Optical fiber ring SHUPE error evaluation and inhibition method based on distributed circumferential strain

Abstract

The invention belongs to the technical field of fiber-optic gyroscopes, and particularly relates to a fiber-optic ring SHUPE error evaluation and inhibition method based on distributed circumferential strain. According to the method, the corresponding relation with the SHUPE error of the optical fiber ring can be established by testing the constant-temperature distributed circumferential strain of the optical fiber ring, the evaluation of the variable-temperature performance of the optical fiber ring is realized, SHUPE error suppression can be carried out in the forward design stage of the optical fiber ring according to the geometric parameters of each component of the optical fiber ring and the material parameters under different temperature point conditions, and the evaluation of the variable-temperature performance of the optical fiber ring is realized. Therefore, the variable-temperature performance of the optical fiber ring is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber optic gyroscopes, and in particular relates to a fiber optic ring SHUPE error evaluation and suppression method based on distributed circumferential strain. Background Art

[0002] The fiber ring is the sensitive core component of the fiber optic gyroscope. In principle, the performance of the fiber ring determines the performance of the fiber optic gyroscope. Since the application scenarios of the fiber optic gyroscope involve variable temperature environments, the performance of the fiber ring in variable temperature environments is particularly important. The working principle of the fiber ring is based on the Sagnac effect. Limited by its own structure, fiber material, and manufacturing process, when the environmental field changes, the internal characteristics of the sensitive fiber also change, and finally introduce non-reciprocal phase difference, affecting the accuracy of the fiber optic gyroscope. This asymmetric temperature disturbance will cause the fiber ring to produce non-reciprocal phase shift, namely "SHUPE error". In fact, the "SHUPE error" in the fiber ring is not comprehensive. The thermal strain and stress generated by temperature can also affect the refractive index of the fiber core according to the photoelastic effect, resulting in thermally induced non-reciprocal error (SHUPE error), which is the same as the strain and stress mechanism of stress-type polarization-maintaining fiber, and has become an important factor limiting the high-precision application of fiber optic gyroscopes.

[0003] For example, a fiber optic ring bonding performance evaluation method based on Brillouin time-domain stress analysis as recorded in CN202311812700.6 only considers process improvement from the perspective of fiber optic ring bonding, and does not establish the relationship between fiber optic ring strain and SHUPE error; a method for testing the temperature distribution of a fiber optic ring in a fiber optic gyroscope as recorded in CN201811116125.5 does not actually use the strain curve for fiber optic ring performance evaluation; a fiber optic gyroscope temperature compensation method as recorded in CN201811237609.5, the compensation scheme for the variable temperature zero bias error can only be compensated by algorithm through variable temperature testing after the fiber optic ring is connected to the fiber optic gyroscope system. Summary of the invention

[0004] Technical problem solved by the present invention: The present invention proposes a quantitative evaluation and suppression method for thermally induced bias error (SHUPE error) which mainly affects the performance of gyroscopes. The distributed circumferential strain of the optical fiber ring is measured at a specific temperature point, and the bias error can be obtained through model calculation. Based on the established model, the influence of different material properties on the bias error can be studied. Then, by analyzing and optimizing the material properties, the SHUPE error can be suppressed.

[0005] The technical solution of the present invention:

[0006] A method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain, the method comprising the following steps:

[0007] Step 1: Calculate the total length L of the sensitive optical fiber of the optical fiber ring, the length of each layer of the sensitive optical fiber, and the outer diameter according to the number of layers, number of turns, inner radius of the optical fiber ring and the size parameters of the optical fiber used;

[0008] Step 2: Use BOTDA to test the distributed circumferential strain of the fiber ring at different temperature points. After baseline calibration and subtraction of strain curves at adjacent temperature points, the circumferential distributed strain difference per unit temperature Δα is obtained. T (z);

[0009] Step 3: Take each layer of optical fiber as a microelement segment δz m , considering the constant slope temperature change condition Calculate the phase difference δφ between adjacent layers Tdot (z m );

[0010] Step 4: Phase difference δφ between adjacent layers Tdot (z m ) solve the zero bias error of adjacent layers; the fiber optic gyroscope SHUPE error ΔΩ generated by the final fiber ring is equal to the accumulated value of the zero bias error of each adjacent layer of optical fiber;

[0011] Step 5: Calculate the circumferential distributed strain difference Δα per unit temperature T (z) According to steps 3 and 4, the SHUPE error is calculated, and the corresponding relationship between the strain difference and the SHUPE error is established, and then the SHUPE error is suppressed by changing the material properties.

[0012] Furthermore, in step 1,

[0013] The radius Ri of the i-th layer of sensitive optical fiber is calculated by the following formula:

[0014]

[0015] The length of the i-th layer of sensitive optical fiber is: L i =2π×R i ×M layer , M layer The number of turns corresponding to each layer of the fiber ring

[0016] N coil The sum of the lengths of the layers of sensitive optical fibers is recorded as the total length L of the sensitive optical fibers of the optical fiber ring.

[0017] Furthermore, in step 2,

[0018] The change of the center frequency of BOTDA Δν B It is proportional to the temperature change ΔT and strain change Δε of the optical fiber, and the following linear correlation is established: Δν B =c 12ΔT+c 11 Δε

[0019] Among them, c 11 The gauge factor representing the frequency shift is expressed in MHz / με; c 12 Represents temperature coefficient, unit is MHz / ℃;

[0020] The distributed circumferential strains at adjacent temperature points are subtracted and then divided by the difference between the temperature points to obtain the strain difference curve under unit temperature change, and then the strain difference slope curve is obtained, and then the strain difference data Δα between adjacent layers at a specific temperature point is obtained. T .

[0021] Furthermore, in step 3,

[0022] according to Calculate the phase difference δφ between adjacent layers Tdot (z m ), where L is the length of the fiber ring, in m; λ is the average wavelength of the optical signal, in m; c is the speed of the optical signal, in m / s; n is the effective refractive index of the optical fiber; Δα T (z m ) is the mth infinitesimal segment δz m The coordinate z m The unit temperature change strain difference of the infinitesimal segment symmetrical about the midpoint.

[0023] Furthermore, in step 4,

[0024] Thermally induced bias error ΔΩ of fiber optic gyroscope generated by fiber ring:

[0025]

[0026] D0 is the average diameter of the sensitive fiber of the fiber ring, δφ is the phase difference δφ of each adjacent layer of fiber Tdot (z m ) and.

[0027] Furthermore, the smaller the thermally induced zero bias error ΔΩ is, the better the performance of the fiber ring is.

[0028] Furthermore, in step 5,

[0029] Establish a model, select the average temperature slope of adjacent layers according to the geometric parameters of each component of the sensitive optical fiber material and the material parameters at different temperature points, calculate the length of each layer of optical fiber as a microelement segment through the radius and number of turns of each layer of the optical fiber ring sensitive optical fiber;

[0030] The circumferential distributed strain difference per unit temperature Δα is calculated T(z) According to steps 3 and 4, the SHUPE error is calculated to determine the influence of each material parameter on the SHUPE error, establish the corresponding relationship between the strain difference and the SHUPE error, and then suppress the SHUPE error by changing the material properties.

[0031] Furthermore, the circumferential distributed strain difference per unit temperature Δα is calculated T (z), specifically:

[0032] The final size parameters of the optical fiber ring are obtained by superimposing the size parameters after radial translation of the optical fiber ring and the size parameters after four-way expansion of the optical fiber ring. The final size parameters at least include: the change in outer diameter of the optical fiber ring Δα T_w and the inner diameter change Δα T_n Combined with the change in the outer diameter of the optical fiber ring Δα T_w and the inner diameter change Δα T_n , obtain the strain difference data between adjacent layers at a single temperature, and then obtain the strain difference data Δα between adjacent layers at all specific temperature points T :

[0033] The beneficial effects of the present invention are as follows:

[0034] The present invention can evaluate the influence of the change of material parameters on the SHUPE error of the optical fiber ring, provide a simple optical fiber ring evaluation method, suppress the SHUPE error, and improve the temperature change performance. By testing the constant temperature distributed circumferential strain of the optical fiber ring, a corresponding relationship with the SHUPE error of the optical fiber ring can be established to realize the evaluation of the temperature change performance of the optical fiber ring, and the SHUPE error can be suppressed in the forward design stage of the optical fiber ring according to the geometric parameters of each component of the optical fiber ring and the material parameters at different temperature points, thereby effectively improving the temperature change performance of the optical fiber ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the SHUPE error evaluation and suppression method of optical fiber ring based on distributed circumferential strain;

[0036] Figure 2 Testing circumferential distributed strain connection device for BOTDA;

[0037] 1-Industrial control computer, 2-BOTDA, 3-Fiber optic patch cord, 4-Fiber optic ring, 5-High and low temperature test chamber

[0038] Figure 3 It is a schematic diagram of the arrangement of sensitive optical fibers inside the optical fiber ring and an enlarged view of the inside of the optical fiber;

[0039] 6-ring adhesive, 7-outer coating, 8-inner coating, 9-optical fiber cladding

[0040] Figure 4 This is the circumferential distributed strain curve of the BOTDA test and the circumferential distributed strain curve at unit temperature obtained after calculation. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described in detail with reference to the accompanying drawings.

[0042] By testing the constant-temperature distributed circumferential strain of the optical fiber ring, the present invention can establish a corresponding relationship with the SHUPE error of the optical fiber ring, realize the evaluation of the temperature-varying performance of the optical fiber ring, and can suppress the SHUPE error in the forward design stage of the optical fiber ring according to the geometric parameters of each component of the optical fiber ring and the material parameters at different temperature points, thereby effectively improving the temperature-varying performance of the optical fiber ring.

[0043] In view of the above analysis, the present invention aims to provide a method for evaluating and suppressing the SHUPE error of an optical fiber ring based on distributed circumferential strain, so as to solve the problem of suppressing the SHUPE error in the forward design of an optical fiber ring.

[0044] A specific embodiment of the present invention discloses a method for evaluating and suppressing SHUPE errors of an optical fiber ring based on distributed circumferential strain, such as Figure 1 As shown, the following steps are included:

[0045] Step 1: Take a certain type of optical fiber ring as an example to calculate. The cladding diameter d1 = 60μm, the inner coating diameter d2 = 80μm, the outer coating diameter (outer diameter) d = 100μm Panda-type polarization-maintaining optical fiber is wound into a ring according to the orthogonal octupole symmetrical winding method. The inner diameter of the optical fiber ring is D = 47.5mm, and the number of layers of the optical fiber ring is N. coil = 40 layers, the number of turns corresponding to each layer of the fiber ring is M layer = 83 turns, the total length of the sensitive optical fiber of the optical fiber ring is calculated to be L = 531.7m, and the radius Ri of the i-th layer of sensitive optical fiber can be calculated by the following formula:

[0046]

[0047] The outer diameter of the fiber ring is D out =R 40 +1 / 2×D, fiber ring height H coil =M layer ×d;

[0048] The length of the i-th layer of sensitive optical fiber is:

[0049] L i =2π×R i ×M layer

[0050] N coilThe sum of the lengths of the layers of sensitive optical fibers is recorded as the total length L of the sensitive optical fibers of the optical fiber ring.

[0051] Step 2: Schematic diagram of the BOTDA test circumferential distributed strain connection device is as follows Figure 2 . Fix the optical fiber ring on the tray with high temperature tape and place it in the high and low temperature test box. Remove 30cm of the optical fiber ring pigtail, mark the A end and the B end respectively, and extend it from the side hole of the high and low temperature test box. The remaining pigtails are coiled into a circle and fixed on the tray with high temperature tape. The high and low temperature test box can control the optical fiber ring to be in a specific temperature environment. Remove 30cm of the optical fiber jumper pigtail and mark the A' end and the B' end respectively. Use a polarization-maintaining fusion splicer to perform polarization-maintaining alignment fusion splicing on the A end and the A' end, and use a polarization-maintaining fusion splicer to perform polarization-maintaining alignment fusion splicing on the B end and the B' end. After fusion, the corresponding interface of the A' end of the optical fiber jumper is connected to the BOTDA pump output connection port (Pump output connector), and the corresponding interface of the B' end of the optical fiber jumper is connected to the BOTDA probe output connection port (Probe output connector). BOTDA is controlled by an industrial control computer through a data line to collect distributed circumferential strain curves.

[0052] The optical fiber jumper is a polarization-maintaining optical fiber in the 1550nm band.

[0053] The micro strain analyzer BOTDA is NBX-6055 (PM) with two optical fiber ports.

[0054] The industrial control computer is connected with the BOTDA via a data line.

[0055] The temperature range of the high and low temperature test box is -70 to +150°C, and the specific temperature points include -45°C, -25°C, -5°C, 15°C, 35°C, 55°C, and 75°C. Each temperature point is kept warm for 50 minutes, and the distributed circumferential strain data of the optical fiber ring is collected starting at 45 minutes.

[0056] Reference Figure 4 ,After the distributed circumferential strain data collection is completed, the data is processed.

[0057] (1) Baseline calibration

[0058] The BOTDA test principle is based on the stimulated Brillouin amplification effect between the pump pulse light (Pump) and the continuous probe light (Probe). By scanning the frequency difference between the two light sources and recording the magnitude of energy transfer along the optical fiber at each frequency difference, the Brillouin gain spectrum along the optical fiber can be obtained. The Brillouin frequency shift distribution along the optical fiber is obtained by performing Lorentz fitting on the Brillouin gain spectrum, thereby realizing fully distributed sensing of optical fiber strain.

[0059] The change of the center frequency of BOTDA Δν B The following linear correlation can be established, which is proportional to the temperature change ΔT and strain change Δε of the optical fiber.

[0060] Δν B =c 12 ΔT+c 11 Δε

[0061] Among them, c 11 The gauge factor representing the frequency shift is expressed in MHz / με; c 12 Represents the temperature coefficient in MHz / ℃. During the test, the instrument will substitute the calibration value for calculation. 11 Usually 0.04970MHz / με, c 12 Usually 1.07000MHz / ℃. During the calibration process, the default value is no strain for the temperature-related c 12 Through baseline alignment, the temperature term can be eliminated, so that the change of strain value can be demodulated.

[0062] The pigtails on both sides of the fiber ring are stress-free fibers, so the strain values ​​of the pigtails on both sides of the fiber ring only change with temperature, and the corresponding strain value is a flat area. Taking the stress-free fibers on both sides of the fiber ring as the benchmark, the baseline of the distributed circumferential strain of the fiber ring at each temperature point can be aligned at the zero strain value to obtain the distributed circumferential strain curve caused by the internal stress state of the fiber ring at each temperature point of the fiber ring.

[0063] (2) Calculation of strain difference slope

[0064] The distributed circumferential strains at adjacent temperature points are subtracted and then divided by the difference between the temperature points to obtain the strain difference curve under unit temperature change. For example, in -45℃, -25℃, -5℃, 15℃, 35℃, 55℃, and 75℃, the strain curve under -45℃ temperature is subtracted from the strain curve under -25℃ temperature, and the difference is divided by the difference between the temperature points (20℃) to obtain the strain difference slope curve, and then the strain difference data Δα between adjacent layers at a specific temperature point is obtained. T .

[0065] Evaluation criteria for the performance of the optical fiber ring: the variance of the strain difference slope at each temperature point should be as close to 0 as possible, the mean value of the strain difference slope should be close to 0, and the overlap of the strain difference curve should be as high as possible;

[0066] A good fiber optic ring requires that the curves of the distributed circumferential strain difference under unit temperature difference completely overlap within the entire operating temperature range, so that the zero bias error of the fiber optic ring in the temperature slope stable area can be constant, thereby optimizing the temperature slope compensability of the variable temperature zero bias.

[0067] Step 3: Take each layer of optical fiber as a microelement segment δz m , considering the constant slope temperature change value The phase difference δφ between adjacent layers of optical fiber is Tdot (z m ) can be calculated according to the formula.

[0068]

[0069] Wherein, L is the total length of the sensitive optical fiber, in m; λ is the average wavelength of the optical signal (in vacuum), in m; c is the speed of the optical signal (in vacuum), in m / s; n is the effective refractive index of the optical fiber; Δα T (z m ) is the mth infinitesimal segment δz m The coordinate z m The unit temperature change strain difference of the infinitesimal segment symmetrical about the midpoint.

[0070] Step 4: Combine the zero bias calculation formula and calculate the phase difference δφ of adjacent optical fibers Tdot (z m ) Solve the bias error of adjacent layers of optical fiber. The thermally induced bias error ΔΩ of the FOG generated by the final fiber ring is equal to the accumulated bias error of each adjacent layer of optical fiber, unit: ° / h / (℃ / min).

[0071]

[0072] D0 is the average diameter of the sensitive fiber of the fiber ring, δφ is the phase difference δφ of each adjacent layer of fiber Tdot (z m ) and.

[0073] The smaller the thermally induced zero bias error ΔΩ, the better the performance of the fiber ring.

[0074] Step 5: Select the constant slope temperature change value based on the geometric parameters of each component of the sensitive optical fiber material and the material parameters at different temperature points The unit is ℃ / s (temperature change per second). The length of each layer of optical fiber is calculated by the radius and number of turns of each layer of the optical fiber ring. Each layer of optical fiber is regarded as a microelement segment, with the unit of m. The model formula is used to calculate the strain difference slope με / ℃ (microstrain per degree Celsius change) of adjacent layers at different temperature points.

[0075] like Figure 3 As shown, the winding method is equivalent to the "hexagonal closed packaging array" of optical fibers, and the gaps are filled with ring glue 6. Assuming that the single optical fibers are closely arranged, the areas and proportions of the cladding 9, the inner coating layer 8, the outer coating layer 7, and the ring glue 6 are respectively:

[0076] Optical fiber cladding (including core): 32.65%

[0077] Inner coating: 25.39%

[0078] External coating: 32.65%

[0079] Ring glue: 9.31%

[0080] Therefore, the volume proportion of each part is: The volume proportion of optical fiber cladding is V f =32.65%; the volume proportion of the inner coating layer is V pi =32.65%; the volume proportion of the outer coating layer is V po =32.65%; Ring glue volume ratio V g =32.65%.

[0081] The material parameters of the optical fiber cladding, inner coating, outer coating and ring glue at the temperature points of -55℃, -35℃, -15℃, 0℃, 20℃, 40℃, 60℃ and 85℃ were obtained. The material parameters include Young's modulus, Poisson's ratio and linear thermal expansion coefficient. The Young's modulus E of the optical fiber cladding, inner coating, outer coating and ring glue at any temperature point was obtained by fitting the tested parameters with full temperature spline interpolation from -55℃ to 85℃. f 、E pi 、E po and E g , and obtain the Poisson's ratio ν of the optical fiber cladding, inner coating, outer coating, and ring adhesive at any temperature point f , ν pi , ν po and ν g , the linear thermal expansion coefficient α of the optical fiber cladding, inner coating, outer coating, and ring adhesive at any temperature point is obtained f , α pi , α po and α g .

[0082] Based on the finite element method, the entire fiber ring is regarded as a composite material with uniform properties, and its mechanical parameters and thermal parameters are homogenized. By considering the fiber ring as a composite material in the micromechanics category, the longitudinal Young's modulus of the fiber ring composite material can be obtained as E c :

[0083] E c =E f V f +E pi V pi +E po Vpo +E g V g

[0084] The transverse Young's modulus of the optical fiber ring composite material is E r :

[0085]

[0086] Where E f 、E pi 、E po and E g Respectively represent the Young's modulus of the cladding, inner coating, outer coating and ring adhesive, V f 、V pi 、V po and V g They represent the volume fractions of the optical fiber cladding, inner coating, outer coating and winding adhesive respectively.

[0087] Longitudinal Poisson's ratio ν of optical fiber ring composite material cr :

[0088] ν cr =V f ν f +V pi ν pi +V po ν po +V g ν g

[0089] Transverse Poisson's ratio ν of optical fiber ring composites cr :

[0090]

[0091] where νf, ν pi , ν po and ν g They represent the Poisson's ratio of the cladding, inner coating, outer coating and winding adhesive respectively.

[0092] Longitudinal linear thermal expansion coefficient α of optical fiber ring composite material c :

[0093]

[0094] Transverse linear thermal expansion coefficient α of optical fiber ring composite material r :

[0095] α r =V f (1+ν f )α f +V pi (1+νpi )α pi +V po (1+ν po )α po

[0096] +V g (1+ν g )α g -(ν f V f +ν pi V pi +ν po V po +ν g V g )α c

[0097] Among them, α f , α pi , α po and α g They represent the linear thermal expansion coefficients of the cladding, inner coating, outer coating and ring adhesive respectively.

[0098] Select a constant slope temperature ramp value The unit is 1 / 60℃ / s. According to the geometric parameters of each component of the sensitive optical fiber material and the material parameters at a specific temperature point, the dimensional parameters of the optical fiber ring after radial translation can be obtained by calculating the longitudinal Young's modulus, the longitudinal Poisson's ratio, and the longitudinal linear thermal expansion coefficient. The dimensional parameters of the optical fiber ring after four-way expansion are obtained by calculating the transverse Young's modulus, the transverse Poisson's ratio, and the transverse linear thermal expansion coefficient. The dimensional parameters of the optical fiber ring after radial translation and the dimensional parameters of the optical fiber ring after four-way expansion are superimposed to obtain the final dimensional parameters of the optical fiber ring. The final dimensional parameters at least include: the change in the outer diameter of the optical fiber ring Δα T_w and the inner diameter change Δα T_n Combined with the change in the outer diameter of the optical fiber ring Δα T_w and the inner diameter change Δα T_n , obtain the strain difference data between adjacent layers at a single temperature, and then obtain the strain difference data Δα between adjacent layers at all specific temperature points T .

[0099]

[0100] According to steps (3) and (4), the thermally induced zero bias error is calculated to determine the influence of each material parameter on the SHUPE error, and then the SHUPE error is suppressed by changing the material properties.

[0101] The present invention can evaluate the influence of the change of material parameters on the SHUPE error of the optical fiber ring, provide a simple optical fiber ring evaluation method, suppress the SHUPE error, and improve the temperature change performance. By testing the constant temperature distributed circumferential strain of the optical fiber ring, a corresponding relationship with the SHUPE error of the optical fiber ring can be established to realize the evaluation of the temperature change performance of the optical fiber ring, and the SHUPE error can be suppressed in the forward design stage of the optical fiber ring according to the geometric parameters of each component of the optical fiber ring and the material parameters at different temperature points, thereby effectively improving the temperature change performance of the optical fiber ring.

Claims

1. A method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain, characterized in that: The method comprises the following steps: Step 1: Calculate the total length L of the sensitive optical fiber of the optical fiber ring, the length of each layer of the sensitive optical fiber, and the outer diameter according to the number of layers, number of turns, inner radius of the optical fiber ring and the size parameters of the optical fiber used; Step 2: Use BOTDA to test the distributed circumferential strain of the fiber ring at different temperature points. After baseline calibration and subtraction of strain curves at adjacent temperature points, the circumferential distributed strain difference per unit temperature Δα is obtained. T (z); Step 3: Take each layer of optical fiber as a microelement segment δz m , considering the constant slope temperature change condition Calculate the phase difference δφ between adjacent layers Tdot (z m ); Step 4: Phase difference δφ between adjacent layers Tdot (z m ) solve the zero bias error of adjacent layers; the fiber optic gyroscope SHUPE error ΔΩ generated by the final fiber ring is equal to the accumulated value of the zero bias error of each adjacent layer of optical fiber; Step 5: Calculate the circumferential distributed strain difference Δα per unit temperature T (z) According to steps 3 and 4, the SHUPE error is calculated, and the corresponding relationship between the strain difference and the SHUPE error is established, and then the SHUPE error is suppressed by changing the material properties.

2. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 1, characterized in that: In step 1, The radius Ri of the i-th layer of sensitive optical fiber is calculated by the following formula: The length of the i-th layer of sensitive optical fiber is: L i =2π×R i ×M layer , M layer The number of turns corresponding to each layer of the fiber ring N coil The sum of the lengths of the layers of sensitive optical fibers is recorded as the total length L of the sensitive optical fibers of the optical fiber ring.

3. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 2, characterized in that: In step 2, The change of the center frequency of BOTDA Δν B It is proportional to the temperature change ΔT and strain change Δε of the optical fiber, and the following linear correlation is established: Δν B =c 12 ΔT+c 11 Δε Among them, c 11 The gauge factor representing the frequency shift is expressed in MHz / με; c 12 Represents temperature coefficient, unit is MHz / ℃; The distributed circumferential strains at adjacent temperature points are subtracted and then divided by the difference between the temperature points to obtain the strain difference curve under unit temperature change, and then the strain difference slope curve is obtained, and then the strain difference data Δα between adjacent layers at a specific temperature point is obtained. T .

4. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 3, characterized in that: In step 3, according to Calculate the phase difference δφ between adjacent layers Tdot (z m ), where L is the length of the fiber ring, in m; λ is the average wavelength of the optical signal, in m; c is the speed of the optical signal, in m / s; n is the effective refractive index of the optical fiber; Δα T (z m ) is the mth infinitesimal segment δz m The coordinate z m The unit temperature change strain difference of the infinitesimal segment symmetrical about the midpoint.

5. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 4, characterized in that: In step 4, Thermally induced bias error ΔΩ of fiber optic gyroscope generated by fiber ring: D0 is the average diameter of the sensitive fiber of the fiber ring, δφ is the phase difference δφ of each adjacent layer of fiber Tdot (z m ) and.

6. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 5, characterized in that: The smaller the thermally induced zero bias error ΔΩ, the better the performance of the fiber ring.

7. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 5, characterized in that: In step 5, Establish a model, select the average temperature slope of adjacent layers according to the geometric parameters of each component of the sensitive optical fiber material and the material parameters at different temperature points, calculate the length of each layer of optical fiber as a microelement segment through the radius and number of turns of each layer of the optical fiber ring sensitive optical fiber; The circumferential distributed strain difference per unit temperature Δα is calculated T (z) According to steps 3 and 4, the SHUPE error is calculated to determine the influence of each material parameter on the SHUPE error, establish the corresponding relationship between the strain difference and the SHUPE error, and then suppress the SHUPE error by changing the material properties.

8. The method for evaluating and suppressing SHUPE error of an optical fiber ring based on distributed circumferential strain according to claim 7, characterized in that: The circumferential distributed strain difference per unit temperature Δα is calculated T (z), specifically: The final size parameters of the optical fiber ring are obtained by superimposing the size parameters after radial translation of the optical fiber ring and the size parameters after four-way expansion of the optical fiber ring. The final size parameters at least include: the change in outer diameter of the optical fiber ring Δα T_w and the inner diameter change Δα T_n Combined with the change in the outer diameter of the optical fiber ring Δα T_w and the inner diameter change Δα T_n , obtain the strain difference data between adjacent layers at a single temperature, and then obtain the strain difference data Δα between adjacent layers at all specific temperature points T :

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