CN106441353A - Fiber optic gyro ring polarization coupling symmetry assessment device - Google Patents

Abstract

The invention belongs to the technical field of optical fiber measurement, and in particular relates to a symmetry evaluation device for polarization coupling of an optical fiber gyroscope ring which can be used for on-line monitoring of the winding quality of the optical fiber gyroscope ring. A symmetry evaluation device for fiber optic gyroscope ring polarization coupling, including a light source device 10, a test device 11, a first optical path correlator 12A, a second optical path correlator 12B, a differential detection device 13, and a photoelectric signal conversion and signal recording device 14. The test device 11 includes a device under test 110, a first circulator 113A and a second circulator 113B connected to both ends of the device under test 110, a first polarizer 111A and a first analyzer 111B, a second A polarizer 112A and a second analyzer 112B. The invention can simultaneously realize the forward and reverse measurement of the polarization coupling information of the defect point of the optical fiber gyroscope ring, suppresses the measurement error caused by the inconsistency of the dispersion effect of the symmetrical point of the optical fiber gyroscope ring, and has a simple and effective structure.

Description

A Symmetry Evaluation Device for Fiber Optic Gyro Ring Polarization Coupling

technical field

The invention belongs to the technical field of optical fiber measurement, and in particular relates to a symmetry evaluation device for polarization coupling of an optical fiber gyroscope ring which can be used for on-line monitoring of the winding quality of the optical fiber gyroscope ring.

Background technique

As an important sensing unit in the field of navigation and guidance and a typical application of the reciprocity effect, gyroscopes are widely used due to their unique advantages. Compared with traditional mechanical gyroscopes, fiber optic gyroscopes have the advantages of light weight, small size, and anti-electromagnetic interference. The stability and reliability of the manufacturing process of the key sensitive component, the fiber optic gyro ring, will directly affect the overall quality and navigation accuracy of the fiber optic gyroscope. According to the Sagnac effect, we know that the forward and reverse transmission light in the fiber optic gyro ring needs exactly the same optical path information to carry out accurate navigation. In 1980, Shupe et al. found that temperature changes in the environment can cause the non-reciprocity of the fiber optic gyroscope, resulting in a large gyroscope drift. The inconsistency of the optical path of the forward light and the reverse light in the fiber optic gyroscope ring is an important factor affecting the performance of the fiber optic gyroscope.

As for how to reduce the non-reciprocal effect caused by heat in the fiber optic gyro ring, many solutions have been proposed. In 2012, Song Ningfang and others from Beihang University disclosed a top-down symmetrical cross-wound fiber optic gyro ring structure for fiber optic gyroscopes (Chinese patent application number: 201210043894.3). The optical fiber coil is divided into upper and lower parts, and one side has no structural constraints, and will not be squeezed under the conditions of vibration and temperature changes; through crossing, the coils on both sides contain forward and reverse optical fibers of the same length, so that the axial It is equal to the temperature modulation produced by the radial temperature gradient on the optical fiber. The symmetrical winding method of the fiber optic gyroscope improves its forward and reverse transient characteristics to a certain extent. However, the slight asymmetry of the fiber optic gyro ring about the center point of the winding fiber will greatly weaken the advantages of the symmetrical winding method. In 2012, Yang Dewei of Beihang University and others disclosed a method for estimating and symmetry evaluating crosstalk of optical fiber gyroscope ring polarization (Chinese patent application number: CN201210359805.6). While measuring the polarization coupling intensity distribution of the fiber optic gyro ring, the birefringence dispersion coefficient of the fiber to be tested is obtained by using the wavelength scanning method, and the polarization crosstalk estimation model is established to determine the midpoint of the fiber optic gyro ring and obtain the polarization crosstalk data on the left and right sides of the midpoint. The polarization crosstalk value is used as a reference index to evaluate the symmetry of the fiber optic gyroscope. The invention is applied to measure the winding of various polarization-maintaining optical fibers, which is convenient for optimizing the selection of optical fibers for gyroscopes, and is of great significance for evaluating and guiding the optimization of the temperature performance of optical fiber gyroscopes.

Optical coherent domain polarization technology (OCDP) is an extremely superior distributed measurement technology. He uses a scanning optical interferometer to compensate the optical path, realize the interference between different coupling modes, locate the position of the internal defect of the wound fiber, and use the interference intensity to analyze the polarization coupling strength of the defect point. In 2011, Yang Jun and others from Harbin Engineering University disclosed a device and method for improving the measurement accuracy and symmetry of polarization-maintaining optical fiber polarization coupling (Chinese patent application number: 201110118450.7). Through the optical signal controllable reversing mechanism, the forward and reverse measurements of the optical fiber gyroscope ring to be tested can be realized respectively. The invention provides a device capable of reducing the influence of birefringence dispersion on measurement accuracy, and has very important practical value for parameter measurement and performance evaluation of an optical fiber gyro ring. In the same year, Yang Jun and others from Harbin Engineering University provided a device that reduces the influence of birefringence dispersion on the polarization coupling measurement of polarization-maintaining fiber (Chinese patent application number: CN201110118127.X). The invention uses a semi-reflective and semi-transparent polarization rotator to divide the broad-spectrum light into two beams on average, realizes passing through the optical fiber to be tested from the forward and reverse directions at the same time, and using the same polarization coupling detection device, can simultaneously obtain two beams with symmetrical scanning positions Amplitude polarization coupling measurement data.

However, although the measurement methods mentioned above can realize forward and reverse measurements or evaluate the symmetry of the fiber optic gyroscope: the wavelength scanning method of Song Ningfang et al. is only one of the polarization couplings of the left and right intervals of the fiber optic gyroscope ring. Average value, there is no way to achieve distributed measurement; the controllable reversing mechanism of Yang Jun et al. did not achieve simultaneity, and the influence of environmental parameters such as temperature when the time is inconsistent cannot be ruled out; Simultaneity is achieved, but the forward and reverse measurements are not exactly the same path. These solutions based on OCDP technology lack certain feasibility, the online real-time monitoring effect is greatly reduced, and there is no effective evaluation standard when analyzing the full-temperature characteristics of the fiber optic gyro ring. Therefore, a new method is needed to evaluate the symmetry and quality of the fiber optic gyro ring, and provide real-time effective monitoring and necessary guidance for the selection of optical fiber and the improvement of the ring process.

Contents of the invention

The purpose of the present invention is to propose a symmetry evaluation device for the polarization coupling and symmetry of the fiber optic gyro ring, which can simultaneously measure the forward and reverse directions of the fiber optic gyro ring.

The purpose of the present invention is achieved like this:

A symmetry evaluation device for fiber optic gyroscope ring polarization coupling, including a light source device 10, a test device 11, a first optical path correlator 12A, a second optical path correlator 12B, a differential detection device 13, and a photoelectric signal conversion and signal recording device 14.

The test device 11 includes a device under test 110, a first circulator 113A and a second circulator 113B connected to both ends of the device under test 110, a first polarizer 111A and a first analyzer 111B, a second polarizer device 112A and the second analyzer 112B;

The first circulator 113A and the second circulator 113B have the same physical parameters, and the two ends of the device under test 110 are respectively connected to the second ports of the first circulator 113A and the second circulator 113B; the first polarizer 111A and The second polarizer 112A has the same polarizing angle, and the two are respectively connected to the first port of the first circulator 113A and the second circulator 113B; the first polarizer 111B and the second polarizer 112B have the same Angle of deflection analysis, the two are respectively connected to the third port of the first circulator 113A and the second circulator 113B;

The wide-spectrum light source 101 splits the light equally to the test device 11 through the first coupler 103; the two beams of light are respectively input through the two ends of the device under test 110, and simultaneously generate two sets of forward and reverse signals; the first optical path correlator 12A and the second optical path correlator 12B scan; finally output two polarization coupling signals with symmetrical scanning positions, so as to realize simultaneous forward and reverse testing of the device under test 110 .

The wide-spectrum light source 101 in the light source device 10 is split into the test device 11 via the first coupler 103 to perform polarization coupling test; the calibration light source 102 in the light source device 10 is split into the first optical path correlation through the second coupler 104 Perform scanning position correction in device 12A and second optical path correlator 12B;

The first optical path correlator 12A is composed of the third coupler 121A, the fourth coupler 122A, the third circulator 123A, the first collimator lens 124A and the scanning table 125; the wide-spectrum light source 101 passes through the device under test 110 and the testing device The devices in 11 are connected through the second analyzer 112B and the input end of the third coupler 121A; the correction light source 102 is connected through the second coupler 104 and the other input end of the third coupler 121A; the two of the fourth coupler 122A The output terminals are respectively connected to the first differential detector 130A and the second differential detector 130B; the data is collected through the data acquisition card 141, and transmitted to the host computer 142 to output the polarization coupling signal;

The physical parameters of the second optical path correlator 12A and the first optical path correlator 12A are consistent except that they share the scanning stage 125 .

The first circulator 113A and the second circulator 113B are three-port devices, and the light only propagates in one direction; if the signal is input from the first port 71A, it can only be output from the second port 71B; 2 port 71B input, then only the 3rd port 71C output; otherwise, can not transmit.

The test device 21 includes a device under test 110, a forward coupler 214A and a reverse coupler 214B connected to both ends of the device under test 110, a first polarizer 111A and a first polarizer 111B, a second polarizer 112A and the second polarizer 112B, the first isolator 213A and the second isolator 213B;

The two ends of the device under test 110 are respectively connected to one end of the forward coupler 214A and the reverse coupler 214B; The other end of the polarizer 214B is connected; the first polarizer 111A and the second polarizer 112A have the same polarizing angle, and they are respectively connected to the input port 72A of the first isolator 213A and the second isolator 213B; the first The polarizer 111B and the second polarizer 112B have the same polarizer angle, and are respectively connected to the other ends of the forward coupler 214A and the reverse coupler 214B.

The first isolator 213A or the second isolator 213B is input from the first port and output from the second port, light can only travel in one direction, and vice versa.

The beneficial effects of the present invention are:

1. It can realize the forward and reverse measurement of the polarization coupling information of the defect point of the fiber optic gyro ring at the same time, and suppress the measurement error caused by the inconsistency of the dispersion effect of the symmetrical point of the fiber optic gyro ring. The structure is simple and effective;

2. The test time of the fiber optic gyro ring polarization coupling measurement device is reduced, the measurement efficiency is high, and the influence of environmental factors such as temperature is eliminated;

3. The polarization coupling symmetry of the fiber optic gyro ring can be accurately obtained. Since the forward and reverse measurements can be performed at the same time, two distributed polarization coupling measurement results symmetrical about the midpoint of the polarization maintaining fiber can be obtained at the same time.

Description of drawings

Fig. 1 is a schematic diagram of a symmetry evaluation device of a circulator-type fiber optic gyroscope ring polarization coupling;

Fig. 2 is a schematic diagram of a symmetry evaluation device of a coupler-type fiber optic gyroscope ring polarization coupling;

Fig. 3 is the structural representation of circulator and coupler;

Figure 4 is a schematic diagram of a typical fiber optic gyroscope ring polarization coupling evaluation device;

Figure 5 is a simplified optical path scheme for forward measurement and reverse measurement of the fiber optic gyro ring;

Fig. 6 is the polarization coupling signal output by the symmetry evaluation device for the polarization coupling of the fiber optic gyro ring.

Fig. 7 is a schematic diagram of the measuring device.

detailed description

The present invention will be further described below in conjunction with embodiment and accompanying drawing.

The invention provides a symmetry evaluation device for optical fiber gyroscope ring polarization coupling. It is characterized in that the white light source used by the device is divided into two beams on average; using directional optical devices to inject them into the forward and reverse directions of the fiber optic gyro ring to be tested; and then sharing the same scanning table with two relatively independent interferometers for Scanning; finally, using the optical coherent domain polarization measurement technology, two pieces of polarization coupling measurement data with symmetrical scanning positions are obtained at the same time. The device has simple structure and high measurement precision, and can reduce the influence of birefringence dispersion on polarization-maintaining optical fiber polarization coupling measurement. The invention has important practical value for the polarization coupling measurement and symmetry performance evaluation of the fiber optic gyro ring, and can be used to improve the fiber optic gyroscope surround manufacturing process and optimize the fiber optic gyroscope manufacturing process.

The device includes a light source device 10, a test device 11, optical path correlators 12A and 12B, a differential detection device 13, a photoelectric signal conversion and signal recording device 14, and is characterized in that:

(1) The test device 11 includes a device under test 110, a first circulator 113A and a second circulator 113B connected to both ends of the device under test 110, a first polarizer 111A and a first analyzer 111B, a first 2 polarizer 112A and second analyzer 112B.

(2) The first circulator 113A and the second circulator 113B have the same physical parameters, and the two ends of the device under test 110 are respectively connected to the second port 71B of the first circulator 113A and the second circulator 113B; The polarizer 111A and the second polarizer 112A have other physical parameters such as the same polarizing angle, and the two are respectively connected to the first port 71A of the first circulator 113A and the second circulator 113B; the first polarizer 111B and The second analyzer 112B has the same other physical parameters such as the analysis angle, and both are respectively connected to the third port 71C of the first circulator 113A and the second circulator 113B.

(3) The wide-spectrum light source 101 splits the light equally to the test device 11 through the first coupler 103; the two beams of light are respectively input through the two ends of the device under test 110, and simultaneously generate two sets of forward and reverse signals; The independent and shared optical path correlators 12A and 12B of the scanning table 125 scan; finally output two polarization coupling signals 143A and 143B with symmetrical scanning positions, so as to realize the forward and reverse simultaneous testing of the device under test 110 .

The symmetry evaluation device for the polarization coupling of a fiber optic gyro ring is characterized in that:

(1) The wide-spectrum light source 101 in the light source device 10 is split into the testing device 11 via the first coupler 103 to carry out the polarization coupling test; Scanning position correction is performed in the optical path correlators 12A and 12B.

(2) The first optical path correlator 12A is made up of the 3rd coupler 121A, the 4th coupler 122A, the 3rd circulator 123A, the 1st collimating lens 124A and the scanning platform 125; , and related devices in the testing device 11 are connected through the 2nd analyzer 112B and the input end of the 3rd coupler 121A; the correction light source 102 is connected with the other input end of the 3rd coupler 121A through the 2nd coupler 104; the 4th coupling The two output ends of the detector 122A are respectively connected to the differential detectors 130A and 130B; the data is collected through the data acquisition card 141, and transmitted to the host computer 142 to output polarization coupling signals 143A and 143B.

(3) The relatively independent second optical path correlator 12A and the first optical path correlator 12A share the scanning table 125 , and the physical parameters of other devices are correspondingly consistent.

The circulator 113A or 113B is a three-port device, and light can only travel in one direction. If the signal is input from the first port 71A, it can only be output from the second port 71B; if the signal is input from the second port 71B, it will be output from the third port 71C; otherwise, neither can be transmitted.

The symmetry evaluation device for the polarization coupling of a fiber optic gyro ring is characterized in that:

(1) The test device 21 includes a device under test 110, a forward coupler 214A and a reverse coupler 214B connected to both ends of the device under test 110, a first polarizer 111A and a first polarizer 111B, a first 2. Polarizer 112A, second analyzer 112B, first isolator 213A, and second isolator 213B.

(2) two ends of the device under test 110 are respectively connected to one end of the forward coupler 214A and the reverse coupler 214B; The other end of the reverse coupler 214B is connected; the first polarizer 111A and the second polarizer 112A have the same polarization angle and other physical parameters, and the two are respectively the same as those of the first isolator 213A and the second isolator 213B. The input port 72A is connected; the first polarizer 111B and the second polarizer 112B have the same other physical parameters such as the polarizer angle, and they are respectively connected to the other end of the forward coupler 214A and the reverse coupler 214B.

The aforementioned isolator 213A or 213B with optical fiber gyro polarization coupling is input from the first port 72A and output from the second port 72B. The light can only propagate in one direction, and vice versa.

Generally, a conventional optical fiber gyro ring polarization coupling measurement device is shown in FIG. 4 . For the evaluation of the polarization coupling of discontinuous points in polarization-maintaining fiber, an optical coherent domain polarization measurement device is used. The light emitted by the wide-spectrum light source (SLD) 101 passes through the polarizer 411A, the device under test 110, and the polarizer 411B in sequence, and is connected with the Mach-Zehnder interferometer (MZI) 42, and then connected with the differential detection device 43, and finally with the interference signal The detection is connected to the processing device 14; in addition, the correction light source 102 is used for the displacement correction of the displacement stage 425 in the Mach-Zehnder interferometer 42; the data is collected through the data acquisition card 441, and is transmitted to the upper computer 442 to output the polarization coupling signal 442, which only Contains forward information of the device under test 110 .

The symmetry evaluation device for the polarization coupling of the fiber optic gyro ring mentioned in the present invention measures the polarization coupling of the polarization-maintaining fiber simultaneously from the forward direction and the reverse direction. As shown in Figure 5, it is a simplified optical path scheme for two-way simultaneous measurement. Assuming that the device under test 110 is a panda-type polarization-maintaining fiber with a length of L, where the refractive index of the slow axis is n _slow and the refractive index of the fast axis is n _fast , then the difference between the refractive indices of the fast and slow axes of the polarization-maintaining fiber is Δn=n _slow -n _fast . Assuming that all transmitted light is input from the slow axis, there is a defect point at a distance x from the head end of the device under test 110 . The polarized light will be coupled at a distance x from the tip, and a small amount of transmitted light is coupled from the slow axis into the fast axis.

In the forward measurement and reverse measurement paths, the optical path traveled by the uncoupled transmitted light can be expressed as

S _transmission = n _slow L, (1)

In the forward measurement path, the optical path 51 traveled by the coupled light can be expressed as

S _{coupling_forward} = n _slow x + n _fast (Lx), (2)

In the reverse measurement path, the optical path 52 traveled by the coupled light can be expressed as

S _{coupling_forward} = n _slow (Lx) + n _fast x. (3)

For forward measurement, it can be seen from formulas (1) and (2) that the optical path difference between transmitted light and coupled light is

ΔS _forward = Δn·(Lx), (4)

For the reverse measurement, it can be seen from the formulas (1) and (3) that the optical path difference between the transmitted light and the coupled light is

ΔS _reverse = Δn·x. (5)

In accompanying drawing 5, there are two defect points symmetrical about the fiber optic gyroscope ring midpoint 53 (length is L/2) -- near head end defect point 54 (length is x ₁ ) and near tail end defect point 55 (length is x ₂ ), that is, the following relationship

L/2-x ₁ =x ₂ -L/2. (6)

Generally, in addition to the influence of environmental factors, the influence of dispersion in optical fiber is related to the length. When measuring in the forward direction, the optical path difference between the coupled light and the transmitted light passing through the near-end defect point 54 of the optical fiber to be tested is longer than that passing through the near-end defect point 55, so the influence of dispersion on the near-end defect point 54 is relatively large. Big.

At this time, when the forward measurement is adopted for the near-end defect point 54, according to formula (4) and formula (6), the optical path difference between the transmitted light and the coupled light is

ΔS _forward = Δn·(Lx ₁ ), (7)

When reverse measurement is used for the near-tail defect point 55, according to formula (5) and formula (6), the optical path difference between transmitted light and coupled light is

ΔS _reverse = Δn·x ₂ =Δn·(Lx ₁ ). (8)

It can be known from formula (7) and formula (8) that in the above optical path scheme, the position information about the polarization coupling point measured simultaneously in the forward direction and the reverse direction is symmetrical about the midpoint of the optical fiber. The dispersion in the optical fiber has the same influence on the central symmetrical defect point of the fiber optic gyro ring, that is, the polarization coupling measurement device proposed by the present invention can not only achieve the purpose of simultaneous measurement, but also eliminate the influence of dispersion during measurement.

Application Example 1

The measurement device is shown in Figure 1, and the device parameters are selected as follows:

(1) The central wavelength of the broadband light source 101 is 1550nm, the half-spectrum width is 45nm, the fiber output power is greater than 5mW, and the extinction ratio is greater than 6dB;

(2) The optical fiber device 110 to be tested is a 500m panda-type polarization-maintaining optical fiber;

(3) The operating wavelength of the first polarizer 111A, the first analyzer 111B, the second polarizer 112A and the second analyzer 112B is 1550nm, the extinction ratio is greater than 20dB, and the insertion loss is less than 3dB;

(4) The first circulator 113A and the second circulator 113B are three-port polarization-maintaining circulators, and the other circulators 123A and 123B are three-port single-mode optical fiber circulators, the return loss of which is greater than 55 dB, and the insertion loss is less than 1 dB;

(5) The working wavelength of fiber couplers 103, 104, 121A, 121B, 122A, 121B is 1310/1550nm, the splitting ratio is 50:50, and the insertion loss is less than 0.5dB;

(6) The operating wavelength of the collimating lenses 124A and 124B is 1550nm;

(7) The diameter of the mirror used in the displacement stage 125 is 20mm, and the average reflectivity is greater than 95%.

Combining the above conditions, the measured polarization coupling signal is shown in Figure 6, where Figures 6(a) and 6(b) are the forward measurement results and reverse measurement results of the 500m fiber optic gyro ring, respectively. For the sake of simplicity, we take the polarization coupling peaks caused by three typical defect points at the head end and the tail end as examples for analysis. Accompanying drawing 6 (a) characteristic peak 61,62,63 correspond respectively to accompanying drawing 6 (b) characteristic peak 61 ', 62 ', 63 ', among the accompanying drawing 6 (a) characteristic peak 64,65,66 respectively Corresponding to the characteristic peaks 64', 65', 66' in the accompanying drawing 6(b). Since the characteristic peaks (such as 64, 65, and 66) caused by the head end of the fiber optic gyro ring are greatly affected by dispersion, the peak broadening amplitude is reduced, and compared with the characteristic peaks caused by the tail end, it will cause a large error. Correspondingly, if compared with the characteristic peak at the corresponding scanning optical path difference position in Fig. 6(b), the symmetry information of the fiber optic gyro ring can be obtained.

Application Example 2

The measuring device is shown in FIG. 7 . Except that the testing device 71 is different from the testing device 11 in FIG. 1 , the rest of the two devices are basically the same.

(1) The test device 71 includes a device under test 110, a first circulator 113A and a second circulator 113B connected to both ends of the device under test (110), a polarizer 710, a coupler 711, a first polarizer Device 111B, second analyzer 112B.

(2) The first circulator 113A and the second circulator 113B have the same physical parameters, and the two ends of the device under test 110 are respectively connected to the second ports of the first circulator 113A and the second circulator 113B; The two output ends are respectively connected to the first port of the first circulator 113A and the second circulator 113B, and the input end of the coupler 711 is connected to the polarizer 710; the first polarizer 111B and the second polarizer 112B have The same other physical parameters such as the angle of deflection analysis are connected to the third ports of the first circulator 113A and the second circulator 113B respectively.

(3) The wide-spectrum light source 101 is connected to the input end of the polarizer 710 in the test device 71; two sets of forward and reverse signals are generated simultaneously through the two ends of the device under test 110, and two sets of relatively independent and shared scanning The optical path correlators 12A and 12B of the stage 125 scan; finally output two polarization coupling signals 143A and 143B with opposite scanning positions, so as to realize the forward and reverse simultaneous testing of the device under test 110 .

The selection of device parameters is similar to that of the application example 1, and the same polarization coupling signal as that shown in Fig. 6 can be obtained through measurement.

Claims (5)

1. A symmetry evaluation device for fiber optic gyroscope ring polarization coupling, comprising a light source device (10), a test device (11), a first optical path correlator (12A), a second optical path correlator (12B), a differential detection The device (13), the photoelectric signal conversion and signal recording device (14), are characterized in that: The test device (11) includes a device under test (110), a first circulator (113A) and a second circulator (113B) connected to both ends of the device under test (110), a first polarizer (111A) And the first polarizer (111B), the second polarizer (112A) and the second polarizer (112B); The first circulator (113A) and the second circulator (113B) have the same physical parameters, and the two ends of the device to be tested (110) are connected to the second circulator (113A) and the second circulator (113B) respectively. port connection; the first polarizer (111A) and the second polarizer (112A) have the same polarizing angle, and they are respectively connected to the first port of the first circulator (113A) and the second circulator (113B) connection; the first analyzer (111B) and the second analyzer (112B) have the same angle of analysis, and they are respectively connected to the third port of the first circulator (113A) and the second circulator (113B) ; The wide-spectrum light source (101) splits the light equally to the test device (11) through the first coupler (103); the two beams of light are respectively input through the two ends of the device under test (110), and simultaneously generate two sets of forward and reverse signals Scanning by the first optical path correlator (12A) and the second optical path correlator (12B); finally output two polarization coupling signals with symmetrical scanning positions to realize the forward and reverse simultaneous test. 2. the symmetry evaluation device of a kind of fiber optic gyroscope ring polarization coupling according to claim 1, it is characterized in that: The wide-spectrum light source (101) in the light source device (10) splits light into the test device (11) for polarization coupling testing via the first coupler (103); the correction light source (102) in the light source device (10) passes through the first 2 The coupler (104) splits the light into the first optical path correlator (12A) and the second optical path correlator (12B) to perform scanning position correction; The first optical path correlator (12A) is composed of the third coupler (121A), the fourth coupler (122A), the third circulator (123A), the first collimator lens (124A) and the scanning table (125); The wide-spectrum light source (101) is connected to the input end of the second analyzer (112B) and the third coupler (121A) through the device under test (110) and the device in the test device (11); the correction light source (102) is connected through the first The 2nd coupler (104) is connected to the other input end of the 3rd coupler (121A); the two output ends of the 4th coupler (122A) are connected to the first differential detector (130A) and the second differential detector (130B) respectively. ) connection; carry out data collection through data acquisition card (141), transmit to upper computer (142) output polarization coupling signal; Except that the second optical path correlator (12A) and the first optical path correlator (12A) share the scanning platform (125), the physical parameters of other devices are correspondingly consistent. 3. the symmetry evaluation device of a kind of fiber optic gyroscope ring polarization coupling according to claim 1, is characterized in that: described 1st circulator (113A) and the 2nd circulator (113B) are three-port devices, Light only propagates in one direction; if the signal is input from the first port (71A), it can only be output from the second port (71B); if the signal is input from the second port (71B), it can only be output from the third port (71C) output; otherwise, neither can be transmitted. 4. the symmetry evaluation device of a kind of fiber optic gyroscope ring polarization coupling according to claim 1, is characterized in that: The test device (21) comprises a device under test (110), a forward coupler (214A) and a reverse coupler (214B) connected to both ends of the device under test (110), a first polarizer (111A) And the first polarizer (111B), the second polarizer (112A) and the second polarizer (112B), the first isolator (213A) and the second isolator (213B); The two ends of the device to be tested (110) are respectively connected to one end of the forward coupler (214A) and the reverse coupler (214B); the output port (72B) of the first isolator (213A) and the second isolator (213B) ) are respectively connected to the other end of the forward coupler (214A) and the reverse coupler (214B); the first polarizer (111A) and the second polarizer (112A) have the same polarizing angle, and the two are respectively It is connected to the input port (72A) of the first isolator (213A) and the second isolator (213B); Connect with the other end of the forward coupler (214A) and the reverse coupler (214B) respectively. 5. the symmetry evaluation device of a kind of fiber optic gyroscope ring polarization coupling according to claim 1, is characterized in that: described 1st isolator (213A) or the 2nd isolator (213B) are input from the 1st port, Output from port 2, the light can only travel in one direction, otherwise it cannot be transmitted.