A fiber-optic gyroscope optical path design based on double Y waveguide to suppress relative intensity noise of light source

Abstract

The application discloses a fiber-optic gyroscope based on double Y waveguides for suppressing relative intensity noise of a light source, utilizes noise polarization correlation of interference signal light and matching reference light output by the same light source, and precisely adjusts the two Y waveguides to make the output intensity of the two Y waveguides consistent, the polarization states of the two Y waveguides orthogonal, suppresses the relative intensity noise of the gyroscope light source, and improves the gyroscope precision; the application specially designs a plurality of polarization beam splitter component light paths in the gyroscope light path, which is helpful to realize polarization state orthogonal, equal light intensity beam splitting and light combining, and further provides a specific use method of the gyroscope light path design, so that the above adjustment requirements of the same source interference signal light and the matching reference light of the fiber-optic gyroscope can be realized, the relative intensity noise of the light source is effectively reduced, and the output signal-to-noise ratio is improved. The application has the advantages of simple design structure, low implementation difficulty, fine adjustment, strong adaptability, good noise suppression effect, and the like, and is not only suitable for single-axis and multi-axis fiber-optic gyroscopes, but also suitable for fiber-optic sensors with other similar light path structures.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fiber-optic sensor technology, in particular to a fiber-optic gyroscope light path design for suppressing light source relative intensity noise based on double Y waveguides. BACKGROUND

[0002] A fiber-optic gyroscope is a new type of all-solid-state angular velocity sensor based on the Sagnac effect, and has the characteristics of good reliability, high bandwidth, short start-up time, flexible structure design, etc., and is widely used in sea, land, air and space fields. The performance of the fiber-optic gyroscope directly determines the performance of the inertial navigation system, and is the core instrument of the inertial navigation system. With the continuous development of the field of inertial navigation, the precision requirements of some new application fields for the fiber-optic gyroscope are increasing by several times or even an order of magnitude compared to before.

[0003] In view of the high-precision requirements of the new application fields for the fiber-optic gyroscope, the fiber-optic gyroscope needs to use an ASE light source with high output optical power, weak coherence and good wavelength stability. Previously, an SLD light source was used, and the optical power was small. The precision of the fiber-optic gyroscope was mainly limited by the light source shot noise. Appropriately increasing the light source power does not affect the precision of the fiber-optic gyroscope. When an ASE light source with better wavelength stability is used, the optical power is increased by more than an order of magnitude, and the light source relative intensity noise becomes the main noise source of the fiber-optic gyroscope. Under normal circumstances, the random walk noise of the gyroscope grows synchronously with the light source power, thereby limiting the improvement of the output signal-to-noise ratio and the precision of the gyroscope. Therefore, an effective light source relative intensity noise suppression method needs to be used to reduce the random walk noise, improve the output signal-to-noise ratio of the gyroscope, and then improve the output precision of the fiber-optic gyroscope.

[0004] The current optical fiber gyroscope adopted light source relative intensity noise suppression method mainly has two technical solutions of circuit noise subtraction method and orthogonal light path addition method, and the specific implementation methods have respective characteristics. The former technical solution is represented by the United States AlliedSignal company, and the main principle is to adopt two detectors to respectively receive interference signal light and idle reference light for detection, and then to perform noise subtraction processing of electrical signals. However, the effective premise is that the interference signal light and the idle reference light need to have high consistency after being converted into electrical signals, and the performance parameters of the detector and the back-end electronic device also need to have high consistency, otherwise the noise may appear negative effect of not decreasing but increasing, which is difficult to operate in practice and is not conducive to application and promotion. The technical solution of the orthogonal light path addition method is represented by the French Ixblue company, and the main principle is to realize polarization state orthogonality of the interference signal light and the idle reference light, and equal optical power, and to use polarization correlation of the homologous light to suppress the light source relative intensity noise, which is more feasible in application. A plurality of implementation schemes are proposed at home and abroad, but the common characteristic is to seriously depend on special splitting ratios or reflectivities of optical devices and other static indexes of devices. However, the actual values of these indexes are fixed, and there is often a large dispersion from the required values. In practice, it is difficult to realize accurate matching of the optical power of the signal light and the reference light through fine adjustment, which affects the suppression effect, even has the opposite effect, reduces the precision of the gyroscope, and also is difficult to guarantee the consistency of batch production of the gyroscope. SUMMARY

[0005] The technical problem solved by the present application is to overcome the shortcomings of the prior art, and to provide a kind of optical fiber gyroscope based on double Y waveguide to suppress light source relative intensity noise, which improves the technical solution of orthogonal light path addition method to suppress light source relative intensity noise, improves the signal-to-noise ratio of optical fiber gyroscope, and further improves the precision of optical fiber gyroscope. At the same time, the requirements for splitting ratio, reflectivity and other parameters of the used optical devices are greatly reduced, the operation method is simple, the consistency of debugging results is good, and it is more convenient for engineering batch application.

[0006] The technical scheme of the present application is: a kind of optical fiber gyroscope based on double Y waveguide to suppress light source relative intensity noise, comprising: light source, polarization beam splitter assembly, main Y waveguide integrated optical device, slave Y waveguide integrated optical device, optical fiber sensing ring and detector;The polarization beam splitter assembly includes first port, second port, third port and fourth port;The main Y waveguide integrated optical device includes input port and output port 1, output port 2;The slave Y waveguide integrated optical device includes input port and output port 1, output port 2;

[0007] The output end of the light source is connected to the first port of the polarization beam splitter assembly; the second port of the polarization beam splitter assembly is connected to the input port of the main Y waveguide integrated optical device; the fourth port of the polarization beam splitter assembly is connected to the input port of the slave Y waveguide integrated optical device; the third port of the polarization beam splitter assembly is connected to the detector; the output port 1 and the output port 2 of the main Y waveguide integrated optical device are both connected to the fiber sensitive ring, and the output port 1 and the output port 2 of the slave Y waveguide integrated optical device are connected through a preset axis angle.

[0008] The main Y waveguide integrated optical device and the slave Y waveguide integrated optical device can only transmit one transmission mode, wherein the main Y waveguide integrated optical device plays a role of polarization, light splitting and modulation, and the Y waveguide integrated optical device plays a role of polarization and light splitting; the light power target light splitting ratio of the output port 1 and the output port 2 of the main Y waveguide integrated optical device and the slave Y waveguide integrated optical device is 50:50, the chip polarization extinction ratio is greater than or equal to 40 dB, the polarization crosstalk of the fiber tail is less than or equal to -20 dB, and the back light reflection is less than or equal to -45 dB.

[0009] The polarization beam splitter assembly, the main Y waveguide integrated optical device, the slave Y waveguide integrated optical device and the fiber sensitive ring are connected through a polarization maintaining optical fiber; the light source and the polarization beam splitter assembly are connected through a common single-mode optical fiber or a polarization maintaining optical fiber; the detector and the polarization beam splitter assembly are connected through a polarization maintaining optical fiber or a common single-mode optical fiber.

[0010] The working waveband of the light source, the polarization beam splitter assembly, the main Y waveguide integrated optical device, the slave Y waveguide integrated optical device, the fiber sensitive ring and the detector is 850 nm or 1310 nm or 1550 nm or 1550±30 nm or 1310±30 nm or 850±30 nm waveband.

[0011] The input and output fiber tails of the polarization beam splitter assembly, the main Y waveguide integrated optical device, the slave Y waveguide integrated optical device and the fiber sensitive ring are polarization maintaining optical fibers.

[0012] The second port and the third port of the polarization beam splitter assembly output mutually orthogonal linearly polarized light; the target output light power ratio of the second port and the fourth port of the polarization beam splitter assembly is 50:50, the chip polarization extinction ratio is greater than or equal to 35 dB, the polarization crosstalk of the fiber tail is less than or equal to -25 dB, and the back light reflection is less than or equal to -45 dB.

[0013] If the fourth port of the polarization beam splitter assembly is 90° fusion spliced with the input port polarization maintaining fiber at the connection, the slave Y waveguide integrated optical device and the master Y waveguide integrated optical device adopt the same polarization axis input, that is, both are fast axis or both are slow axis.

[0014] The light source emits light of an arbitrary polarization state to the polarization beam splitter assembly through the first port of the polarization beam splitter assembly, and the light of the arbitrary polarization state is converted into linearly polarized light in the polarization beam splitter assembly; the polarization beam splitter assembly splits the received light of the arbitrary polarization state into reference light and signal light which are orthogonal to each other; the signal light is transmitted to the master Y waveguide integrated optical device through the second port of the polarization beam splitter assembly, and the signal light is polarized, split and modulated in the master Y waveguide integrated optical device; the split signal light is transmitted to the fiber sensing ring to sense the Sagnac effect, and the signal light containing the sensing information is returned to the master Y waveguide integrated optical device again to perform light interference to obtain interference signal light; the interference signal light is transmitted along the fast axis through the input port fiber of the master Y waveguide integrated optical device, and then is returned to the polarization beam splitter assembly from the fast axis along the original path of the second port fiber of the polarization beam splitter assembly; the reference light is transmitted to the slave Y waveguide integrated optical device through the fourth port fiber of the polarization beam splitter assembly, and the reference light is polarized and split in the slave Y waveguide integrated optical device; the split reference light is returned to the slave Y waveguide integrated optical device after being partially depolarized by being connected to the output port fiber at a set axis angle, is repolarized, and is matched with the interference signal light to obtain matched reference light; the matched reference light is transmitted along the fast axis of the polarization maintaining fiber through the input port fiber of the slave Y waveguide integrated optical device, and then is returned to the polarization beam splitter assembly from the slow axis after being deflected by 90° along the fourth port fiber of the polarization beam splitter assembly; the matched reference light entering the polarization beam splitter assembly along the slow axis through the fourth port is orthogonally coupled with the interference signal light entering the polarization beam splitter assembly along the fast axis through the second port to obtain synthesized light signal; and the synthesized light signal is transmitted to the detector through the third port of the polarization beam splitter assembly to be converted into an electric signal, and then is processed by a subsequent gyro circuit.

[0015] The target ratio of the optical power of the matched reference light to the interference signal light is 1:1, and the maximum deviation is allowed to be 20%.

[0016] Compared with the prior art, the present application has at least the following beneficial effects:

[0017] (1) The application utilizes the light intensity correlation between the homologous reference light and the signal light in the optical fiber gyroscope optical path, and through adding a Y waveguide optical integrated device, the output polarized light is partially depolarized and then repolarized, so that the consistency of the reference light and the interference light is better, the matching degree is higher, the light source relative intensity noise is maximized, and the output precision of the optical fiber gyroscope is further improved;

[0018] (2) The optical fiber gyroscope optical path structure of the application is simple, standard and universal devices are used, the requirements for the static parameter indexes of the optical devices are relaxed, the production cost is reduced, and batch production is facilitated;

[0019] (3) The light path design method for suppressing the light source relative intensity noise of the application can realize fine dynamic adjustment of the light source relative intensity noise suppression degree, the target result is easy to achieve, the effect is better, and it is more conducive to engineering batch application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a design scheme diagram of the existing optical fiber gyroscope light source relative intensity noise suppression based on the circuit noise subtraction method;

[0021] Figure 2 It is a design scheme diagram of the existing optical fiber gyroscope light source relative intensity noise suppression based on the orthogonal light path addition method;

[0022] Figure 3 It is a design scheme diagram of the optical fiber gyroscope light path based on the double Y waveguide for suppressing the light source relative intensity noise of the application scheme;

[0023] Figures 4-9 It is a schematic diagram of various possible schemes of the polarization beam splitter assembly using the application scheme. DETAILED DESCRIPTION

[0024] The application provides an optical fiber gyroscope based on double Y waveguide for suppressing light source relative intensity noise, which comprises a light source 1, a polarization beam splitter assembly 2, a main Y waveguide integrated optical device 3, a slave Y waveguide integrated optical device 4, an optical fiber sensitive ring 5 and a detector 6.

[0025] The light source 1 can be an ASE self-amplified radiation light source or an SLD superluminescent diode light source;

[0026] The exemplary light source 1 of the application is an ASE self-amplified radiation light source, which emits light in any polarization state;

[0027] The working waveband of the light source 1, the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the fiber sensitive ring 5 and the detector 6 can be the commonly used 850nm, 1310nm, 1550nm waveband of the fiber-optic gyroscope; further, the waveband of the ASE self-amplified radiation light source used in the optical path is 1550±30nm; the waveband of the super-radiation light SLD light source used in the optical path is 1310±30nm, 850±30nm; the waveband of the exemplary ASE self-amplified radiation light source of the application is 1550±30nm;

[0028] The output end of the main Y waveguide integrated optical device 3 comprises output end 1 and output end 2; the output end of the slave Y waveguide integrated optical device 4 comprises output end 1 and output end 2;

[0029] The light source 1, the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the fiber sensitive ring 5 and the detector 6 are connected by optical fibers;

[0030] The light source 1 is connected to the polarization beam splitter assembly 2; the polarization beam splitter assembly 2 is connected to the slave Y waveguide integrated optical device 4; the polarization beam splitter assembly 2 is connected to the fiber sensitive ring 5 through the main Y waveguide integrated optical device 3, and the polarization beam splitter assembly 2 is connected to the detector 6;

[0031] The input and output tail fibers of the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4 and the tail fiber of the fiber sensitive ring 5 can be the commonly used PANDA panda polarization maintaining optical fiber, or other bow tie, tiger, elliptical cladding, and one character type polarization maintaining optical fiber, and the cladding diameter can be commonly used specifications such as φ125μm, φ80μm, φ60μm, or special specifications such as φ50μm, φ40μm; the connecting optical fiber in the embodiment of the application adopts the PANDA panda polarization maintaining optical fiber with a cladding diameter of φ80μm;

[0032] In the embodiment of the application, the polarization maintaining optical fiber PANDA panda polarization maintaining optical fiber has a polarization axis comprising a fast axis and a slow axis, and the effective refractive indexes of the fast axis and the slow axis are different, and the speeds of light propagation are different; it can be known that the slow axis in the PANDA panda optical fiber passes through the panda eyes horizontally, and the fast axis is perpendicular to the slow axis through the center; in the embodiment of the application, the linearly polarized light initially propagates along the fast axis, and when the polarization maintaining optical fibers are connected at different port connections, the polarization axis is rotated by 90°, and the linearly polarized light will be transferred along the slow axis from the fast axis; if the linearly polarized light initially propagates along the slow axis, when the polarization maintaining optical fibers are connected at different port connections, the polarization axis is rotated by 90°, and the linearly polarized light will be transferred along the fast axis from the slow axis.

[0033] The output end of the light source 1 is connected to the first port of the polarization beam splitter assembly 2; the second port of the polarization beam splitter assembly 2 is connected to the input end of the main Y waveguide integrated optical device 3, and the output end of the main Y waveguide integrated optical device 3 is connected to the fiber sensing ring 5; the fourth port of the polarization beam splitter assembly 2 is connected to the input port of the slave Y waveguide integrated optical device 4; and the third port of the polarization beam splitter assembly 2 is connected to the input end of the detector 6, as shown in the accompanying Figure 3 .

[0034] The polarization beam splitter assembly 2 is used to convert light of any polarization state into linearly polarized signal light; the polarization beam splitter assembly 2 is used to divide the received linearly polarized signal light into mutually orthogonal signal light and reference light, and to combine the interference signal light and the matching reference light returned by each other; the main Y waveguide integrated optical device 3 polarizes, divides and modulates the signal light, and then the two beams of signal light propagate through the fiber sensing ring 5 and return to the main Y waveguide integrated optical device 3 to interfere and combine light, thereby obtaining interference signal light; the slave Y waveguide integrated optical device 4 polarizes and divides the reference light, and then the two beams of reference light are connected at a special angle through a polarization-maintaining fiber to partially depolarize, and then return to the slave Y waveguide integrated optical device 4 to be repolarized, thereby obtaining matching reference light consistent with the light intensity of the interference signal light.

[0035] The polarization beam splitter assembly 2 is used to receive interference signal light and matching reference light, and to obtain orthogonal combined light signals through orthogonal coupling; the detector 6 is used to receive the orthogonal combined light signals output by the polarization beam splitter assembly 2; and the detector 6 is a photodetector.

[0036] The target power ratio of the matching reference light to the interference signal light is 1:1;

[0037] The main Y waveguide integrated optical device 3 polarizes, modulates and equally divides the signal light, thereby obtaining two beams of interference signal light entering the fiber sensing ring 5, and finally returning to the main Y waveguide integrated optical device 3 to combine and interfere, and then transmitting the interference signal light to the polarization beam splitter assembly 2. The two beams of interference signal light are modulated by peripheral circuit signals, and the modulation depth of the circuit signals can be used to modulate the interference of the two beams of interference light in the main Y waveguide integrated optical device 4, so as to adjust the light intensity, and the modulation depth can be selected between [π / 2, π).

[0038] The target output light power ratio of the second port to the fourth port of the polarization beam splitter assembly 2 is 50:50; and the target output light power ratio of the first port to the third port is 50:50;

[0039] The output extinction ratio of the first port to the second port and the first port to the fourth port of the polarization beam splitter assembly 2 is not less than 20dB;

[0040] The orthogonal output lines of the second port and the fourth port of the polarization beam splitter assembly 2 respectively propagate in the fast axis and the slow axis of the respective pigtail fiber. Figure 3 ;

[0041] The polarization beam splitter assembly 2 used in the technical solution of the present application is shown in the structure of Figure 4 The polarization beam splitter assembly 2 can have other structures as shown in Figure 5 , attached Figure 6 , attached Figure 7 , attached Figure 8 , attached Figure 9 ;

[0042] In the polarization beam splitter assembly 2 used in the technical solution of the present application, the second port of the polarization beam splitter assembly 2 is connected to the input port of the main Y waveguide integrated optical device 3 to receive the modulated interference signal light returned from the fiber sensitive ring 5, and the fourth port is connected to the input port of the slave Y waveguide integrated optical device 4 to receive the matching reference light returned through the output pigtail fiber off-axis connection and re-polarization, and the interference signal light and the matching reference light are orthogonally coupled in the polarization beam splitter assembly 2, and the intensity is superimposed to achieve consistent intensity to the detector 6, satisfying the condition of coherent intensity noise orthogonal addition method of light source cancellation suppression.

[0043] The main Y waveguide integrated optical device 3 and the slave Y waveguide integrated optical device 4 are proton exchange optical Y waveguide integrated optical devices, both of which are single polarization waveguides (only TE mode can be transmitted) with linearly polarized light output, and the chip extinction ratio is greater than 45dB, and the output end includes output end 1 and output end 2, and the optical power splitting ratio target value of both is 50:50;

[0044] In the technical solution of the present application, the optical power splitting ratio target value of the two output ends of the main Y waveguide integrated optical device 3 is 50:50, and the two beams of signal light output are propagated in clockwise and counterclockwise directions respectively after passing through the fiber sensitive ring 5, and then return to the main Y waveguide integrated optical device 3 inside to be combined and interfered, and the interference signal light formed is returned to the polarization beam splitter assembly 2.

[0045] In the technical solution of the present application, the optical power splitting ratio target value of the two output ends of the slave Y waveguide integrated optical device 4 is 50:50, and the two beams of light signal output are returned to the slave Y waveguide integrated optical device inside after off-axis butt joint, and then combined, and the matching reference light formed after re-polarization filtering is returned to the polarization beam splitter assembly 2.

[0046] In the embodiment of the present application, the pigtail fiber of the ASE self-amplified radiation light source is a single-mode fiber, and the pigtail fibers of the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the fiber sensitive ring 5 and the detector 6 are all polarization maintaining fibers.

[0047] In the embodiment of the present application, the input ends of the main Y-waveguide integrated optical device 3 and the slave Y-waveguide integrated optical device 4 are both fast-axis input, that is, the fast axis of the polarization maintaining optical fiber is consistent with the TE mode of the integrated Y-waveguide. At this time, the input end of the main Y-waveguide integrated optical device 3 is connected to the input end of the polarization maintaining fiber of the second port (fast-axis output) of the polarization splitting component 2 at a 0° target alignment angle, and the input end of the slave Y-waveguide integrated optical device 4 is connected to the input end of the polarization maintaining fiber of the fourth port (slow-axis output) of the polarization splitting component 2 at a 90° target alignment angle.

[0048] If the input ends of the two Y-waveguide integrated optical devices are both slow-axis input, the input end of the polarization splitting component 2 needs to be adjusted to a fast-axis output, and the input end of the Y-waveguide integrated optical device needs to be adjusted to a 90° target alignment angle.

[0049] In other embodiments, if the input end of the main Y-waveguide integrated optical device 3 is fast-axis input (that is, the fast axis of the polarization maintaining optical fiber is consistent with the TE mode of the integrated Y-waveguide, and fast-axis light can propagate), and the input end of the slave Y-waveguide integrated optical device 5 is slow-axis input (that is, the slow axis of the polarization maintaining optical fiber is consistent with the TE mode of the integrated Y-waveguide, and slow-axis light can propagate). At this time, the input end of the main Y-waveguide integrated optical device 3 is connected to the input end of the polarization maintaining fiber of the second port (fast-axis output) of the polarization splitting component 2 at a 0° target alignment angle, and the input end of the slave Y-waveguide integrated optical device 4 is connected to the input end of the polarization maintaining fiber of the fourth port (slow-axis output) of the polarization splitting component 2 at a 0° target alignment angle.

[0050] In other cases, if the input end of the main Y-waveguide integrated optical device 3 is slow-axis input, and the input end of the slave Y-waveguide integrated optical device 4 is fast-axis input, the polarization maintaining fiber alignment angles are both 0° alignment angle, but the second port and the fourth port need to be interchanged.

[0051] In the embodiment of the application, the input end of the master Y-waveguide integrated optical device 3 and the input end of the slave Y-waveguide integrated optical device 4 are both fast-axis input, and the output is fast-axis output; wherein, when the polarization maintaining optical fiber is connected, the tail fiber at the connection between the second port (fast-axis output) of the polarization beam splitter assembly 2 and the input port of the master Y-waveguide integrated optical device 3 is connected at 0°, and the tail fiber at the connection between the output port of the master Y-waveguide integrated optical device 3 and the optical fiber sensitive ring 5 is connected at 0°, so as to ensure that the interference optical signal is transmitted along the fast axis; the tail fiber at the connection between the fourth port (slow-axis output) of the polarization beam splitter assembly 2 and the input port of the slave Y-waveguide integrated optical device 4 is connected at 90°, so that the reference light is transmitted along the tail fiber from the slow axis to the fast axis; the tail fiber at the output port 1 and the output port 2 of the slave Y-waveguide integrated optical device 4 is connected at a special alignment angle, and the target alignment angle is from 50° to 90°, and the actual ratio of the reference value in the table will be slightly deviated, the alignment angle is related to the modulation depth parameter, the Y-waveguide insertion loss and other indicators, and needs to be accurately determined by experiment.

[0052] In actual production, after the optical path is connected, the modulation depth parameter can be fixed first, the fourth port of the polarization beam splitter assembly 2 is disconnected, the tail fiber is well treated, and the output power of the third port of the polarization beam splitter assembly 2 is measured; the second port of the polarization beam splitter assembly 2 is disconnected, the tail fiber is well treated, the tail fiber between the input port of the slave Y-waveguide integrated optical device 4 and the fourth port of the polarization beam splitter assembly 2 is connected again at different alignment angles, the output power of the third port of the polarization beam splitter assembly 2 is measured, until the powers of the two are approximately equal, and the misalignment angle θ is recorded. Thus, the accurate correspondence table of the modulation depth and the alignment angle is established, so as to guide the subsequent optical path tail fiber misalignment connection, and the initial reference value of the alignment angle is shown in Table 1.

[0053] Table 1: Correspondence table of several typical modulation depth parameters and alignment angle θ reference values

[0054] Serial number Modulation depth parameter φ Off-axis angle θ reference value Remarks 1 π / 2 55° For reference, actual up and down slightly floating 2 2 / 3π 63° For reference, actual up and down slightly floating 3 3 / 4π 69° For reference, actual up and down slightly floating 4 4 / 5π 73° For reference, actual up and down slightly floating 5 5 / 6π 74.5° For reference, actual up and down slightly floating 6 7 / 8π 79° For reference, actual up and down slightly floating 7 8 / 9π 80° For reference, actual up and down slightly floating 8 9 / 10π 81° For reference, actual up and down slightly floating 9 10 / 11π 82° For reference, actual up and down slightly floating 10 11 / 12π 82.5° For reference, actual up and down slightly floating 11 12 / 13π 83° For reference, actual up and down slightly floating 12 13 / 14π 83.5° For reference, actual up and down slightly floating 13 14 / 15π 84° For reference, actual up and down slightly floating 14 15 / 16π 84.5° For reference, actual up and down slightly floating 15 16 / 17π 84.7° For reference, actual up and down slightly floating 16 17 / 18π 85° For reference, actual up and down slightly floating

[0055] Note: other modulation depths can refer to the corresponding reference initial alignment angles in the corresponding intervals on both sides of the table, and the maximum is not more than 90°.

[0056] In the technical scheme of the present application, the polarization beam splitter assembly 2 divides the light signal output by the light source 1 into two beams, one of which is signal light transmitted along the second port output fiber (polarization maintaining fiber fast axis), and the other of which is reference light transmitted along the fourth port output fiber (polarization maintaining fiber slow axis). The signal light is transmitted to the main Y waveguide integrated optical device 3 through the second port of the polarization beam splitter assembly 2, and is divided into signal light 1 and signal light 2 through the output end 1 and the output end 2 of the main Y waveguide integrated optical device 3, and the signal light 1 and the signal light 2 enter the fiber sensing ring 5 and propagate in the fiber sensing ring 5 in opposite directions, respectively. The reference light is transmitted to the slave Y waveguide integrated optical device 4 through the fourth port of the polarization beam splitter assembly 2, and is divided into reference light 1 and reference light 2 through the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4, and the reference light 1 and the reference light 2 are transmitted through the polarization maintaining fiber tail fiber, and are connected through a specific axis angle, and the modulation depth of the axis angle is determined by the peripheral circuit signal applied to the main Y waveguide integrated optical device 3, and a larger modulation depth corresponds to a larger axis angle close to 90°, as shown in Table 1, so as to ensure that the interference signal light output after the signal light 1 and the signal light 2 interfere, and the matching reference light synthesized after the reference light 1 and the reference light 2 are polarized and output are as equal as possible. The interference signal light and the matching reference light are orthogonally coupled and combined in the polarization beam splitter assembly 2; the orthogonally combined light signal after the combination is returned to the detector 6 through the third port of the polarization beam splitter assembly 2, and the light signal is converted into an electric signal. Thus, the suppression of the light source relative intensity noise is realized without changing the circuit and algorithm, the optical path loss is reduced, the signal-to-noise ratio of the fiber optic gyroscope is improved, and the precision of the fiber optic gyroscope is improved.

[0057] In the technical scheme of the present application, the polarization directions of the interference signal light and the matching reference light are perpendicular and do not interfere, and only intensity superposition occurs when reaching the detector, so that the influence of the parasitic coherent effect on the gyroscope precision can be suppressed.

[0058] The optical fiber gyroscope optical path design based on the double Y waveguide to suppress the light source relative intensity noise is proposed in the present application, and the orthogonal addition compensation effect of the light source relative intensity noise can affect and characterize the output precision of the gyroscope. By achieving good light source relative intensity noise suppression, high output precision of the fiber optic gyroscope can be realized.

[0059] The optical path provided by the application designs a polarization beam splitter component 2, which has two input ports and two output ports; wherein the first port is an input port, the second port and the fourth port are forward output ports, and the third port is a reverse output port; wherein the first port receives light of any polarization state emitted by a light source 1, the second port emits and receives (through a main Y waveguide integrated optical device 3) signal light, the fourth port emits and receives (through a slave waveguide phase modulator 4) reference light, and the signal light and the reference light emitted and received by the first port and the fourth port are mutually orthogonal linearly polarized light; the returned interference signal light and the matching reference light are orthogonally coupled in the polarization beam splitter component 2; and the third port receives the orthogonally combined light signal output (a detector 6) after the polarization beam splitter component 2 is coupled.

[0060] The optical path provided by the application also designs the polarization beam splitter component 2, which has two input ports and two output ports; wherein the tail fibers connected to the second port and the fourth port must be polarization maintaining optical fibers, and the tail fibers connected to the remaining ports can be polarization maintaining optical fibers or single mode optical fibers, depending on the internal structure of the polarization beam splitter component. The component can be a combination of two separate functional devices or a combination integrated into one functional device, and generally has six typical structures. See the following drawings for details. Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 .

[0061] In structure 1, the polarization beam splitter component is composed of a polarizer and a 2*2 polarization maintaining beam splitter; the input port of the polarizer serves as the first port of the polarization beam splitter component, receives light of any polarization state output by a light source and converts it into linearly polarized light; the output port of the polarizer is connected to port 1 (input end) of the polarization maintaining beam splitter, and the linearly polarized light is input into the polarization maintaining beam splitter; ports 2 and 4 of the polarization maintaining beam splitter serve as the forward output ports of the polarization beam splitter component, i.e., the second port and the fourth port, and divide the linearly polarized light into linearly polarized light with a splitting ratio target value of 50:50 and mutual orthogonality, which is output from ports 2 and 4 of the polarization maintaining beam splitter, respectively; the mutually orthogonal linearly polarized light returned from ports 2 and 4 of the polarization maintaining beam splitter is input into the polarization maintaining beam splitter, and after orthogonal coupling, the light is output in a bundled manner from port 3 of the polarization maintaining beam splitter, which serves as the third port of the polarization beam splitter component; in this structure, the tail fibers of the polarizer and the 2*2 polarization maintaining beam splitter are polarization maintaining optical fibers, the tail fiber connected to the detector is preferably a polarization maintaining optical fiber, and the tail fiber connected to the light source can be a single mode optical fiber.

[0062] ​​​​​The structure 2, the polarization beam splitter assembly is composed of a 3-port polarization maintaining optical circulator and a 1*2 fiber polarization beam splitter / combiner. The port 1 (input end) of the polarization maintaining optical circulator, as the first port of the polarization beam splitter assembly, receives the light of arbitrary polarization state output by the light source. The port 2 (forward input, reverse output end) of the polarization maintaining optical circulator is connected to the port III (splitting input end, combining output end) of the 1*2 fiber polarization beam splitter / combiner. The forward output light of the polarization maintaining optical circulator is polarized into linearly polarized light and input into the fiber polarization beam splitter / combiner. At the same time, the input light is split into linearly polarized light with a target splitting ratio of 50:50 and orthogonal to each other, which is output from the port I and the port II of the fiber polarization beam splitter / combiner, respectively. The port I and the port II of the fiber polarization beam splitter / combiner, as the forward output ports of the polarization beam splitter assembly, are the second port and the fourth port, respectively. The linearly polarized light returned from the port I and the port II of the fiber polarization beam splitter / combiner is input into the fiber polarization beam splitter / combiner for orthogonal coupling, and then is output from the port III of the fiber polarization beam splitter / combiner. The port III of the fiber polarization beam splitter / combiner is connected to the port 2 (forward input, reverse output end) of the polarization maintaining optical circulator. Finally, it is output from the port 3 (output end) of the polarization maintaining optical circulator, which is the third port of the polarization beam splitter assembly. In this structure, the pigtail of the 1*2 fiber polarization beam splitter / combiner and the polarization maintaining optical circulator is a polarization maintaining optical fiber. The tail fiber connected to the detector is preferably a polarization maintaining optical fiber, and can also be a single-mode optical fiber. The tail fiber connected to the light source is a single-mode optical fiber.

[0063] The structure 3, the polarization beam splitter assembly is composed of a 3-port fiber sensitive circulator and a 1*2 fiber polarization beam splitter / combiner, the port 1 (input end) of the fiber sensitive circulator is used as the first port of the polarization beam splitter assembly, and receives the light of an arbitrary polarization state output by the light source; the port 2 (forward input, reverse output end) of the fiber sensitive circulator is connected to the port III (splitting input end, combining output end) of the 1*2 fiber polarization beam splitter / combiner, and the forward output light of the fiber sensitive circulator is input into the fiber polarization beam splitter / combiner, and the input light is split into target split ratios of 50:50 and mutually orthogonal linearly polarized lights which are respectively output from the ports I and II of the fiber polarization beam splitter / combiner; the ports I and II of the fiber polarization beam splitter / combiner are used as the forward output ports (the second port and the fourth port) of the polarization beam splitter assembly, and the mutually orthogonal linearly polarized lights returned from the ports I and II of the fiber polarization beam splitter / combiner are input into the fiber polarization beam splitter / combiner for orthogonal coupling, and then combined and output from the port III of the fiber polarization beam splitter / combiner; the port III of the fiber polarization beam splitter / combiner is connected to the port 2 (forward input, reverse output end) of the fiber circulator, and finally output from the port 3 (output end) of the fiber circulator; the port 3 of the fiber circulator is used as the third port of the polarization beam splitter assembly; in this structure, the tail fibers of the ports I and II of the 1*2 fiber polarization beam splitter / combiner are all polarization maintaining fibers, the tail fiber of the port III can be a common fiber or a polarization maintaining fiber, and the tail fiber of the fiber circulator is a single-mode fiber; the tail fibers of the connected detectors and light sources are single-mode fibers.

[0064] The polarization beam splitter assembly is composed of a 4-port fiber splitter and a 1*2 fiber polarization beam splitter / combiner, the port 1 (input end) of the fiber splitter is used as the first port of the polarization beam splitter assembly, and receives the light of any polarization state output by the light source, the port 2 (forward input, reverse output end) of the fiber splitter is connected to the port III (beam splitting input end, beam combining output end) of the 1*2 fiber polarization beam splitter / combiner, and the forward output light of the fiber splitter is input into the fiber polarization beam splitter / combiner, and the input light is split into two linearly polarized lights with a target splitting ratio of 50:50 and mutually orthogonal, which are output from the port I and the port II of the fiber polarization beam splitter / combiner, respectively; the port I and the port II of the fiber polarization beam splitter / combiner are used as the forward output ports (the second port and the fourth port) of the polarization beam splitter assembly, and the mutually orthogonal linearly polarized lights returned from the port I and the port II of the fiber polarization beam splitter / combiner are input into the fiber polarization beam splitter / combiner for orthogonal coupling, and then the coupled lights are combined and output from the port III of the fiber polarization beam splitter / combiner, the port III of the fiber polarization beam splitter / combiner is connected to the port 2 (forward input, reverse output end) of the fiber splitter, and finally output from the port 3 (output end) of the fiber splitter, the port 3 of the fiber splitter is used as the third port of the polarization beam splitter assembly, and the port 4 of the fiber splitter is used as a vacant port and processed by means of increasing echo loss, such as inclined throwing or small circle disc; in this structure, the tail fibers of the port I and the port II of the 1*2 fiber polarization beam splitter / combiner are all polarization maintaining fibers, the tail fiber of the port III and the tail fiber of the fiber splitter can be a single-mode fiber, and the tail fibers of the connected light source and detector are single-mode fibers.

[0065] The application also provides a use method of the optical fiber gyroscope optical path design based on the double Y waveguide for suppressing the relative intensity noise of the light source, comprising:

[0066] The light source 1 emits light of any polarization state, which is transmitted to the polarization beam splitter assembly 2 through the first port of the polarization beam splitter assembly 2, and is converted into two linearly polarized lights which are mutually orthogonal; the two linearly polarized lights are output from the polarization beam splitter assembly 2 through the second port and the fourth port of the polarization beam splitter assembly, respectively; that is, the polarization beam splitter assembly 2 divides the received linearly polarized signal light into signal light and reference light which are mutually orthogonal;

[0067] The signal light is transmitted to the main Y waveguide integrated optical device 3 through the second port of the polarization beam splitter assembly 2, and is subjected to polarization, modulation and splitting, and then the split signal light is transmitted to the fiber sensing ring 5 to propagate clockwise and counterclockwise to generate Sagnac effect, and then the two signal lights are returned to the main Y waveguide integrated optical device 3 through the fiber sensing ring 5 to interfere and combine light, and an interference signal light is obtained, which is transmitted to the polarization beam splitter assembly 2 through the second port of the polarization beam splitter assembly 2;

[0068] The reference light is transmitted through the fourth port of the polarization beamsplitter assembly 2 to the Y-waveguide integrated optical device 4 for reference light polarization and beam splitting. The split reference light is partially depolarized by connecting two pigtails at a specific off-axis angle at the output end. The partially depolarized reference light returns to the Y-waveguide integrated optical device 4 for beam combining and repolarization to obtain a matched reference light. The matched reference light is transmitted through the fourth port of the polarization beamsplitter assembly 2 to the polarization beamsplitter assembly 2.

[0069] The interference signal light is input in reverse from the second port of the polarization beamsplitter assembly 2, and the reference light is input in reverse from the fourth port of the polarization beamsplitter assembly 2. Ideally, the two are orthogonally polarized lights. They are orthogonally coupled inside the polarization beamsplitter assembly 2 to synthesize an optical signal. After the interference signal light and the matching reference light are coupled inside the polarization beamsplitter assembly 2, they form an orthogonally synthesized optical signal, which is transmitted to the detector 6 through the third port of the polarization beamsplitter assembly 2.

[0070] The specific steps for orthogonal coupling and synthesizing optical signals include:

[0071] ① The output port of the light source 1 is connected to the first port of the polarization beam splitter assembly 2, and will output light of arbitrary polarization state, splitting it into linearly polarized signal light and reference light that are orthogonal to each other;

[0072] ② Connect the second port of the polarization beam splitter assembly 2 to the input port of the main Y-waveguide integrated optical device 3, transmit the signal light to the main Y-waveguide integrated optical device 3 for polarization and modulation, and split the signal light into signal light 1 and signal light 2 through the output terminals 1 and 2 of the main Y-waveguide integrated optical device 3;

[0073] ③ The output terminals 1 and 2 of the main Y-waveguide integrated optical device 3 are connected to the two input terminals of the fiber sensing ring 5. Signal light 1 and signal light 2 propagate in clockwise and counterclockwise directions respectively in the fiber sensing ring 5. Sensing the Sagnac effect, signal light 1 and signal light 2 propagating in clockwise and counterclockwise directions return to the main Y-waveguide integrated optical device 3 after passing through the fiber sensing ring 5. Optical interference is performed in the main Y-waveguide integrated optical device 3 to obtain the modulated interference signal light I1.

[0074] ④ After the polarization-maintaining pigtail at the fourth port of polarization beam splitter assembly 2 is subjected to end-face oblique polishing or small looping for high return loss treatment, the optical power intensity of the interference signal light obtained by testing through the pigtail at the third port of polarization beam splitter assembly 2 is denoted as I1.

[0075] ⑤connecting the fourth port of the polarization beam splitter assembly 2 with the input port of the slave Y waveguide integrated optical device 4, transmitting the reference light to the slave Y waveguide integrated optical device 4 for polarization, and dividing the reference light into reference light 1 and reference light 2 through the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4; connecting the polarization maintaining fiber pigtails of the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4 through a specific axis angle biasing and axis connecting, transmitting and partially depolarizing the reference light 1 and the reference light 2 through the polarization maintaining fiber pigtails of the output port respectively, and then returning to the slave Y waveguide integrated optical device 4 again, re-polarizing through the slave Y waveguide integrated optical device 4 to obtain matching reference light I2;

[0076] ⑥interference signal light and matching reference light are orthogonally coupled and combined in the polarization beam splitter assembly 2, and the total optical power intensity I0 of the orthogonally combined optical signal of the interference signal light and the matching reference light obtained through the polarization beam splitter assembly 2 third port pigtail test is recorded as I0, and the axis angle of the polarization maintaining fiber of the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4 is adjusted to be connected through biasing, so that I1≈I2, because I2=I0-I1, actually only I0 needs to be tested, and I0≈2I1 can be met.

[0077]

[0082] ⑧after either of the above two steps is achieved, the polarization beam splitter assembly 2 third port pigtail is connected with the detector 6 pigtail, so that the orthogonally combined optical signal is returned to the detector 6 through the polarization beam splitter assembly 2 third port, and the optical signal is converted into an electrical signal.

[0079] The biasing angle in the application is determined according to the initial modulation depth of the master Y waveguide integrated optical device, in the example of the application, a large modulation depth corresponds to a biasing angle closer to 90° (a higher depolarization degree), so as to ensure that the interference signal light output after the interference of the signal light 1 and the signal light 2 is equal to the matching reference light output after the re-polarization of the combined reference light 1 and reference light 2 as much as possible.

[0080] The application simultaneously uses the modulation depth of the master Y waveguide integrated optical device 3 and the output pigtail biasing angle of the slave Y waveguide integrated optical device 4 to perform accurate control, which can ensure that the interference signal light and the matching reference light are orthogonal and the optical power is equal,

[0081] ​The signal light and the reference light split by the polarization beam splitter assembly will have differences in the transmission process, cannot be completely consistent and orthogonal, and the output light intensity error will cause the noise of the interference type digital closed loop fiber optic gyroscope formed by the subsequent main Y waveguide integrated optical device and the fiber sensitive ring to change, further affecting the precision of the fiber optic gyroscope, the modulation depth of the main Y waveguide integrated optical device in the fiber optic gyroscope digital closed loop system is adjusted to further compensate the light intensity difference between the interference signal light and the matching reference light, thereby reducing the light source relative intensity noise, so that the fiber optic gyroscope has a high output signal-to-noise ratio, thereby improving the output precision of the gyroscope; the output light intensity values of the measured interference signal light, the orthogonal synthesized light and the matching reference light are measured, and the modulation depth and the off-axis angle are calculated, the modulation depth is used to change the modulated interference signal light, and the off-axis angle is used to change the matching reference light, so that the matching reference light and the modulated interference signal light realize accurate equal light intensity matching.

[0082] The technical scheme of the present application designs a polarization beam splitter assembly, cooperates with two Y waveguides, uses the reference light of the idle fourth port of the polarization beam splitter, and realizes light intensity matching through off-axis butt joint and re-polarization of the Y waveguide, so that the polarization degree of the polarization light of the reference light route changes, and the power of the output matching reference light is consistent with the modulated interference signal light returned by the main Y waveguide light path, and the requirements for optical devices are greatly reduced, which is beneficial to orthogonal light cancellation and suppression.

[0083] The technical scheme of the present application uses the orthogonal light path addition method, uses the light intensity correlation between the reference light and the signal light emitted by the same light source to cancel the noise, realizes the light source relative intensity noise suppression at the eigenfrequency of the fiber optic gyroscope, has good compatibility with the full digital closed loop processing technology commonly used in high-precision fiber optic gyroscopes, has strong implementability, does not need to increase or change the hardware design of the modulation and demodulation circuit, greatly reduces the requirements for optical devices, and has relatively simple debugging process and low implementation difficulty.

[0084] One specific embodiment of the present application is disclosed as Figure 3 , a fiber optic gyroscope optical path design for suppressing light source relative intensity noise based on double Y waveguides, in order to illustrate the effectiveness of the method, the above technical scheme of the present application is described in detail through specific embodiments, and the specific implementation steps are as follows:

[0085] The present application provides a fiber optic gyroscope optical path design for suppressing light source relative intensity noise based on double Y waveguides, comprising: a light source 1, a polarization beam splitter assembly 2, a main Y waveguide integrated optical device 3, a slave Y waveguide integrated optical device 4, a fiber sensitive ring 5 and a detector 6.

[0086] The light source 1, the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the fiber sensitive ring 5 and the detector 6 are connected by optical fibers;

[0087] The light source 1 is an ASE self-amplified radiation light source;

[0088] The light source 1 is connected with the polarization beam splitter assembly 2 by a single-mode optical fiber, the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4 and the fiber sensitive ring 5 are connected by polarization maintaining optical fibers; the detector 6 can be connected with the polarization beam splitter assembly 2 by a polarization maintaining optical fiber or a single-mode optical fiber; the output ports of the slave Y waveguide integrated optical device 4 can be connected by an additional polarization maintaining optical fiber or directly connected by a pigtail fiber;

[0089] The polarization beam splitter assembly 2 is connected with the light source 1, the detector 6, the main Y waveguide integrated optical device 3 and the slave Y waveguide integrated optical device 4 respectively, the polarization beam splitter assembly 2 is connected with the fiber sensitive ring 5 through the main Y waveguide integrated optical device 3, and the polarization beam splitter assembly 3 is connected with the detector 6;

[0090] In one embodiment of the present application, the first port of the polarization beam splitter assembly 2 is connected with the ASE self-amplified radiation light source 1; the ASE self-amplified radiation light source emits light in an arbitrary polarization state;

[0091] The second port of the polarization beam splitter assembly 2 is connected with the input end of the main Y waveguide integrated optical device 3, the output end 1 and the input end 2 of the main Y waveguide integrated optical device 3 are connected with the fiber sensitive ring 5, the fourth port of the polarization beam splitter assembly 2 is connected with the input end of the slave Y waveguide integrated optical device 4, and the third port of the polarization beam splitter assembly 2 is connected with the detector 6, such as Figure 1 ;

[0092] The output ports of the slave Y waveguide integrated optical device 4 are directly connected by polarization maintaining optical fiber pigtails;

[0093] The polarization beam splitter assembly 2 is used for converting received light in an arbitrary polarization state into linearly polarized light; the polarization beam splitter assembly 2 is used for dividing output light signals into two mutually orthogonal reference light and signal light and bidirectional transmission; the main Y waveguide integrated optical device 3 performs polarization, modulation and beam splitting on the signal light, the split signal light returns to the main Y waveguide integrated optical device 3 again after passing through the fiber sensitive ring 5 to interfere and combine light, and a modulated interference light signal is obtained;

[0094] The slave Y waveguide integrated optical device 4 performs polarization and splitting on the reference light, the split reference light is partially depolarized after being butt-jointed by the polarization maintaining optical fiber tail, and then returns to the slave Y waveguide integrated optical device 4 again to be repolarized, and a matching reference light is obtained;

[0095] The polarization beam splitter assembly 2 is used for receiving the returned modulated interference light and the matching reference light, both of which are mutually orthogonal linearly polarized light, and after coupling and combining, the orthogonal combined light signal is obtained; the detector 5 is used for receiving the orthogonal combined light signal output by the polarization beam splitter assembly 2.

[0096] The target optical power ratio of the modulated interference light and the matching reference light is 1:1.

[0097] The main Y waveguide integrated optical device 3 splits and modulates the signal light by 50:50, and then two linearly polarized signal lights are obtained and enter the optical fiber sensitive ring 5, and then return to the modulator 3 for beam combining interference to obtain interference signal light, and then the interference signal light is transmitted to the polarization beam splitter assembly 2, and the peripheral gyro circuit signal is modulated, and the main Y waveguide integrated optical device 3 is modulated by the circuit through the modulation depth parameter to adjust the light intensity of the interference signal light.

[0098] The target output optical power ratio of the second port and the fourth port of the polarization beam splitter assembly 3 is 50:50; further, the first port of the polarization beam splitter assembly 2 is a forward input port, the second port and the fourth port are forward output and reverse input ports, and the third port is a reverse output port.

[0099] The polarization beam splitter assembly used in the technical scheme of the application, wherein the first port of the polarization beam splitter assembly 2 receives the arbitrary polarization state light output from the light source 1, the second port and the fourth port output signal light and reference light with equivalent intensity in the forward direction, and after transmission and application of other optical path devices, the interference signal light and the matching reference light with equivalent intensity are returned in the reverse direction.

[0100] The polarization state of the modulated interference signal light and the matching reference light is orthogonal, and the light intensity remains consistent, which meets the condition of relative intensity noise cancellation subtraction of the same light source, and after orthogonal coupling in the polarization beam splitter assembly 2, the intensity is superimposed and output in the reverse direction through the third port to reach the detector 6.

[0101] The working waveband of the self-amplified radiation (ASE) light source is 1550±30nm.

[0102] The output end of the main Y waveguide integrated optical device 3 includes output end 1 and output end 2, and the output end of the Y waveguide integrated optical device 4 includes output end 1 and output end 2.

[0103] The detector 6 is a photodetector, and the pigtail is preferably a polarization maintaining optical fiber, and can also be a single-mode optical fiber.

[0104] The main Y waveguide integrated optical device 3 and the slave Y waveguide integrated optical device 4 are both proton exchange integrated optical Y waveguide integrated optical devices, and are both single polarization waveguides (only TE mode can be transmitted) with linearly polarized light as target output light, and the extinction ratio is greater than 45dB; the target light power splitting ratio of the output end 1 and the output end 2 of the main Y waveguide integrated optical device 3 is 50:50, and the target light power splitting ratio of the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4 is 50:50;

[0105] In the embodiment, the input ends of the main Y waveguide integrated optical device 3 and the slave Y waveguide integrated optical device 4 can be fast axis input, that is, the fast axis of the polarization maintaining optical fiber is consistent with the TE mode of the integrated Y waveguide, at this time, the input end of the polarization maintaining tail fiber of the main Y waveguide integrated optical device 3 corresponds to the input end of the polarization maintaining tail fiber of the second port (fast axis output) of the polarization beam splitting component 2 with a 0° polarization axis angle connection, and the input end of the polarization maintaining tail fiber of the slave Y waveguide integrated optical device 4 corresponds to the input end of the polarization maintaining tail fiber of the fourth port (slow axis output) of the polarization beam splitting component 2 with a 90° polarization axis angle connection.

[0106] In the technical scheme of the application, the light power splitting ratio of the two output ends of the two proton exchange integrated optical Y waveguide integrated optical devices is 50:50, the same light source is output, the clockwise and counterclockwise two signal lights modulated by the main Y waveguide integrated optical device 3 are returned to the inside of the modulator 3 of the main Y waveguide integrated optical device after passing through the optical fiber sensitive ring 5, are combined, interfere, and form the modulated interference signal light transmission back to the polarization beam splitter component 2.

[0107] In an embodiment of the application, the tail fiber of the ASE self-amplified radiation light source is a common single-mode optical fiber.

[0108] The tail fibers of the polarization beam splitter component 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the optical fiber sensitive ring 5 and the detector 6 all adopt polarization maintaining optical fibers.

[0109] The polarization maintaining optical fiber is a panda PANDA type polarization maintaining optical fiber, including a fast axis and a slow axis; the effective refractive indexes of the fast axis and the slow axis of the polarization maintaining optical fiber are different, and the speeds of light propagation are different.

[0110] In the panda type optical fiber, the slow axis passes through the center of the panda eye horizontally, and the fast axis is perpendicular to the center; in general, linearly polarized light propagates along the fast axis, and when the two ports are connected, the light will propagate along the slow axis after being rotated by 90°.

[0111] The main Y waveguide integrated optical device 3 and the slave Y waveguide integrated optical device 4 are both proton exchange integrated optical Y waveguide integrated optical devices, and are both single polarization waveguides (only TE mode can be transmitted) with linearly polarized light as target output light, and the extinction ratio is greater than 45dB, and both are fast axis input.

[0112] The signal light connected with the input end of the main Y waveguide integrated optical device 3 is output along the fast axis from the second port of the polarization beam splitter assembly 2, and the reference light connected with the input end of the slave Y waveguide integrated optical device 4 is output along the slow axis from the fourth port of the polarization beam splitter assembly 2.

[0113] The fourth port of the polarization beam splitter assembly 2 is connected with the pigtail of the slave Y waveguide integrated optical device 4 at an angle of 90° when the polarization maintaining optical fiber is connected, so that the matching reference light is changed from the slow axis to the fast axis.

[0114] The remaining connection points are all connected at an angle of 0°, so as to ensure that the interference signal light is transmitted along the fast axis.

[0115] In the technical scheme of the present application, the polarization beam splitter assembly 2 divides the light signal output by the light source 1 into two beams, one of which is signal light transmitted along the output pigtail of the second port (the fast axis of the polarization maintaining optical fiber), and the other of which is reference light transmitted along the output pigtail of the fourth port (the slow axis of the polarization maintaining optical fiber). The signal light is transmitted to the main Y waveguide integrated optical device 3 through the second port of the polarization beam splitter assembly 2, and is divided into signal light 1 and signal light 2 through the output end 1 and the output end 2 of the main Y waveguide integrated optical device 3, and the signal light 1 and the signal light 2 are respectively transmitted in the optical fiber sensitive ring 5 according to the counterclockwise and clockwise propagation sensitive Sagnac effect. The reference light is transmitted to the slave Y waveguide integrated optical device 4 through the fourth port of the polarization beam splitter assembly 2, and is divided into reference light 1 and reference light 2 through the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4, and the reference light 1 and the reference light 2 are respectively transmitted through the polarization maintaining optical fiber pigtail, and are connected at a specific axis angle. The modulation depth parameter of the signal applied to the main Y waveguide integrated optical device 3 by the peripheral circuit determines the axis angle, and the modulation depth parameter close to π corresponds to the axis angle close to 90°, so as to ensure that the interference signal light output after the interference of the signal light 1 and the signal light 2 is equal to the matching reference light synthesized after the reference light 1 and the reference light 2 are output. The interference signal light and the matching reference light are orthogonally coupled and combined in the polarization beam splitter assembly 2. The orthogonally combined light signal after the combination is returned to the detector 6 through the third port of the polarization beam splitter assembly 2, and the light signal is converted into an electric signal.

[0116] The application provides a polarization beam splitter assembly 2 in an optical path, which has two input ports and two output ports; the first port is an input port, the second port and the fourth port are forward output ports, and the third port is a reverse output port; the first port receives light of an arbitrary polarization state emitted by a light source 1, the second port emits and receives interference signal light passing through a main Y waveguide integrated optical device 3, and the fourth port emits and receives matching reference light passing through a slave waveguide phase modulator 4; the interference signal light and the matching reference light are orthogonally coupled in the polarization beam splitter assembly 2; the third port receives the combined light signal output by the polarization beam splitter assembly 2 after coupling and outputs the combined light signal to a detector 6; the relative intensity noise of the light source is suppressed without changing the circuit and algorithm, the optical path loss is reduced, the signal-to-noise ratio of the fiber optic gyroscope is improved, and the precision of the fiber optic gyroscope is further improved.

[0117] In the technical scheme of the application, the interference signal light and the matching reference light are perpendicular in polarization direction and do not interfere with each other, and only intensity superposition occurs when reaching the detector, so that the influence of the parasitic coherent effect on the precision of the gyroscope can be suppressed.

[0118] The application provides a fiber optic gyroscope optical path design based on double Y waveguide for suppressing the relative intensity noise of a light source, the orthogonal addition compensation effect of the relative intensity noise of the light source can affect and characterize the output precision of the gyroscope, and high output precision of the fiber optic gyroscope can be achieved by achieving good relative intensity noise suppression of the light source.

[0119] The application provides a use method of the fiber optic gyroscope optical path design based on double Y waveguide for suppressing the relative intensity noise of a light source, which comprises the following steps:

[0120] The light source 1 emits light of an arbitrary polarization state, which is transmitted to the polarization beam splitter assembly 2 through the first port of the polarization beam splitter assembly 2 and converted into two mutually orthogonal linearly polarized lights in the polarization beam splitter assembly 2; the two linearly polarized lights are output from the polarization beam splitter assembly 2 through the second port and the fourth port of the polarization beam splitter assembly 2; that is, the polarization beam splitter assembly 2 divides the received linearly polarized signal light into mutually orthogonal signal light and reference light;

[0121] The signal light is transmitted to the main Y waveguide integrated optical device 3 through the second port of the polarization beam splitter assembly 2, and polarization, modulation and beam splitting of the signal light are performed; the signal light after beam splitting is transmitted to the optical fiber sensing ring 5 to propagate clockwise and counterclockwise to sense the Sagnac effect, and then the two signal lights are returned to the main Y waveguide integrated optical device 3 through the optical fiber sensing ring 5 to interfere and combine light, so that interference signal light is obtained; the interference signal light is transmitted to the polarization beam splitter assembly 2 through the second port of the polarization beam splitter assembly 2;

[0122] The reference light is transmitted to the Y waveguide integrated optical device 4 through the fourth port of the polarization beam splitter assembly 2, the reference light is polarized and split, the split reference light is partially depolarized through the two output fiber specific polarization axis angle connections, the partially depolarized reference light returns to the Y waveguide integrated optical device 4 again to combine light and re-polarize, and the matching reference light is obtained, which is transmitted to the polarization beam splitter assembly 2 through the fourth port of the polarization beam splitter assembly 2;

[0123] The interference signal light is reversely input from the second port of the polarization beam splitter assembly 2, and the reference light is reversely input from the fourth port of the polarization beam splitter assembly 2, both of which are linearly polarized light in an orthogonal state, and are coupled and combined in the polarization beam splitter assembly 2; the interference signal light and the matching reference light are coupled in the polarization beam splitter assembly 2 to form an orthogonal combined light signal, which is transmitted to the detector 6 through the third port of the polarization beam splitter assembly 2.

[0124] The specific steps for obtaining the orthogonal combined light signal include:

[0125] ①The output port of the light source 1 is connected to the first port of the polarization beam splitter assembly 2, and the output light in any polarization state is split into linearly polarized and mutually orthogonal signal light and reference light;

[0126] ②The second port of the polarization beam splitter assembly 2 is connected to the input port of the main Y waveguide integrated optical device 3, and the signal light is transmitted to the main Y waveguide integrated optical device 3 for polarization and modulation, and the signal light is split into signal light 1 and signal light 2 through the output end 1 and the output end 2 of the main Y waveguide integrated optical device 3;

[0127] ③The output end 1 and the output end 2 of the main Y waveguide integrated optical device 3 are connected to the two input ends of the fiber sensitive ring 5, and the signal light 1 and the signal light 2 propagate in the clockwise and counterclockwise directions in the fiber sensitive ring 5, respectively, and the signal light 1 and the signal light 2 propagate in the clockwise and counterclockwise directions are sensitive to the Sagnac effect, and the signal light 1 and the signal light 2 propagate in the clockwise and counterclockwise directions return to the main Y waveguide integrated optical device 3 through the fiber sensitive ring 5 again, and combine light interference in the main Y waveguide integrated optical device 3 to obtain the modulated interference signal light I1;

[0128] ④The fourth port of the polarization beam splitter assembly 2 is connected to the polarization maintaining fiber, and the end face is obliquely polished or a small circle is punched to perform high return wave loss processing, and the optical power intensity of the interference signal light obtained by the polarization beam splitter assembly 2 through the third port fiber test is recorded as I1;

[0129] ⑤connecting the fourth port of the polarization beam splitter assembly 2 with the input port of the slave Y waveguide integrated optical device 4, transmitting the reference light to the slave Y waveguide integrated optical device 4 for polarization, and dividing the reference light into reference light 1 and reference light 2 through the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4; connecting the polarization maintaining fiber pigtails of the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4 through a specific axis angle biasing and axis connecting, transmitting and partially depolarizing the reference light 1 and the reference light 2 through the polarization maintaining fiber pigtails of the output port respectively, and then returning to the slave Y waveguide integrated optical device 4 again, re-polarizing through the slave Y waveguide integrated optical device 4 to obtain matching reference light I2;

[0130] ⑥interfering signal light and matching reference light are orthogonally coupled and combined in the polarization beam splitter assembly 2, and the total optical power intensity I0 of the orthogonally combined optical signal of the interfering signal light and the matching reference light obtained through the polarization beam splitter assembly 2 third port pigtail test is recorded as I0, and the axis angle of the polarization maintaining fiber of the output end 1 and the output end 2 of the slave Y waveguide integrated optical device 4 is adjusted to be biased and connected, so that I1≈I2, because I2=I0-I1, actually only I0 needs to be tested, and I0≈2I1 can be met.

[0131]

[0132] ⑧after either of the above two steps is achieved, the polarization beam splitter assembly 2 third port pigtail is connected with the detector 6 pigtail, so that the orthogonally combined optical signal is returned to the detector 6 through the polarization beam splitter assembly 2 third port, and the optical signal is converted into an electrical signal.

[0133] The biasing angle in the application is determined according to the initial modulation depth of the master Y waveguide integrated optical device, and in the example of the application, a large modulation depth corresponds to a biasing angle closer to 90° (a higher depolarization degree) to ensure that the interfering signal light output after the interference of the signal light 1 and the signal light 2 is as equal as possible to the matching reference light output after the combination of the reference light 1 and the reference light 2.

[0134] The application simultaneously uses the modulation depth parameter of the master Y waveguide integrated optical device 3 and the output pigtail biasing angle of the slave Y waveguide integrated optical device 4 to perform accurate control, which can ensure that the interfering signal light and the matching reference light are orthogonal and the optical power is equal,

[0135] ​The signal light and reference light split by the polarization beam splitter assembly of the application will have differences in the transmission process, cannot be completely consistent and orthogonal, and the output light intensity error will cause the noise of the interferometric digital closed-loop fiber optic gyroscope composed of the subsequent main Y waveguide integrated optical device and fiber sensitive ring to change, further affecting the precision of the fiber optic gyroscope, by adjusting the modulation depth parameter of the main Y waveguide integrated optical device in the digital closed-loop system of the fiber optic gyroscope to further compensate the light intensity difference between the interference signal light and the matching reference light, and then reduce the light source relative intensity noise, so that the fiber optic gyroscope has a high output signal-to-noise ratio, thereby improving the output precision of the gyroscope; according to the measured output light intensity values of the interference signal light, the orthogonal synthesized light and the matching reference light, the modulation depth parameter and the off-axis angle are calculated, the modulation depth parameter is used to change the modulated interference signal light, and the off-axis angle is used to change the matching reference light, so that the matching reference light and the modulated interference signal light realize accurate equal light intensity matching.

[0136] The technical scheme of the application designs a polarization beam splitter assembly, cooperates with two Y waveguides, uses the reference light of the idle fourth port of the polarization beam splitter, changes the polarization degree of the polarization light of the reference light route through off-axis butt joint, realizes light intensity matching under the action of the polarization of the slave Y waveguide, makes the output matching reference light and the modulated interference signal light power returned by the main Y waveguide light path accurate, and also greatly reduces the index requirements of optical devices, which is conducive to light intensity cancellation and suppression.

[0137] The technical scheme of the application uses the orthogonal light path addition method, uses the light intensity correlation between the reference light and the signal light emitted by the same light source to cancel noise, realizes the light source relative intensity noise suppression at the eigenfrequency of the fiber optic gyroscope, has good compatibility with the full-digital closed-loop processing technology commonly used by high-precision fiber optic gyroscopes, has strong implementability, does not need to increase or change the hardware design of the modulation and demodulation circuit, greatly reduces the index requirements of optical devices, has a relatively simple debugging process, and has low implementation difficulty.

[0138] Embodiment one

[0139] The self-amplifying radiation light source 1 with a wave band of 1550±30nm is selected; the self-amplifying radiation light source emits light of an arbitrary polarization state;

[0140] The first port of the polarization beam splitter assembly 2 is connected with the self-amplifying radiation light source 1 with a wave band of 1550±30nm; the polarization beam splitter assembly 2 includes a first port, a second port and a fourth port, and a third port;

[0141] The output port of the light source 1 is connected with the first port of the polarization beam splitter assembly 2; the second port of the polarization beam splitter assembly 2 is connected with the input end of the main Y waveguide integrated optical device, and the output end 1 and the output end 2 of the main Y waveguide integrated optical device are respectively connected with the fiber sensing ring 5; the fourth port of the polarization beam splitter assembly 2 is connected with the input end of the slave Y waveguide integrated optical device; the output optical power target splitting ratio of the second port and the fourth port is 1:1, and the output light of the second port and the fourth port is mutually orthogonal linearly polarized light, the second port outputs as a polarization maintaining fiber fast axis output, and the fourth port outputs as a polarization maintaining fiber slow axis output.

[0142] The third port of the polarization beam splitter assembly 2 is connected with the detector 5; as Figure 3 ;

[0143] The polarizer inside the polarization beam splitter assembly 2 is used for converting the received light of any polarization state into linearly polarized light; the polarization beam splitter inside the polarization beam splitter assembly 2 is used for splitting the emitted light signal into mutually orthogonal signal light and reference light; the main Y waveguide integrated optical device 3 performs polarization, splitting and modulation on the signal light, the split signal light returns to the main Y waveguide integrated optical device 3 after propagating through the fiber sensing ring 5 to perform interference and light combination, and the modulated interference signal light is obtained; the slave Y waveguide integrated optical device 4 performs polarization and splitting on the reference light, the split reference light returns to the slave Y waveguide integrated optical device 4 after the polarization is partially removed by the polarization maintaining fiber tail fiber axis misalignment part, and the matching reference light is obtained; the polarization beam splitter inside the polarization beam splitter assembly 2 is used for receiving the returned modulated interference signal light and the matching reference light, and keeping the polarization states orthogonal, and coupling to obtain orthogonal combined light signals; the detector 5 is used for receiving the orthogonal combined light signals output by the polarization beam splitter inside the polarization beam splitter assembly 2.

[0144] The polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the fiber sensing ring 5 and the tail fiber of the detector 6 all adopt polarization maintaining fibers. Among them, the signal light connected by the second port of the polarization beam splitter assembly 2 and the input end of the main Y waveguide integrated optical device 3 is output along the fast axis, and the reference light connected by the fourth port and the input end of the slave Y waveguide integrated optical device 4 is output along the slow axis; wherein when the polarization maintaining fiber is connected, the fourth port of the polarization beam splitter assembly 2 and the tail fiber of the slave Y waveguide integrated optical device 4 are connected at a 90° target axis angle, so that the reference light is changed from the slow axis to the fast axis transmission; the remaining connection points are all connected at a 0° target axis angle, so as to ensure that the interference signal light is transmitted along the fast axis.

[0145] The application also provides a use method of the optical fiber gyroscope optical path design based on the double Y waveguide for suppressing the relative intensity noise of the light source, comprising:

[0146] The light source emits arbitrary polarization state light to the input port of the polarizer, and the arbitrary polarization state light is converted into linear polarization signal light; the linear polarization signal light is transmitted to the polarization maintaining beam splitter through the output port of the polarizer and port 1 of the polarization maintaining beam splitter;

[0147] The polarization maintaining beam splitter assembly divides the received linear polarization signal light into mutually orthogonal signal light and reference light;

[0148] The signal light is transmitted to the main Y waveguide integrated optical device through port 2 of the polarization maintaining beam splitter, and polarization, modulation and beam splitting of the signal light are performed; the beam-splitting signal light is transmitted to the optical fiber sensing ring for transmission and Sagnac effect sensing; the clockwise and counterclockwise transmission signal light returns to the main Y waveguide integrated optical device 4, and polarization, light combination and interference are performed again to obtain interference signal light; the interference signal light is transmitted to the polarization maintaining beam splitter through port 2 of the polarization maintaining beam splitter in the original path;

[0149] The reference light is transmitted to the from Y waveguide integrated optical device through port 4 of the polarization maintaining beam splitter, and polarization and beam splitting of the reference light are performed; the beam-splitting reference light is connected through two polarization maintaining fiber tail fibers with specific polarization axis angles of output port 1 and output port 2 to partially depolarize; the partially depolarized reference light returns to the from Y waveguide integrated optical device to perform light combination and re-polarization to obtain matching reference light; the matching reference light is transmitted to the polarization maintaining beam splitter through port 4 of the polarization beam splitter;

[0150] The interference signal light is reversely input from port 2 of the polarization maintaining beam splitter assembly, and the matching reference light is reversely input from port 4 of the polarization maintaining beam splitter assembly; the two are ideally orthogonal linearly polarized light, and orthogonal coupling and light combination are performed in the polarization maintaining beam splitter to form orthogonal combined light signals, which are transmitted to the detector through port 3 of the polarization maintaining beam splitter.

[0151] The interference signal light is reversely input from the second port of the polarization beam splitter assembly 3, and the reference light is reversely input from the fourth port of the polarization beam splitter assembly 3; the two are ideally orthogonal linearly polarized light, and orthogonal coupling and light combination are performed in the polarization beam splitter assembly 3 to form orthogonal combined light signals, which are finally transmitted to the detector 6 through the third port of the polarization beam splitter assembly 3.

[0152] The technical scheme example of the application uses two Y waveguide integrated optical devices, and a polarization beam splitter assembly composed of a polarizer and a polarization maintaining beam splitter, so that the polarization states of the output interference signal light and the matching reference light are orthogonal, the intensity reaching the detector remains consistent, and the conditions for canceling the coherent intensity noise of the light source by orthogonal addition are met.

[0153] The polarization beam splitter component 2 used in the technical scheme example outputs two output ends to the main Y waveguide integrated optical device, and the light power splitting ratio of the slave Y waveguide integrated optical device is 1:1, and the polarization states are orthogonal; two signal lights output by the main Y waveguide integrated optical device pass through the optical fiber sensitive ring in clockwise and counterclockwise directions respectively, return to the combiner inside the modulator, interfere, and form interference signal light which is transmitted back to the polarization beam splitter component. Two reference lights output by the slave Y waveguide integrated optical device return to the modulator after being connected by the polarization maintaining optical fiber, are re-polarized, form matching reference light which is transmitted back to the polarization beam splitter component, and is orthogonally coupled with the interference signal light of the same source inside the polarization beam splitter, the intensity is superposed, and the noise is cancelled.

[0154] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A fiber optic gyroscope based on dual Y-waveguides to suppress relative intensity noise of a light source, characterized in that, include: The device comprises a light source (1), a polarization beamsplitter assembly (2), a main Y-waveguide integrated optical device (3), a secondary Y-waveguide integrated optical device (4), an optical fiber sensing ring (5), and a detector (6); the polarization beamsplitter assembly (2) includes a first port, a second port, a third port, and a fourth port; the main Y-waveguide integrated optical device (3) includes an input port and an output port 1 and an output port 2; the secondary Y-waveguide integrated optical device (4) includes an input port and an output port 1 and an output port 2. The output end of the light source (1) is connected to the first port of the polarization beamsplitter assembly (2); the second port of the polarization beamsplitter assembly (2) is connected to the input port of the main Y-waveguide integrated optical device (3); the fourth port of the polarization beamsplitter assembly (2) is connected to the input port of the slave Y-waveguide integrated optical device (4); the third port of the polarization beamsplitter assembly (2) is connected to the detector (6); the output ports 1 and 2 of the main Y-waveguide integrated optical device (3) are both connected to the fiber sensing ring (5); the output ports 1 and 2 of the slave Y-waveguide integrated optical device (4) are connected off-axis by a preset alignment angle; the polarization-maintaining fiber pigtail of the input port of the slave Y-waveguide integrated optical device (4) and the fourth port of the polarization beamsplitter assembly (2) are connected by a 90° alignment angle, or by other preset alignment angles.

2. The fiber optic gyroscope according to claim 1, characterized in that, Both the main Y-waveguide integrated optical device (3) and the slave Y-waveguide integrated optical device (4) can only transmit one transmission mode. The main Y-waveguide integrated optical device (3) plays the role of polarization, beam splitting and modulation, while the Y-waveguide integrated optical device (4) plays the role of polarization and beam splitting. The target beam splitting ratio of the optical power of the output ports 1 and 2 of the main Y-waveguide integrated optical device (3) and the slave Y-waveguide integrated optical device (4) is 50:

50. The chip polarization extinction ratio is ≥40dB, the pigtail polarization crosstalk is ≤-20dB, and the backlight reflection is ≤-45dB.

3. The fiber optic gyroscope according to claim 1, characterized in that, The polarization beam splitter assembly (2), the main Y-waveguide integrated optical device (3), the secondary Y-waveguide integrated optical device (4), and the fiber sensing ring (5) are all connected by polarization-maintaining optical fibers; the light source (1) is connected to the polarization beam splitter assembly (2) by ordinary single-mode optical fiber or by polarization-maintaining optical fiber; the detector (6) is connected to the polarization beam splitter assembly (2) by polarization-maintaining optical fiber or by ordinary single-mode optical fiber.

4. The fiber optic gyroscope according to claim 1, characterized in that, The operating wavelengths of the light source (1), polarization beam splitter assembly (2), main Y-waveguide integrated optical device (3), secondary Y-waveguide integrated optical device (4), fiber sensing ring (5), and detector (6) are 850nm, 1310nm, 1550nm, 1550±30nm, 1310±30nm, or 850±30nm.

5. The fiber optic gyroscope according to claim 1, characterized in that, The input and output pigtails of the polarization beam splitter assembly (2), the main Y-waveguide integrated optical device (3), the slave Y-waveguide integrated optical device (4), and the fiber sensing ring (5) are polarization-maintaining fibers.

6. The fiber optic gyroscope according to claim 1, characterized in that, The second and third ports of the polarization beam splitter assembly (2) output mutually orthogonal linearly polarized light; the target output light power ratio of the second and fourth ports of the polarization beam splitter assembly (2) is 50:50, the chip polarization extinction ratio is ≥35dB, the pigtail polarization crosstalk is ≤-25dB, and the backlight reflection is ≤-45dB.

7. The fiber optic gyroscope according to claim 6, characterized in that, If the fourth port of the polarization beam splitter assembly (2) and the polarization-maintaining fiber at the input port of the Y-waveguide integrated optical device (4) are fused at 90° at the connection point, then the Y-waveguide integrated optical device (4) and the main Y-waveguide integrated optical device (3) use polarization-maintaining fibers with the same polarization axis input, that is, both are fast axes or both are slow axes; if the fourth port of the polarization beam splitter assembly (2) and the polarization-maintaining fiber at the input port of the Y-waveguide integrated optical device (4) are fused at 0° at the connection point, then the Y-waveguide integrated optical device (4) and the main Y-waveguide integrated optical device (3) use polarization-maintaining fibers with different polarization axes input, that is, one is a slow axis and the other is a fast axis.

8. The fiber optic gyroscope according to claim 1, characterized in that, The light source (1) emits arbitrary polarization light, which is transmitted to the polarization beamsplitter assembly (2) through the first port of the polarization beamsplitter assembly (2). Within the polarization beamsplitter assembly (2), the arbitrary polarization light is converted into linearly polarized light. The polarization beamsplitter assembly (2) splits the received arbitrary polarization light into mutually orthogonal reference light and signal light. The signal light is transmitted to the main Y-waveguide integrated optical device (3) through the second port of the polarization beamsplitter assembly (2) for polarization, beam splitting, and modulation. The split signal light is then transmitted to the fiber sensing ring (5) to sense the Sagnac effect. The signal light containing sensitive information returns to the main Y-waveguide integrated optical device (3) through the fiber sensing ring (5) for optical combining interference, resulting in interference signal light. The interference signal light is transmitted along the fast axis through the pigtail at the input port of the main Y-waveguide integrated optical device (3), and then returns along the original path from the fast axis to the polarization beamsplitter assembly (2). The reference light is transmitted through the fourth port pigtail of the polarization beamsplitter assembly (2) to the Y-waveguide integrated optical device (4) for reference light polarization and beam splitting. After the beam splitting, the reference light is partially depolarized by the output pigtail according to the set axis angle and then returns to the Y-waveguide integrated optical device (4) for repolarization and matching with the interference signal light to obtain a matched reference light. The matched reference light is transmitted along the fast axis of the polarization-maintaining fiber through the input port pigtail of the Y-waveguide integrated optical device (2), and then deflected by 90° along the fourth port pigtail of the polarization beamsplitter assembly (2) before returning to the polarization beamsplitter assembly (2) from the slow axis. The matched reference light entering along the slow axis through the fourth port of the polarization beamsplitter assembly (2) is orthogonally coupled with the interference signal light entering along the fast axis through the second port to obtain a composite optical signal. The composite optical signal is transmitted through the third port of the polarization beamsplitter assembly (2) to the detector (6) and converted into an electrical signal, which is then processed by the subsequent gyroscope circuit.

9. The fiber optic gyroscope according to claim 8, characterized in that, The target ratio of the optical power of the matching reference light to the interference signal light is 1:1, with a maximum allowable deviation of 20%.

Images