected to the 45° optical fiber polarization analyzer (116) via the 45° optical fiber polarization analyzer output end (116a); 3) The first port (101) and the second port (102) are access ports for the optical fiber sensitive ring (12), the third port (103) is a low-bias wide-spectrum light input port, the fourth port (104) is a pump light, detection light and reflected light input / output port, the fifth port (105) is a pump light input port, and the sixth port (106) is a transmission light and coupling light output port; wherein the fourth port (104) and the fifth port (105) are access ports for the Brillouin optical time domain analyzer (13), and the third port (103) and the sixth port (106) are access ports for the optical coherence domain polarimeter (14).

4. The optical path adapter module (11) according to claim 1, comprising 6 optical devices in total, characterized in that: The working axis of the 0° optical fiber polarizer (111) is a fast axis, the input end (111a) of the 0° optical fiber polarizer is a single-mode input end, the output end (113b) of the 0° optical fiber polarizer is a polarization-maintaining output end, the working axis of the 45° optical fiber analyzer (116) is aligned at 45° with the fast axis of the pigtail, in addition, the output end (116a) of the 45° optical fiber analyzer is a single-mode output end, the input end (116b) of the 45° optical fiber analyzer is a polarization-maintaining input end, the first optical fiber polarization beam splitter (112) and the second optical fiber polarization beam splitter (114) are three-port devices, and both are polarization-maintaining pigtail input / output, wherein the first output end (113c) of the first optical fiber polarization beam splitter and the output end (113c) of the polarization-maintaining optical fiber coupler are fast-axis output / input ends, and the second output end (112c) of the first optical fiber polarization beam splitter is a slow-axis output / input end.

5. The polarization-maintaining fiber coupler (113) according to claim 4, characterized in that: The polarization-maintaining fiber coupler (113) is a three-port device, and the splitting ratio between the 0° fiber polarizer output end (113b) and the first output end (113c) of the first polarization beam splitter is 50:

50. Meanwhile, the polarization-maintaining fiber circulator (115) is a three-port device, and its optical transmission path is the first input end (115a) of the polarization-maintaining circulator→the second input end (115b) of the polarization-maintaining circulator→the input end (116b) of the 45° fiber analyzer.

6. The solution for realizing simultaneous measurement of temperature, strain and crosstalk of an optical fiber sensitive ring by the optical path adapter module (11) according to claim 1, wherein the steps are: 1) constructing an optical path according to the optical path structure diagram, determining the optical fiber lengths of the 0° optical fiber polarizer input end (111a), the 0° optical fiber polarizer output end (113b), the first optical fiber polarization beam splitter input end (112a), the first optical fiber polarization beam splitter first output end (113c), the polarization-maintaining optical fiber coupler output end (113a), and the second optical fiber polarization beam splitter output end (114a), and The optical fiber lengths of the first input end (115a) of the polarization-maintaining circulator, the second input end (115b) of the polarization-maintaining circulator, and the input end (116b) of the 45° optical fiber analyzer are recorded as follows: l 111a , l 113b , l 112a , l 113c , l 113a , l 114a , l 115a , l 115b , l 116b ; 2) Calculate the spatial optical path difference corresponding to the optical fiber length from the output end (113b) of the 0° optical fiber polarizer, the first output end (113c) of the first polarization beam splitter, the second output end (112c) of the first polarization beam splitter to the second polarization beam splitter, the first input end (115a) of the polarization-maintaining circulator, the second input end (115b) of the polarization-maintaining circulator, and the input end (116b) of the 45° optical fiber analyzer, and record them in sequence as: S 113b , S 113c , S 112c , S 115a , S 115b , S 116b , if the birefringence of the polarization-maintaining fiber is Δn, then the calculation method of the spatial optical path difference of a certain section of fiber is: the actual length of the fiber × birefringence Δn; 3) welding the two free ports of the optical fiber sensitive ring (12) to the first port (101) and the second port (102) of the optical path adapter module (11) respectively, and the axial angle of the optical fiber during welding is 0°; 4) connecting the detection light output port of the Brillouin optical time domain analyzer (13) to the fourth port (104) of the optical path adapter module (11), and connecting the other port to the fifth port (105) of the optical path adapter module (11); connecting the low-bias wide-spectrum light output port of the optical coherence domain polarization meter (14) to the third port (103) of the optical path adapter module (11), and connecting the other port to the sixth port (106) of the optical path adapter module (11); the above connection methods all adopt flange connection; 5) Start the Brillouin optical time domain analyzer (13), set the measurement range and the sweep frequency range, ensure that the information of the optical fiber sensitive ring (12) can be completely obtained, and perform a preliminary test on the optical fiber sensitive ring (12); After the test is completed, the Brillouin frequency shift of the optical fiber sensitive ring (12) is read and recorded; if the Brillouin frequency shift parameters of the optical fiber sensitive ring (12) are known, this step can be skipped; 6) Start the Brillouin optical time domain analyzer (13) and the optical coherence domain polarization measuring instrument (14), adjust the Brillouin optical time domain analyzer (13) to the Brillouin dynamic grating mode, input the Brillouin frequency shift and other parameters of the optical fiber sensitive ring (12), set a larger measurement range (sweep range), ensure that the optical fiber sensitive ring (12) information can be fully obtained, and test the optical fiber sensitive ring at the same time; after the test is completed, save the data, and perform dispersion compensation and normalization on the distributed polarization crosstalk test results, and save the test data after dispersion compensation; 7) Determining the information range of the optical fiber sensitive ring (12) in the test results after polarization crosstalk dispersion compensation; the range is determined based on the polarization crosstalk peak corresponding to the fusion point at the first port (101) and the second port (102), and the specific process is: recording the polarization crosstalk peak (S Max , ρ), according to the measured optical fiber length and its corresponding optical path difference, it can be known from the principle of white light interferometry that the polarization crosstalk peak optical path difference corresponding to the second port (102) in the test result is: S Path2 = S 116b +S 115c , the polarization crosstalk peak optical path difference corresponding to the first port (101) in the test results is: S Path1 =S Max -(S 113b + S 113a +S 114a ), the length of the optical fiber sensitive ring (12) is l Fiber =(S Path1 -S Path2 ) / Δn, information range (S Path2 , S Path1 ); 8) Determine the information range of the optical fiber sensitive ring (12) in the Brillouin domain test result, the range is realized based on the delay between the first port (101) and the second port (102), and the specific process is: record the maximum delay T in the test result Max Assuming that the refractive index of the fiber is n, according to the Brillouin domain dynamic grating test principle, the delay of the first port (101) is T Path1 =2×n×(l 112a + l 112c + l 114a ) / c, the delay of the second port (102) is T Path2 = T Max -2×n×(l 115a + l 115b ) / c, the length of the optical fiber sensitive ring (12) is l Fiber = c×(T Path2 -T Path1 ) / (2×n), information range (T Path1 , T Path2 ), and then compare the fiber lengths obtained from the two measurements to verify the accuracy of the measurement results; 9) Based on the Brillouin domain and coherence domain test results and the temperature and strain parameters of the optical fiber itself, the temperature, strain and crosstalk information of the optical fiber sensitive ring (12) can be obtained.

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