A method for improving the precision of a fiber-optic gyroscope based on double lithium niobate waveguides

Abstract

The application relates to the technical field of navigation, and discloses a method for improving the precision of an optical fiber gyroscope based on double lithium niobate waveguides, which adopts double lithium niobate waveguides to jointly suppress intensity noise of an optical path system; the RIN power spectral density after superposition of two light paths reaches a minimum value when the light intensity of the main light path is consistent with that of the reference light path in a manner that the light power returned to a photoelectric detector of the main light path and the reference light path is consistent; the loss of the optical path system is controlled to match the loss change of a sensitive optical fiber ring, and the relative intensity suppression effect of the optical path system is stabilized. The method is suitable for different initial losses and environmental changes, and overcomes the defects that the traditional RIN suppression method often adopts fixed parameters or a single compensation means.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of navigation technology, and particularly relates to a method for improving the precision of a fiber-optic gyroscope based on double lithium niobate waveguides. BACKGROUND

[0002] A fiber-optic gyroscope realizes the measurement of angular velocity based on the Sagnac effect, has advantages such as no moving parts, impact resistance, long service life and high precision, and is widely used in fields such as inertial navigation, attitude control and automatic driving.

[0003] In order to improve the precision of the gyroscope, a high-power ASE light source is usually used to suppress the coherent noise in the gyroscope optical path. With the increase of the power of the ASE light source, the relative intensity noise (RIN) generated by the random fluctuation of the light intensity of the light source in the fiber-optic gyroscope becomes the main noise source, and the relative intensity noise generated by the light source must be suppressed in order to further improve the stability of the zero bias of the gyroscope.

[0004] The relative intensity noise (RIN) is derived from the statistical fluctuation of photons and the fluctuation of the power of the light source, and is one of the key factors that limit the precision of the fiber-optic gyroscope, especially the low-frequency noise.

[0005] As shown in Figure 1 , the modulation depth of the gyroscope system is usually increased, and the light power reaching the detector is reduced to reduce the relative intensity noise. However, due to the existence of thermal noise, with the increase of the modulation depth, the total noise presents a V-shaped curve, and the total noise actually increases, and the zero precision of the gyroscope actually decreases. Further increasing the modulation depth cannot further suppress the intensity noise.

[0006] On the other hand, after the modulation depth of the gyroscope system is increased, the Y waveguide, which is the actuator for increasing the modulation depth, has a performance deterioration in the 2π reset error due to its own wave slope at a large modulation depth, resulting in a performance deterioration of the scale factor of the gyroscope at a large modulation depth, especially a decrease in the symmetry of the scale factor.

[0007] Therefore, in order to obtain high gyroscope precision and scale performance, the gyroscope is usually designed to work at point A, at which the modulation depth is not deep, so that the intensity noise cannot be suppressed, and the precision of the gyroscope cannot be improved.

[0008] As shown in Figure 2As shown, in order to further improve the precision of the gyroscope, the relative intensity noise must be suppressed, and the operating point is moved from point A to point B. For high-precision fiber-optic gyroscopes, the length of the fiber coil is limited by the winding process, and there are differences in the fiber coil, resulting in inconsistent fiber coil losses. At the same time, when the fiber coil is affected by the external environment temperature, the fiber coil loss will also change. The change of the fiber coil loss causes the overall loss of the optical path to change, and the relative intensity noise also changes. The relative intensity noise suppression technology of fixing the optical device parameters, such as deepening the modulation depth and fixing it at a certain value, will greatly reduce the effect of relative intensity noise suppression.

[0009] Therefore, in practice, there is an urgent need for a method that can adaptively adjust according to the actual use state to improve the precision of the fiber-optic gyroscope according to the differences of the fiber coil and the different use environments. SUMMARY

[0010] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application provides a method for improving the precision of a fiber-optic gyroscope based on double lithium niobate waveguides.

[0011] A method for improving the precision of a fiber-optic gyroscope based on double lithium niobate waveguides,

[0012] S1, the initial light generated by the light source is divided into two beams, which enter the main light path and the reference light path respectively. The light entering the main light path passes through the first waveguide and a sensitive fiber coil in turn, forming a main light path signal carrying angular rate information and light source intensity noise. The light entering the reference light path passes through the second waveguide, forming a reference light path signal carrying light source intensity noise;

[0013] S2, the main light path signal and the reference light path signal are combined to generate a detection signal representing the optical power of the two signals;

[0014] S3, based on the detection signal, the optical power of the main light path signal and / or the reference light path signal is adjusted by dynamically adjusting the first waveguide and / or the second waveguide, until the optical power of the main light path signal and the reference light path signal is consistent, thereby suppressing the light source intensity noise;

[0015] The second waveguide is adjusted to compensate for the loss difference of the main light path caused by different gyroscope models.

[0016] Further, the second waveguide is a lithium niobate straight waveguide, and the second waveguide is adjusted under the control of a controller.

[0017] Further, the first waveguide is adjusted to compensate for the change of the optical path loss of the main light path caused by the change of the environmental temperature;

[0018] The first waveguide is a lithium niobate Y waveguide, and the first waveguide is adjusted under the control of a controller.

[0019] Further, the step of adjusting the first waveguide comprises:

[0020] An ambient temperature of the sensitive fiber ring is measured to obtain temperature data.

[0021] According to a preset temperature-optical path loss model and the temperature data, a drift amount of the main optical path light power is determined.

[0022] Based on the drift amount, the controller generates a compensation voltage and applies the compensation voltage to the first waveguide to stabilize the optical power of the main optical path signal.

[0023] Further, the S1 step further comprises:

[0024] The reference optical path further comprises a rotating mirror, and the reference optical path light is reflected by the rotating mirror after passing through the second waveguide and passes through the second waveguide again.

[0025] Further, the rotating mirror is a 45° Faraday rotating mirror, which rotates the polarization direction of the input light by 90° to output, and realizes fast and slow axis conversion.

[0026] Further, the ambient temperature of the sensitive fiber ring is measured by a temperature sensor, which is used to measure the ambient temperature of the sensitive fiber ring and output temperature data to the controller.

[0027] The controller outputs a control signal to the lithium niobate Y waveguide based on the temperature data to compensate for the change of the optical path loss of the main optical path caused by the temperature change.

[0028] Further, the S1 step further comprises:

[0029] A wide-spectrum light is generated by an ASE light source, and the wide-spectrum light is divided into main optical path light and reference optical path light by a polarization maintaining fiber beam splitter, and is transmitted to the main optical path and the reference optical path, respectively, wherein the polarization maintaining fiber beam splitter comprises a fiber polarizer and a 50:50 half-transmission half-reflection film to improve the extinction ratio and realize optical path distribution; the 50:50 half-transmission half-reflection film ensures that the incident light of the ASE light source does not directly enter the photodetector, and realizes the optical path connection of the main optical path and the reference optical path.

[0030] Further, the main optical path signal and the reference optical path signal are received by a photodetector.

[0031] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0032] Meanwhile, the lithium niobate Y waveguide and the lithium niobate straight waveguide are used to dynamically adjust the optical power of the main light path and the reference light path, so that different initial losses and environmental changes are adapted, and the defects that the traditional RIN suppression method often uses fixed parameters or a single compensation method are overcome. Compared with the method of suppressing RIN by deepening the modulation depth, the scheme can theoretically avoid the problems of thermal noise limitation and scale factor deterioration in the traditional method by introducing the reference light path for noise cancellation and assisting the optimization of the modulation depth.

[0033] According to the temperature change, the Y waveguide voltage is adjusted in real time to stabilize the optical power of the main light path, and the straight waveguide parameters are adjusted according to different gyro models (different fiber lengths) to match the initial loss, so that the scheme has strong engineering practicability and adaptability. Compared with the RIN suppression technology with fixed parameters, the dynamic adjustment of the double waveguide can better adapt to the change of the optical path loss, so that the stable suppression effect is maintained.

[0034] The technical scheme is based on the existing fiber optic gyroscope RIN suppression technology, and by means of the innovative double lithium niobate waveguide structure and dynamic compensation strategy, a more adaptive and potentially better performance solution is provided, which has high creativity.

[0035] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present application or in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0037] Figure 1 is a traditional noise and modulation depth relationship curve of fiber optic gyroscope;

[0038] Figure 2 is a fiber optic gyroscope noise curve after relative intensity noise suppression;

[0039] Figure 3 is a double lithium niobate waveguide high-precision fiber optic gyroscope light path structure diagram proposed by the present application;

[0040] Figure 4 is a polarization maintaining optical fiber beam splitter structure adopted by the present application;

[0041] Figure 5 is a typical fiber ring loss and temperature relationship curve of the present application;

[0042] Figure 6It is a suppression effect comparison chart of the high-precision fiber-optic gyroscope of the double-lithium niobate waveguide of the application. DETAILED DESCRIPTION

[0043] To make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0044] The present application aims to solve the problem that the high-precision fiber-optic gyroscope cannot improve the gyroscope precision due to the existence of relative intensity noise in the optical system caused by using a high-power ASE light source. Therefore, the present application proposes the following scheme: using double-lithium niobate waveguide to jointly suppress the intensity noise of the optical system; controlling the loss of the optical system to match the loss change of the sensitive fiber ring, and stabilizing the relative intensity suppression effect of the optical system.

[0045] As shown in Figure 3 , the optical path structure of the high-precision fiber-optic gyroscope of the double-lithium niobate waveguide proposed by the present application is shown.

[0046] The scheme uses a double-lithium niobate waveguide structure, which includes a main optical path and a reference optical path.

[0047] Main optical path: ASE light source-polarization maintaining fiber beam splitter-lithium niobate Y waveguide-sensitive fiber ring-lithium niobate Y waveguide-polarization maintaining fiber beam splitter-optoelectronic detector. This optical path is used for sensing the angular rate.

[0048] Reference optical path: ASE light source-polarization maintaining fiber beam splitter-lithium niobate straight waveguide-rotary mirror-lithium niobate straight waveguide-polarization maintaining fiber beam splitter-optoelectronic detector. This optical path returns part of the RIN of the light source.

[0049] RIN suppression: by making the optical power returned to the optoelectronic detector consistent between the signal optical path and the reference optical path, the RIN power spectral density after the superposition of the two optical paths can theoretically reach a minimum value of 0 under certain conditions (B=1, i.e., the light intensity of the signal light and the reference light is consistent).

[0050] Dynamic optical power matching, adjusting the optical power of the reference light path with a lithium niobate straight waveguide (such as a Mach-Zehnder type electro-optic modulator) to match the initial optical path loss difference caused by different lengths of optical fiber rings or the reflectivity of fixed mirrors; adjusting the optical power of the main light path with a lithium niobate Y waveguide, monitoring the temperature change and adjusting the modulation voltage of the Y waveguide according to the preset temperature-optical path loss model to compensate for the change in optical fiber ring loss caused by changes in ambient temperature, and keeping the signal light path power stable.

[0051] Lithium niobate Y waveguide and lithium niobate straight waveguide for adjusting the optical power of the main light path and the reference light path, respectively.

[0052] Polarization maintaining fiber beam splitter: composed of a fiber polarizer and a 50:50 half-transmission half-reflection film, ensuring the extinction ratio of the signal light path and the reference light path, and realizing the connection of the light path in a specific direction.

[0053] Rotary mirror: a 45° Faraday rotary mirror is used to rotate the input light by 90° and output it, realizing the conversion of fast and slow axes to improve the extraction efficiency of the RIN signal in the reference light path.

[0054] Specifically described as follows:

[0055] 1. Optical path composition and working process

[0056] The method for improving the precision of the fiber optic gyroscope based on the double lithium niobate waveguide optical system is composed of the following devices: ASE light source, polarization maintaining fiber beam splitter, lithium niobate Y waveguide, lithium niobate straight waveguide, sensitive optical fiber ring, rotary mirror and photodetector.

[0057] It can be further divided into a main light path and a reference light path. The main light path senses the angular rate input from the outside of the gyroscope, and the reference light path returns a part of the light source relative intensity noise. The reference light path and the main light path are subtracted to suppress the relative intensity noise.

[0058] Main light path composition and signal light transmission process: the light generated by the ASE light source enters the lithium niobate Y waveguide after passing through the polarization maintaining fiber beam splitter. After being split by the lithium niobate Y waveguide, the light enters the sensitive optical fiber ring. The two beams of light propagating in the sensitive optical fiber ring return to the lithium niobate Y waveguide. The lithium niobate Y waveguide and the sensitive optical fiber ring form a Sagnac interferometer, which senses the external angular velocity. The light from the lithium niobate Y waveguide enters the polarization maintaining fiber beam splitter and finally enters the photodetector.

[0059] Reference light path composition and reference light transmission process: the light generated by the ASE light source enters the lithium niobate straight waveguide after passing through the polarization maintaining fiber beam splitter, enters the rotary mirror, is reflected again after passing through the lithium niobate straight waveguide, enters the polarization maintaining fiber beam splitter, and finally enters the photodetector.

[0060] It is particularly necessary to point out that the polarization maintaining fiber beam splitter is composed of a fiber polarizer and a 50:50 half-transmission half-reflection film, as shown in the figure, the ASE light source is connected to the 1 end, the lithium niobate Y waveguide is connected to the 2 end, the lithium niobate straight waveguide is connected to the 3 end, and the photodetector is connected to the 4 end. Figure 4

[0061] The polarizer is used to improve the extinction ratio of the signal light path and the reference light path; the half-transmission half-reflection film ensures that the incident light at the 1 end cannot enter the 4 end detector, and from the 4 port, the 3 port is the reflection light end of the incident light, and the 2 port is the transmission light end, which ensures the intercommunication of the 3 port and the 4 port, and the 2 port and the 3 port, thereby ensuring the connection of the aforementioned signal light path and reference light path.

[0062] The rotating mirror is composed of a 45° Faraday selective mirror, which rotates by 45°, so that the light input into the rotating mirror is finally rotated by 90° and output, that is, the light input into the rotating mirror from the fast axis becomes the slow axis after entering the rotating mirror.

[0063] The lithium niobate straight waveguide is designed by a lithium niobate thin film waveguide, which mainly utilizes the high refractive index difference between lithium niobate and the surrounding material to realize the restriction of light waves, has low polarization correlation, but the lithium niobate thin film waveguide has high light intensity modulation efficiency.

[0064] The principle of the scheme adopted by the application for suppressing relative intensity noise is as follows:

[0065] The relative intensity noise power spectral density can be expressed as:

[0066] (1)

[0067] In the formula: is the input intensity noise of the light source, B is the ratio of the signal light intensity and the reference light intensity, is the light frequency, and t is the time, in seconds.

[0068] As can be seen from the formula, the phase intensity noise of the two lights after superposition with the polarization direction perpendicular to the signal light and the reference light has a periodic oscillation of cosine type compared with before. And when

[0069] (2)

[0070] The relative intensity noise power spectral density after superposition reaches a minimum value, and when B=1, that is, the signal light and the reference light have the same intensity and power, the relative intensity noise after superposition of the two lights is zero at the minimum value; In the formula, n is a natural number, and the value is 1, 2, 3, ….

[0071] ​Therefore, ensuring that the optical powers of the signal light and the reference light returned to the photodetection are consistent, the relative intensity noise of the fiber-optic gyroscope optical path system is minimized.

[0072] On the one hand, when the fiber-optic gyroscope optical path system, especially the sensitive fiber coil, is subjected to changes in the external environment temperature, the optical path loss thereof changes, leading to changes in the signal light path loss and the signal light power. Therefore, in order to ensure that the optical powers of the reference light path and the signal light path are consistent, the optical power of the signal light path or the optical power of the reference light path needs to be adjusted accordingly.

[0073] On the other hand, due to the different lengths of the sensitive coils of high-precision fiber-optic gyroscopes of different precisions, or the different lengths of the sensitive coils of high-precision fiber-optic gyroscopes of the same precision caused by process problems, the losses of the entire high-precision fiber-optic gyroscope optical path system are different, especially the lengths of the fiber coils of high-precision fiber-optic gyroscopes of different precisions can be from 3000 meters to 10000 meters. If the loss of 1000 meters of fiber is 0.5 dB, the optical path loss difference is 3.5 dB, which is very large. If the optical powers of the signal light path and the reference light path are not matched and adjusted, the relative intensity noise suppression has no effect. The traditional matching method is to adjust the reflectivity of the mirror, which requires the production of a series of mirrors with different reflectivities, and the selection of a mirror with an appropriate reflectivity for assembly during optical path assembly. Since the reflectivity of the mirror is fixed, there will be a large matching error when the optical power is matched.

[0074] The present application adjusts the optical powers of the signal light path and the reference light path in real time by adopting double lithium niobate waveguides and jointly controlling the voltages at the two ends of the double lithium niobate waveguides, so that the optical powers of the signal light path and the reference light path are equal, thereby achieving the best intensity noise suppression effect.

[0075] The traditional large modulation depth can deteriorate the scale factor performance. Since the relative intensity noise of the Y waveguide is eliminated by adopting the straight waveguide, the large modulation depth of the Y waveguide is avoided.

[0076] Embodiment 1

[0077] The straight waveguide is used to adjust the system deviation of fiber-optic gyroscopes of different models:

[0078] Two types of fiber-optic gyroscopes with fiber lengths of 3000 meters and 10000 meters are used to calculate the overall optical path loss of the signal light path by setting the modulation depth of the lithium niobate Y waveguide to 2π / 3:

[0079] The gyro signal light path loss of 3000 meters of optical fiber: polarizer 3dB + beam splitter 3dB + lithium niobate Y waveguide 3dB + optical fiber ring 1.5dB + optical path melting point and device loss 6.5dB, the overall optical path loss is 17dB, the overall optical path loss of the detector end after modulation is about 32dB; the increase of 15dB is the loss of the modulation depth of 2π / 3 of the lithium niobate Y waveguide.

[0080] The gyro signal light path loss of 10000 meters of optical fiber: polarizer 3dB + beam splitter 3dB + lithium niobate Y waveguide 3dB + optical fiber ring 5dB + optical path melting point and device loss 6.5dB, the overall optical path loss is 20.5dB, the overall optical path loss of the detector end after modulation is about 35.5dB; the increase of 15dB is the loss of the modulation depth of 2π / 3 of the lithium niobate Y waveguide.

[0081] The required loss value of the lithium niobate straight waveguide in the reference light path is calculated when the reflectivity of the fixed mirror is 5% (13dB).

[0082] 3000 meters: 32dB - polarizer 3dB - beam splitter 3dB - mirror 13dB - optical path melting point and device loss 3dB = 10dB.

[0083] 10000 meters: 35.5dB - polarizer 3dB - beam splitter 3dB - mirror 13dB - optical path melting point and device loss 3dB = 13.5dB.

[0084] When the lithium niobate straight waveguide adopts a Mach-Zehnder type electro-optic modulator, a double lithium niobate crystal symmetric structure is designed, and the refractive index change caused by the voltage applied on the modulator electrode will lead to the change of interference light intensity, that is, the loss value of the reference light path can be changed, which is controlled at 10dB and 13.5dB respectively, so that the optical power of the signal light path and the reference light path is consistent, and the relative intensity noise suppression effect is realized for both types of fiber optic gyroscope.

[0085] Embodiment 2

[0086] The environmental bias of the fiber optic gyroscope system is adjusted by the Y waveguide,

[0087] When the fiber optic gyroscope is in the environment fluctuation, the adjustment depth and bias of the straight waveguide are large, and the Y waveguide is used to adjust the small fluctuation of the environment.

[0088] When the external environment changes, the signal light path loss of the sensitive ring will change, the temperature and light path loss model can be established, the voltage of the lithium niobate Y waveguide is modified to adjust the signal light path optical power, so that the signal light path optical power remains consistent when the temperature changes.

[0089] A typical optical fiber ring loss and temperature relationship curve is shown inFigure 5 As shown, it can be simply fitted as:

[0090] (3)

[0091] In the formula: P is the optical path loss, K is the proportional coefficient, and T is the temperature.

[0092] The relationship between the lithium niobate Y waveguide modulation voltage and the output power is:

[0093] (4)

[0094] In the formula: is the output optical power, is the input lithium niobate Y waveguide optical power, V is the modulation voltage, is the modulation π voltage.

[0095] Solving (3) and (4), we have

[0096] (5)

[0097] As can be seen from formula 5, by measuring the temperature T of the signal light path and adjusting the modulation voltage V of the lithium niobate Y waveguide in real time according to formula (5), the stability of the signal light path optical power can be ensured.

[0098] The typical fiber length is 3000 meters. The relative intensity noise suppression effect of FOG-3000 using double lithium niobate waveguide is as shown in Figure 6 Closed-loop control strategy:

[0099] Measure the current main light path optical power Ps and reference light path optical power Pr;

[0100] Calculate the difference ΔP = Ps-Pr;

[0101] The control system adjusts the voltage of the lithium niobate straight waveguide according to ΔP, so that ΔP→0; by setting the maximum adjustment amount ΔP of the lithium niobate Y waveguide Y Avoid the introduction of excessive noise caused by excessive adjustment depth of Y waveguide.

[0102] At the same time, measure the temperature T; according to the typical fiber ring loss and temperature relationship curve, fine-tune the bias voltage of the lithium niobate Y waveguide to pre-compensate the drift of Ps caused by the temperature change of the fiber ring, reduce the tracking pressure of the reference light path, and help to maintain the Y waveguide working in a better modulation state.

[0103]

[0104] ​It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for improving the accuracy of fiber optic gyroscopes based on lithium niobate waveguides, characterized in that, S1, the initial light generated by the light source is split into two beams, which enter the main optical path and the reference optical path respectively. The light entering the main optical path passes through the first waveguide and a sensitive fiber ring in sequence to form the main optical path signal carrying angular rate information and light source intensity noise; the light entering the reference optical path passes through the second waveguide to form the reference optical path signal carrying light source intensity noise. S2, the main optical path signal and the reference optical path signal are combined to generate a detection signal characterizing the optical power of the two signals; S3, based on the detection signal, by dynamically adjusting the first waveguide and / or the second waveguide, the optical power of the main optical path signal and / or the reference optical path signal is adjusted until the optical power of the main optical path signal and the reference optical path signal are consistent, thereby suppressing the light source intensity noise; The second waveguide is adjusted to compensate for the loss differences in the main optical path caused by different gyroscope models; The second waveguide is a lithium niobate straight waveguide, and the second waveguide is adjusted under the control of the controller; The first waveguide is adjusted to compensate for the change in optical path loss of the main optical path caused by changes in ambient temperature. The first waveguide is a lithium niobate Y waveguide, and the first waveguide is adjusted under the control of the controller; The steps for adjusting the first waveguide include: The ambient temperature of the sensitive fiber optic ring is measured to obtain temperature data; Based on the preset temperature-optical path loss model and the temperature data, the drift of the main optical path optical power is determined; Based on the drift amount, the controller generates a compensation voltage and applies it to the first waveguide to stabilize the optical power of the main optical path signal.

2. The method for improving the accuracy of fiber optic gyroscopes based on lithium niobate waveguides according to claim 1, characterized in that, Step S1 also includes, The reference optical path is also provided with a rotating reflector. After the light in the reference optical path passes through the second waveguide, it is reflected by the rotating reflector and passes through the second waveguide again.

3. The method for improving the accuracy of fiber optic gyroscopes based on lithium niobate waveguides according to claim 2, characterized in that, The rotating mirror is a 45° Faraday rotating mirror, which rotates the polarization direction of the input light by 90° to achieve fast and slow axis conversion.

4. The method for improving the accuracy of fiber optic gyroscopes based on lithium niobate waveguides according to claim 1, characterized in that, A temperature sensor is used to measure the ambient temperature of the sensitive fiber optic ring and output the temperature data to the controller. Based on the temperature data, the controller outputs a control signal to the lithium niobate Y waveguide to compensate for the change in optical path loss of the main optical path caused by temperature changes.

5. The method for improving the accuracy of fiber optic gyroscopes based on lithium niobate waveguides according to claim 1, characterized in that, Step S1 further includes, Broadband light is generated by an ASE light source, and the broadband light is split into a main optical path light and a reference optical path light using a polarization-maintaining fiber beam splitter, which are then transmitted to the main optical path and the reference optical path respectively. The polarization-maintaining fiber beam splitter includes a fiber polarizer and a 50:50 semi-transparent and semi-reflective diaphragm to improve the extinction ratio and realize optical path distribution. The 50:50 semi-transparent and semi-reflective diaphragm ensures that the incident light from the ASE light source does not directly enter the photodetector and realizes the optical path connection between the main optical path and the reference optical path.

6. The method for improving the accuracy of fiber optic gyroscopes based on lithium niobate waveguides according to claim 1, characterized in that, The main optical path signal and the reference optical path signal are received by a photodetector.

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