Fiber-optic gyroscope thermally induced null drift range optimization method for tail fiber length quantitative control

Abstract

The invention discloses a fiber-optic gyroscope thermally induced null drift range optimization method for tail fiber length quantitative control, and belongs to the field of fiber-optic gyroscopes and optical measurement. The method is characterized in that in-loop temperature and thermal strain distribution is obtained by combining polarization-maintaining OFDR with a multi-parameter decoupling technology at a certain temperature change rate; calculating the refractive index variation to forecast the null drift of each temperature point; further forecasting the relationship between the null drift and the length change of the tail fiber of the optical fiber ring under all the temperature points, and determining the optimization direction and the optimization length Lmin of the tail fiber applicable to all the temperature points; and the length of the tail fiber is quantitatively controlled, and the geometric symmetry of the fiber ring is corrected so as to optimize the null drift performance of the ring. The method belongs to a quantitative fiber-optic gyroscope thermally induced null drift optimization method, null drift range optimization of all temperature points can be realized through one-time correction based on theoretical forecast, traditional qualitative tail fiber adjustment is improved into quantitative control of tail fiber length, the optimization process flow is simple, and the method plays an important role in performance improvement of a fiber-optic gyroscope system.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber gyroscope and optical measurement, and relates to a method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length. Background Art

[0002] The fiber optic gyroscope is an angular velocity sensor based on the principle of the Sagnac effect. With its structure that does not require moving parts or wearing parts, as well as its high precision and simple manufacturing process, it has quickly replaced the mechanical gyroscope and laser gyroscope that were previously developed and has broad application prospects in many fields.

[0003] The fiber ring is the core component of the fiber optic gyroscope. As the "brain" of the fiber optic gyroscope inertial navigation technology, it senses external attitude changes and is very sensitive to temperature and strain changes. In the actual operation of the fiber optic gyroscope, when the internal heat and the change of ambient temperature are applied to a section of optical fiber in the fiber ring, it will cause temperature disturbance. Unless the section of optical fiber is located in the middle of the fiber ring, a non-reciprocal phase shift will inevitably occur. Since the non-reciprocal phase shift cannot be distinguished from the phase difference caused by rotation, the fiber optic gyroscope will produce a large drift error, affecting the output accuracy of the fiber optic gyroscope.

[0004] At present, fiber optic rings generally adopt improved winding processes to improve symmetry, such as using quadrupoles, octopoles and hexadecoles, but the fiber optic ring winding technology is complex, and it is difficult to ensure the perfect symmetry of the fiber optic ring during the winding process. The geometric symmetry of the fiber optic sensitive ring describes the symmetric nature of its structure, which is affected by the winding method, winding defects and the midpoint position of the length. Among them, the midpoint deviation of the length is the main factor causing the geometric symmetry error. Therefore, the zero drift can be optimized by adjusting the geometric symmetry of the fiber optic sensitive ring by controlling the length of the pigtail, but the key is to accurately control the length of the pigtails on both sides. The traditional method is to repeatedly cut the pigtail and continuously test to obtain the zero drift result of the gyroscope, which has certain blindness and irreversibility. When the cutting length is greater than the length required for zero drift performance optimization, it will cause waste and fail to achieve the optimization goal; even if good results are obtained, it is impossible to summarize the rules and generalize them to other fiber optic sensitive rings for zero drift optimization.

[0005] In 2011, Yao Xiaotian of Suzhou Guanghuan Technology Co., Ltd. proposed to conduct dynamic characteristic detection on the optical fiber sensitive ring to be tested, so as to calculate the equivalent asymmetric length of the optical fiber ring, and then increase or decrease the length of the pigtails of the two arms according to the difference in the equivalent asymmetric length between the two arms to compensate for the asymmetric length, so as to achieve the goal of optimizing the performance of the optical fiber ring. (A method for improving the quality of optical fiber rings using compensation technology, CN 201110040569.7) Later in 2013, Yao Xiaotian and others proposed to assemble a fiber optic gyroscope system integrated into the optical fiber ring to be tested, and apply radial temperature excitation to it while measuring the rotation speed of the optical fiber ring to obtain the pointing thermal error angle of the gyroscope system. According to the two parameters of the rotation speed and the pointing thermal error angle, the pointing error temperature sensitivity coefficient of the optical fiber ring to be tested can be calculated to determine its equivalent asymmetric length. Finally, the asymmetric length is reduced by compensating the pigtail length, so as to improve the quality of the optical fiber ring. (A method and device for detecting the quality of optical fiber rings for gyroscopes, CN201210523580.3)

[0006] The above methods all require a complete set of fiber optic gyroscope test systems, and the pigtail on one side of the fiber optic ring needs to be repeatedly cut or extended to obtain the output of the fiber optic ring detection device under different compensation fiber lengths to determine whether the pigtail control length optimized for its best performance is achieved. The entire set of calculation processes and operations are numerous and complicated, making it difficult to apply in practice.

[0007] Zhao Wei and others from the 41st Institute of China Electronics Technology Group used the BOTDA technology to measure the stress distribution of the optical fiber ring at different temperatures, and then calculated the asymmetric length by calculating the stress integral difference, so as to cut the pigtail on one side to achieve the purpose of optimizing the zero drift performance of the optical fiber gyroscope. (Method for compensating the asymmetric length of the optical fiber ring for the optical fiber gyroscope, CN 201510282059.9) However, the stress distribution of the optical fiber ring measured by the BOTDA technology has low measurement accuracy and spatial resolution, and it is ultimately difficult to achieve accurate calculation of the length of the pigtail cut from the optical fiber ring, which cannot meet the requirements of zero drift optimization of the optical fiber ring.

[0008] Relatively speaking, the distributed strain measurement technology based on optical frequency domain Rayleigh scattering detection has higher spatial resolution and measurement accuracy, and can provide accurate measurement data for zero drift prediction and optimization of optical fiber sensitive rings.

[0009] In view of the problems that the current method of optimizing the zero drift of the optical fiber sensitive ring by controlling the length of the optical fiber ring pigtail cannot accurately complete the correction of the pigtail length at one time to achieve the best optimization of zero drift, and the operations are numerous and the process is complicated, the present invention discloses a method for optimizing the thermally induced zero drift extreme difference of an optical fiber gyroscope with quantitative control of the pigtail length. The best optimized pigtail direction and length are determined by the relationship between the zero drift and the change of the pigtail length in different lateral directions of the optical fiber ring, and then the pigtail on the corresponding side is cut or lengthened to the optimal pigtail length to adjust the geometric symmetry of the ring to achieve the optimization of the zero drift of the optical fiber sensitive ring. Only one pigtail correction is required to achieve the optimization of the zero drift of the optical fiber ring, and the corrected length of the pigtail is accurate, which significantly improves the quality of the optical fiber ring in practical applications. Summary of the invention

[0010] The purpose of the present invention is to propose a method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length, which solves the problem in the background technology that it is difficult to accurately complete the correction of the pigtail in one time to achieve zero drift optimization.

[0011] 1. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length, characterized in that: based on the principle that adjusting the pigtails on different sides of an optical fiber ring and the corresponding lengths can optimize its zero drift, the optimal pigtail length is determined through the relationship between zero drift and the change in the pigtail length on different sides of the optical fiber ring, and then the pigtail on the corresponding side is cut or lengthened to the optimal pigtail length to adjust the geometric symmetry of the ring, thereby optimizing the zero drift of the optical fiber sensitive ring, and the specific steps are:

[0012] Step 1 (101): placing the optical fiber sensitive ring (501) in a temperature box (502), testing the optical fiber sensitive ring (501) by using a polarization-maintaining OFDR multi-parameter testing device under a continuous temperature change field, and obtaining the left and right pigtail lengths L1 and L2 of the ring and the standard refractive index distribution n0 corresponding to the pigtail, as well as the corresponding temperature and thermal strain change data during the test;

[0013] Step 2 (102): Decouple the measured temperature and thermal strain change data to calculate the refractive index change α T ;

[0014] Step 3 (103): The refractive index change α obtained by decoupling calculation in step 2 (102) T , the zero drift prediction result Z0 of the optical fiber sensitive ring (501) with temperature change under full temperature test can be obtained, and the corresponding zero drift optimization target Z1 can be set at the same time;

[0015] Step 4 (104): Determine a temperature point, adjust the right pigtail length L2 of the optical fiber sensitive ring (501), and fit the refractive index change α T , the relationship between zero drift and the change of right pigtail length;

[0016] Step five (105): observe whether the fitting curve between the zero drift of the optical fiber sensitive ring (501) and the change in the length of the right pigtail thereof passes through the zero point;

[0017] Step 6 (106): If the answer of step 5 (105) is yes, the optimal optimization direction and length L of the tail fiber required for adjusting the zero drift optimization of the optical fiber sensitive ring (501) at this temperature point can be determined. min ;

[0018] Step 7 (107): If the judgment of step 5 (105) is no, then adjust the left pigtail length L1 of the optical fiber sensitive ring to fit the refractive index change α T , the relationship between zero drift and the change in the length of the left pigtail, and then returns to step five (105);

[0019] Step 8 (108): Repeat steps 4 (104) to 7 (107) to calculate the best optimization direction of adjusting the fiber pigtail by the fiber sensitive ring (501) at other temperature points in the test and the fiber pigtail length L. min ;

[0020] Step nine (109): Count the best optimization directions of adjusting the pigtail at all temperature points, and determine the final optimization direction according to the same direction of the most temperature points;

[0021] Step 10 (110): Calculate the average value L of the optimized pigtail length at each temperature point m As the final adjustment length;

[0022] Step 11 (111): Compare the optimal length L of the pigtail m / n0 and the length of the pigtail corresponding to the optimization direction, and determining the method for optimizing the pigtail of the final optical fiber sensitive ring (501);

[0023] 2. A method for optimizing thermally induced zero drift range of an optical fiber gyroscope with quantitative control of pigtail length according to claim 1, characterized in that the polarization-maintaining OFDR multi-parameter measurement device in step 1 (101) comprises a light source (10), a 45-degree polarizer (101), a first polarization-maintaining coupler (102), an auxiliary interferometer module (20), a main interferometer module (30), a data acquisition and processing module (40), an optical fiber sensitive ring (501) and a temperature box (502); the continuous frequency-sweeping light emitted by the light source 10 first passes through the 45-degree polarizer (101) to adjust the polarization state of the injected light to 45°, and then is divided into two beams through the first polarization-maintaining coupler (102); 1% of the optical signal is injected into the auxiliary interferometer module (20) to generate an auxiliary interference signal for eliminating the phase noise of the beat frequency signal output by the main interferometer module (30); and 99% of the optical signal is injected into the main interferometer module (30), and then is divided into two beams through the second polarization-maintaining coupler (301), 1% of the optical signal is injected into the reference arm, and 99% of the optical signal is injected into the measurement arm where the polarization-maintaining circulator (302) is located, and then enters the optical fiber sensitive ring (501) to be optimized through the polarization-maintaining circulator 302, and the reflected signal light passes through the polarization-maintaining circulator (302) again and then merges into the optical fiber sensitive ring (501); the main interference signal passes through the first and second polarization beam splitters (304) and (306), and then enters the first photoelectric balanced detector (305) and the second photoelectric balanced detector (307) respectively to convert the optical signal into an electrical signal, and finally the auxiliary interference signal and the main interference signal are respectively collected through the acquisition card (401) in the data acquisition and processing module (40), and the data is transmitted to the computer terminal (402);

[0024] 3. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length according to claim 1, characterized in that the zero drift prediction result Z0(i) of the optical fiber sensitive ring (501) changing with temperature under the full temperature test in step three (103) and the corresponding zero drift optimization value Z2(i) are set, i is the i-th temperature point, i=1,2,3...N, N is the total number of temperature points;

[0025] 4. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length according to claim 1, characterized in that in the step five (105), it is determined whether the fitting curve passes through a zero point, where the zero point refers to the right pigtail length corresponding to the zero drift being 0 at the temperature point;

[0026] 5. The method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length according to claim 1, characterized in that in the step 11 (111), by comparing the optimal optimized pigtail length L mThe size between / n0 and the length of the pigtail corresponding to the optimization direction determines the final method for optimizing the pigtail of the optical fiber sensitive ring (501). When the optimal optimization length L of the pigtail is m / n0 is greater than the length of the pigtail in the corresponding optimized direction, then the pigtail length is L in the opposite direction by lengthening the pigtail. m / n0 optical fiber to adjust the geometric symmetry and complete the zero drift optimization of the ring; otherwise, the method of cutting the pigtail is used to cut the pigtail length L in the corresponding direction. m / n0 optical fiber is used to adjust the geometric symmetry and complete the zero drift optimization of the ring.

[0027] Refractive index change α under thermal strain T The expression is:

[0028] (1)

[0029] Where n0 is the standard refractive index, p 11 、p 12 is the photoelastic coefficient, ε θ is the axial thermal strain, n T is the thermo-optical coefficient of the optical fiber.

[0030] The CW light of the fiber sensitive ring is disturbed by the external temperature at point s, which causes a change in the refractive index and leads to a positive phase difference. Similarly, the CCW light will also have a change in the refractive index at Ls, but a negative phase difference will be generated. Therefore, the two beams produce different refractive index changes on the symmetrical length, which is called the asymmetric distribution of refractive index α Ts . Asymmetric distribution of refractive index α Ts The expression is as follows:

[0031] (2)

[0032] Asymmetric distribution of refractive index α Ts The relationship between and thermal drift is expressed as follows:

[0033] (3)

[0034] Compared with the existing optimization method, the advantages of the present invention are:

[0035] The present invention proposes a method for optimizing the zero drift extreme error of a fiber optic gyroscope based on quantitative pigtail length control. Compared with the traditional qualitative pigtail length adjustment method, it achieves an improvement from qualitative to quantitative and significantly improves the optimization accuracy.

[0036] The optimization method proposed by the present invention can achieve the best optimization of the zero drift performance of the optical fiber sensitive ring by only performing one correction operation on the pigtail.

[0037] The optimization method proposed in the present invention can accurately correct the length of the pigtail, is applicable to all temperature points, and can optimize the full-temperature zero-drift range of the optical fiber sensitive ring.

[0038] The optimization method proposed in the present invention has simple process, can effectively correct the geometric symmetry of the optical fiber ring, improve its zero drift performance, and can be widely promoted and applied to the development of high-precision gyro systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the device design of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0040] Figure 1 The present invention is a flow chart of a method for optimizing the thermally induced zero drift range of a fiber optic gyroscope by quantitatively controlling the length of a pigtail fiber;

[0041] Figure 2 This is a diagram of the device for polarization-maintaining OFDR multi-parameter testing;

[0042] Figure 3 It is a graph of the temperature rate change over time in the full temperature test;

[0043] Figure 4 is the refractive index change α T Graphs that vary with fiber length;

[0044] Figure 5 is the refractive index change α T Curve diagram of the change in the length of the pigtail cut on the right side of the optical fiber sensitive ring;

[0045] Figure 6 This is a curve showing the change in zero drift with the cutting length of the fiber pigtail on the right side of the optical fiber sensitive ring. DETAILED DESCRIPTION

[0046] In order to more clearly explain the application objectives, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with embodiments and drawings, but the protection scope of the present invention should not be limited thereby. Specific embodiment 1

[0048] A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of the pigtail length, the specific operation steps are as follows:

[0049] In the first step, the optical fiber sensitive ring 501 is placed in a temperature box 502, and the optical fiber sensitive ring is tested by a polarization-maintaining OFDR multi-parameter test device under a continuous temperature change field, and the left and right pigtail lengths L1 and L2 of the ring and the standard refractive index distribution n0 corresponding to the pigtail are obtained, as well as the corresponding temperature and thermal strain change data in the test;

[0050] like Figure 2 The figure shows the polarization-maintaining OFDR multi-parameter test device used in the first step. The selection of the main optoelectronic devices and their parameters in the device are as follows:

[0051] The light source 10 is a narrow linewidth tunable laser source, the linewidth of the light source is 70kHz, the set wavelength tuning range is 1545nm~1555nm, the sweep rate is 10nm / s, and the sweep time is 1s.

[0052] The maximum detection bandwidth of the first balanced photodetector 305 and the second balanced photodetector 307 are both 80 MHz, the peak-to-peak value VP-P of the electrical noise in the time domain is less than 30 mV, and the conversion gain is 4×10 4 V / W.

[0053] The sampling rate of acquisition card 401 is set to 180MHz / s, its effective number of bits after compensation is 8.6 bits, the spurious-free dynamic range is 67.4 dB, and the no-load electrical noise is VP-P=2.8 mV.

[0054] The first coupler 102, the second coupler 301 and the third coupler 303 are all polarization-maintaining couplers. The splitting ratios of the first polarization-maintaining coupler 101 and the second polarization-maintaining coupler 301 are both 99:1, and the splitting ratio of the third polarization-maintaining coupler 303 is 50:50.

[0055] The auxiliary interferometer module 20 adopts a Michelson interferometer, and the refractive index of the single-mode optical fiber used is 1.456.

[0056] The optical fiber sensitive ring 501 to be optimized is wound with panda-type polarization-maintaining optical fiber.

[0057] In the full temperature test of the optical fiber sensitive ring, the temperature change rate of the temperature box 502 is set as follows: Figure 3 As shown in the figure, the specific process is: first keep the temperature at 25℃ for 20 minutes; then cool down to -45℃ at a temperature change rate of 1℃ / min, and it takes 70 minutes to cool down; then keep the temperature at -45℃ for 60 minutes, and then heat up to 70℃ at a temperature change rate of 1℃ / min, and it takes 115 minutes to heat up; finally keep the temperature at 70℃ for 60 minutes, and the full temperature test is over. From the beginning of the full temperature test, every 5℃ is a temperature point.

[0058] In the first step, the specific implementation method of testing the optical fiber sensitive ring by using the polarization-maintaining OFDR multi-parameter testing device is as follows: placing the optical fiber sensitive ring 501 in the temperature box 502 and setting a complete temperature change curve. The continuously swept frequency light emitted by the light source 10 will first pass through the 45° polarizer 101 to adjust the polarization state of the injected light to 45°, and then be divided into two beams through the first polarization-maintaining coupler 101, 1% of the light signal is injected into the auxiliary interferometer module 20 to generate an auxiliary interference signal for eliminating the phase noise of the beat signal output by the main interferometer module 30; in addition, 99% of the light signal is injected into the main interferometer module 30; then the polarized light is divided into two beams through the second polarization-maintaining coupler 301, and 1% of the light signal is injected into the reference arm; 99% of the light signal is injected into the measuring arm where the polarization-maintaining circulator 302 is located, and then enters the optical fiber sensitive ring 501 to be optimized through the polarization-maintaining circulator 302, and the reflected signal light passes through the polarization-maintaining circulator 302 again and then merges; after the main interference signal passes through the polarization beam splitters 304 and 306 respectively, the beat signal is separated and enters the first photoelectric balanced detector 305 and the second photoelectric balanced detector 307 respectively to convert the light signal into an electrical signal. The auxiliary interference signal and the main interference signal generated by the main interferometer module 30 are respectively collected by the acquisition card 401 in the data acquisition and processing module 40, and the data are transmitted to the computer terminal 402 for storage.

[0059] The second step is to decouple the measured temperature and thermal strain change data to calculate the refractive index change α T , refractive index change α T The calculation formula is:

[0060]

[0061] Refractive index change α T As the length of the optical fiber changes Figure 4 shown.

[0062] The third step is to calculate the refractive index change α obtained by decoupling in the second step. T , we can get the asymmetric distribution of refractive index α Ts , the expression is:

[0063]

[0064] Through the uneven distribution of refractive index α Ts The relationship between and thermal drift is expressed as:

[0065]

[0066] In this way, the zero drift prediction result Z0 of the optical fiber sensitive ring with temperature change under full temperature test can be obtained, and the corresponding zero drift optimization target Z1 can be set at the same time.

[0067] The fourth step is to determine the initial temperature point, adjust the right tail fiber length of the optical fiber sensitive ring, and fit the refractive index change α T , the relationship between zero drift and the change in the length of the right pigtail, such as Figure 5 and 6 shown.

[0068] The fifth step is to observe that the fitting curve between the zero drift of the optical fiber ring and the change in the length of its right pigtail passes through the zero point. The best optimization point corresponds to a cut right pigtail length of approximately 7.6 m.

[0069] Step 6: Calculate the optimal optimization direction of the fiber optic sensitive ring to adjust the pigtail and the pigtail length L at other temperature points in the full temperature test. min ;

[0070] Step 7: Count the best optimization directions for adjusting the pigtails at all temperature points, and determine the final optimization direction based on the same direction at most temperature points.

[0071] Step 8: Calculate the average value L of the optimized pigtail length at each temperature point m As a final adjustment length.

[0072] The ninth step is to calculate the best optimized length of the pigtail, which is smaller than the pigtail length in the corresponding optimization direction. Therefore, the best optimization point can be reached by cutting the right pigtail to adjust the geometric symmetry and thus complete the zero drift optimization of the fiber optic gyroscope.

[0073] The above embodiments describe in detail some implementation methods of the method for optimizing the thermally induced zero drift extreme difference of an optical fiber gyroscope with quantitative control of the pigtail length proposed by the present invention. However, for those skilled in the art, various modifications and variations can be made to the above specific embodiments without departing from the principles of the present invention, and various technical features and structures proposed by the present invention can be combined in different ways, but they do not exceed the protection scope of the present invention, and these should all be regarded as the protection scope of the present invention.

Claims

1. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of pigtail length, characterized in that: Based on the principle that adjusting the pigtails on different sides of the optical fiber ring and the corresponding length can optimize its zero drift, the optimal pigtail length is determined by the relationship between zero drift and the change in the pigtail length on different sides of the optical fiber ring. Then, the pigtail on the corresponding side is cut or lengthened to the optimal pigtail length to adjust the geometric symmetry of the ring and optimize the zero drift of the optical fiber sensitive ring. The specific steps are as follows: Step 1 (101): placing the optical fiber sensitive ring (501) in a temperature box (502), testing the optical fiber sensitive ring (501) by using a polarization-maintaining OFDR multi-parameter testing device under a continuous temperature change field, and obtaining the left and right pigtail lengths L1 and L2 of the ring and the standard refractive index distribution n0 corresponding to the pigtail, as well as the corresponding temperature and thermal strain change data during the test; Step 2 (102): Decouple the measured temperature and thermal strain change data to calculate the refractive index change α T ; Step 3 (103): The refractive index change α obtained by decoupling calculation in step 2 (102) T , the zero drift prediction result Z0 of the optical fiber sensitive ring (501) with temperature change under full temperature test can be obtained, and the corresponding zero drift optimization target Z1 can be set at the same time; Step 4 (104): Determine a temperature point, adjust the right pigtail length L2 of the optical fiber sensitive ring (501), and fit the refractive index change α T , the relationship between zero drift and the change of right pigtail length; Step five (105): observe whether the fitting curve between the zero drift of the optical fiber sensitive ring (501) and the change in the length of the right pigtail thereof passes through the zero point; Step 6 (106): If the answer of step 5 (105) is yes, the optimal optimization direction and length L of the tail fiber required for adjusting the zero drift optimization of the optical fiber sensitive ring (501) at this temperature point can be determined. min ; Step 7 (107): If the judgment of step 5 (105) is no, then adjust the left pigtail length L1 of the optical fiber sensitive ring to fit the refractive index change α T , the relationship between zero drift and the change in the length of the left pigtail, and then returns to step five (105); Step 8 (108): Repeat steps 4 (104) to 7 (107) to calculate the best optimization direction of adjusting the fiber tail by the optical fiber sensitive ring (501) at other temperature points in the test and the fiber tail length L. min ; Step nine (109): Count the best optimization directions of adjusting the pigtail at all temperature points, and determine the final optimization direction according to the same direction of the most temperature points; Step 10 (110): Calculate the average value L of the optimized pigtail length at each temperature point m As the final adjustment length; Step 11 (111): Compare the optimal length L of the pigtail m / n0 and the length of the pigtail corresponding to the optimization direction, and determine the method for optimizing the pigtail of the final optical fiber sensitive ring (501).

2. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of pigtail length according to claim 1, characterized in that: The polarization-maintaining OFDR multi-parameter measurement device in step 1 (101) comprises a light source (10), a 45-degree polarizer (101), a first polarization-maintaining coupler (102), an auxiliary interferometer module (20), a main interferometer module (30), a data acquisition and processing module (40), an optical fiber sensitive ring (501) and a temperature box (502). The continuously swept light emitted by the light source 10 first passes through the 45-degree polarizer (101) to adjust the polarization state of the injected light to 45 degrees, and then is divided into two beams through the first polarization-maintaining coupler (102). 1% of the light signal is injected into the auxiliary interferometer module (20) to generate an auxiliary interference signal for eliminating the phase noise of the beat frequency signal output by the main interferometer module (30); and 99% of the light signal is injected into the main interferometer module (30). Afterwards, the optical signal is split into two beams through a second polarization-maintaining coupler (301), 1% of the optical signal is injected into the reference arm, and 99% of the optical signal is injected into the measurement arm where the polarization-maintaining circulator (302) is located, and then enters the optical fiber sensitive ring (501) to be optimized through the polarization-maintaining circulator 302, and the reflected signal light is merged into the optical fiber sensitive ring (501) after passing through the polarization-maintaining circulator (302) again; the main interference signal passes through the first and second polarization beam splitters (304) and (306) respectively, and enters the first photoelectric balanced detector (305) and the second photoelectric balanced detector (307) respectively to convert the optical signal into an electrical signal, and finally the auxiliary interference signal and the main interference signal are respectively collected through the collection card (401) in the data collection and processing module (40), and the data is transmitted to the computer terminal (402).

3. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of pigtail length according to claim 1, characterized in that: The zero drift prediction result Z0(i) of the optical fiber sensitive ring (501) with temperature change under the full temperature test in step three (103) and the set corresponding zero drift optimization value Z2(i), i is the i-th temperature point, i=1,2,3...N, N is the total number of temperature points.

4. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of pigtail length according to claim 1, characterized in that: In step five (105), it is determined whether the fitting curve passes through the zero point, where the zero point refers to the right pigtail length corresponding to the zero drift being 0 at the temperature point.

5. A method for optimizing the thermally induced zero drift range of an optical fiber gyroscope with quantitative control of pigtail length according to claim 1, characterized in that: In step 11 (111), by comparing the optimal optimized length L of the pigtail m / n0 and the size between the length of the pigtail corresponding to the optimization direction, determine the final method for optimizing the pigtail of the optical fiber sensitive ring (501), when the optimal optimization length of the pigtail L m / n0 is greater than the length of the pigtail in the corresponding optimized direction, then the pigtail length is L in the opposite direction by lengthening the pigtail. m / n0 optical fiber to adjust the geometric symmetry and complete the zero drift optimization of the ring; otherwise, the method of cutting the pigtail is used to cut the pigtail length L in the corresponding direction. m / n0 optical fiber is used to adjust the geometric symmetry and complete the zero drift optimization of the ring.

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