Fiber-optic gyroscope optical path design for inhibiting relative intensity noise of light source based on double Y waveguides

Abstract

According to the fiber-optic gyroscope for suppressing the relative intensity noise of the light source based on the double Y waveguides, interference signal light output by the same light source and noise polarization correlation of matched reference light are utilized, fine adjustment is carried out through the design of the two Y waveguides, so that the output intensity of the two Y waveguides is precisely consistent, polarization states are orthogonal, and the relative intensity noise of the gyroscope light source is suppressed; the precision of the gyroscope is improved; multiple polarization beam splitter assembly light paths are specially designed in a gyroscope light path, polarization state orthogonality and equal-light-intensity light splitting and light combination can be achieved, the specific use method of the gyroscope light path design is further provided, fiber-optic gyroscope homologous interference signal light and matched reference light can specifically meet the adjustment requirements, and the method is suitable for popularization and application. The light source relative intensity noise is effectively reduced, and the output signal-to-noise ratio is improved. The device is simple in design structure, low in implementation difficulty, capable of being finely adjusted, high in adaptability, good in noise suppression effect, suitable for single-axis and multi-axis fiber-optic gyroscopes and also suitable for other fiber-optic sensors with similar optical path structures.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensors such as fiber optic gyroscopes, and particularly relates to an optical path design of a fiber optic gyroscope based on a dual Y waveguide for suppressing the relative intensity noise of a light source. Background Art

[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 startup time, flexible structure design, etc., and is widely used in fields such as land, sea, air, and space. 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 expansion of the inertial navigation field, some new application fields have increasingly higher requirements for the accuracy of fiber optic gyroscopes, which are several times, or even an order of magnitude higher than before.

[0003] In response to the high-precision requirements for fiber optic gyroscopes in new application fields, 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, with relatively low optical power. The accuracy of the fiber optic gyroscope was mainly limited by the shot noise of the light source, and appropriately increasing the light source power did not affect the accuracy of the fiber optic gyroscope. When using an ASE light source with better wavelength stability, the optical power increases significantly by more than an order of magnitude, and the relative intensity noise of the light source becomes the main noise source of the fiber optic gyroscope. Under normal circumstances, the random walk noise of the gyroscope increases synchronously with the light source power, thereby limiting the improvement of the output signal-to-noise ratio and accuracy of the gyroscope. Therefore, an effective method for suppressing the relative intensity noise of the light source needs to be adopted to reduce the random walk noise, improve the output signal-to-noise ratio of the gyroscope, and then improve the output accuracy of the fiber optic gyroscope.

[0004] At present, the methods for suppressing the relative intensity noise of the light source adopted by fiber optic gyroscopes mainly include two technical solutions: the circuit noise subtraction method and the orthogonal optical path addition method. The specific implementation methods have their own characteristics. The former technical solution is represented by the American company AlliedSignal. The main principle is to use two detectors to separately receive the interference signal light and the idle reference light for detection, and then perform electrical signal noise subtraction processing. However, the premise for its effectiveness is that the interference signal light and the idle reference light need to have a very high consistency after being converted into electrical signals, and the performance parameter consistency requirements for the detectors and the subsequent electronic devices are also very high. Otherwise, the noise may increase instead of decreasing, which makes the actual operation very difficult and is not conducive to application and promotion. The technical solution of the orthogonal optical path addition method, represented by the French company Ixblue, mainly aims to make the polarization states of the interference signal light and the idle reference light orthogonal and the optical powers equal, and utilize the polarization correlation of the same-source light to self-suppress the relative intensity noise of the light source, which is more feasible to apply. For this, many implementation solutions have been proposed at home and abroad, but the common feature is that they rely heavily on the special splitting ratio or reflectivity and other static indexes of optical devices. However, the actual values of these indexes are fixed and often have a large deviation from the required values. It is very difficult to achieve the precise matching of the optical powers of the signal light and the reference light through fine adjustment in practice, which affects the suppression effect, and even has the opposite effect, reducing the gyroscope accuracy, and it is also difficult to ensure the consistency of mass production of the gyroscope. Summary of the Invention

[0005] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing a fiber optic gyroscope based on a dual Y waveguide for suppressing the relative intensity noise of the light source, improving the technical solution of suppressing the relative intensity noise by the orthogonal optical path addition method, improving the output signal-to-noise ratio of the fiber optic gyroscope, thereby enhancing the accuracy of the fiber optic gyroscope. At the same time, it also greatly reduces the requirements for parameters such as the splitting ratio and reflectivity of the used optical devices, has a simple operation method, good consistency of debugging results, and is more convenient for engineering mass application.

[0006] The technical solution of the present invention is: a fiber optic gyroscope based on a dual Y waveguide for suppressing the relative intensity noise of the light source, comprising: a light source, a polarization beam splitter assembly, a main Y waveguide integrated optical device, a slave Y waveguide integrated optical device, a fiber optic sensing ring, and a detector; the polarization beam splitter assembly includes a first port, a second port, a third port, and a fourth port; the main Y waveguide integrated optical device includes an input port and output ports 1 and 2; the slave Y waveguide integrated optical device includes an input port and output ports 1 and 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 ports 1 and 2 of the main Y-waveguide integrated optical device are both connected to the fiber optic sensitive loop, and the output ports 1 and 2 of the slave Y-waveguide integrated optical device are offset-connected at a preset axis alignment angle; the input port of the slave Y-waveguide integrated optical device and the polarization-maintaining fiber pigtail of the fourth port of the polarization beam splitter assembly are connected at a 90° axis alignment angle, or are offset-connected at other preset axis alignment angles.

[0008] Both the main Y-waveguide integrated optical device and the slave Y-waveguide integrated optical device can only transmit one transmission mode. Among them, the main Y-waveguide integrated optical device plays the roles of polarization, beam splitting and modulation, and the Y-waveguide integrated optical device plays the roles of polarization and beam splitting; the target optical power splitting ratios of the output ports 1 and 2 of the main Y-waveguide integrated optical device and the slave Y-waveguide integrated optical device are both 50:50, the chip polarization extinction ratio ≥ 40 dB, the pigtail polarization crosstalk ≤ -20 dB; the backward light reflection ≤ -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 optic sensitive loop are all connected by polarization-maintaining fibers; the light source and the polarization beam splitter assembly are connected by a common single-mode fiber or by a polarization-maintaining fiber; the detector and the polarization beam splitter assembly are connected by a polarization-maintaining fiber or by a common single-mode fiber.

[0010] The working bands 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 optic sensitive loop and the detector are in the 850 nm or 1310 nm or 1550 nm or 1550 ± 30 nm or 1310 ± 30 nm or 850 ± 30 nm bands.

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

[0012] The outputs of the second port and the third port of the polarization beam splitter assembly are linearly polarized lights that are orthogonal to each other; the target output optical power ratio between the second port and the fourth port of the polarization beam splitter assembly is 50:50, the chip polarization extinction ratio ≥ 35 dB, the pigtail polarization crosstalk ≤ -25 dB; the backward light reflection ≤ -45 dB.

[0013] If the fourth port of the polarization beam splitter assembly is butt-welded at a 90° angle with the polarization-maintaining fiber at the input port of the slave Y-waveguide integrated optical device, the slave Y-waveguide integrated optical device and the master Y-waveguide integrated optical device use the same type of polarization axis input of the polarization-maintaining fiber, that is, both are the fast axis or both are the slow axis; if the fourth port of the polarization beam splitter assembly is butt-welded at a 0° angle with the polarization-maintaining fiber at the input port of the slave Y-waveguide integrated optical device, the slave Y-waveguide integrated optical device and the master Y-waveguide integrated optical device use different types of polarization axis input of the polarization-maintaining fiber, that is, one is the slow axis and the other is the fast axis.

[0014] Including: the light source emits light with an arbitrary polarization state and transmits it to the polarization beam splitter assembly through the first port of the polarization beam splitter assembly. Inside the polarization beam splitter assembly, the light with an arbitrary polarization state is converted into linearly polarized light; the polarization beam splitter assembly splits the received light with an arbitrary polarization state into mutually orthogonal reference light and signal light; the signal light is transmitted to the master Y-waveguide integrated optical device through the second port of the polarization beam splitter assembly, where the signal light is polarized, split, and modulated. The split signal light is transmitted into the fiber optic sensing ring to sense the Sagnac effect. The signal light containing sensitive information returns to the master Y-waveguide integrated optical device through the fiber optic sensing ring again for optical combination and interference to obtain an interference signal light; the interference signal light is transmitted along the fast axis through the pigtail at the input port of the master Y-waveguide integrated optical device, and then returns along the pigtail at the second port of the polarization beam splitter assembly along the original path and is transmitted to the polarization beam splitter assembly from the fast axis; the reference light is transmitted to the slave Y-waveguide integrated optical device through the pigtail at the fourth port of the polarization beam splitter assembly, where the reference light is polarized and split. After the split reference light is partially depolarized by being axially offset-connected at a set angle through the output pigtail, it returns to the slave Y-waveguide integrated optical device for re-polarization and is matched 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 pigtail at the input port of the slave Y-waveguide integrated optical device, and then deflects 90° along the pigtail at the fourth port of the polarization beam splitter assembly and returns from the slow axis to be transmitted into the polarization beam splitter assembly; the matched reference light entering along the slow axis through the fourth port of the polarization beam splitter assembly is orthogonally coupled with the interference signal light entering along the fast axis through the second port to obtain a combined optical signal; the combined optical signal is transmitted to the detector through the third port of the polarization beam splitter assembly and converted into an electrical signal, which is then processed by the subsequent gyro circuit part.

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

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

[0017] (1) In the optical path of the fiber optic gyroscope of the present invention, by utilizing the optical intensity correlation between the homologous reference light and the signal light, and adding a Y waveguide optical integration device, the output polarized light is partially depolarized and then re-polarized, so that the optical intensity consistency between the matched output reference light and the interference light is better and the matching degree is higher, maximizing the cancellation of the relative intensity noise of the light source, thereby further improving the output accuracy of the fiber optic gyroscope;

[0018] (2) The optical path structure of the fiber optic gyroscope of the present invention is simple, uses standardized general components, relaxes the requirements for the static parameter indicators of optical components, reduces the production cost, and is conducive to mass production;

[0019] (3) The method of using the optical path design for suppressing the relative intensity noise of the light source in the present invention can achieve refined dynamic adjustment of the degree of suppression of the relative intensity noise of the light source, with low difficulty in achieving the target result, better effect, and being more conducive to engineering batch applications. Description of the Drawings

[0020] Figure 1 Schematic diagram of the existing design scheme for suppressing the relative intensity noise of the light source of the fiber optic gyroscope based on the circuit noise subtraction method;

[0021] Figure 2 Schematic diagram of the existing design scheme for suppressing the relative intensity noise of the light source of the fiber optic gyroscope based on the orthogonal optical path addition method;

[0022] Figure 3 Schematic diagram of the optical path design scheme of the fiber optic gyroscope for suppressing the relative intensity noise of the light source based on the double Y waveguide of the present invention;

[0023] Figures 4 - 9 Schematic diagram of various possible schemes of the polarization beam splitter assembly using the scheme of the present invention. Detailed Embodiments

[0024] The present invention provides a fiber optic gyroscope for suppressing the relative intensity noise of the light source based on a double Y waveguide, including: 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 optic sensing ring 5, and a detector 6.

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

[0026] An exemplary light source 1 of the present invention is an ASE self-amplified spontaneous emission light source, and the ASE self-amplified spontaneous emission light source emits light with an arbitrary polarization state;

[0027] The working bands of the light source 1, polarization beam splitter assembly 2, main Y waveguide integrated optical device 3, slave Y waveguide integrated optical device 4, fiber optic sensing loop 5, and detector 6 can be the commonly used bands of 850 nm, 1310 nm, and 1550 nm for fiber optic gyroscopes; further, the band of the ASE self-amplified spontaneous emission light source used in the optical path is 1550 ± 30 nm; the bands of the superluminescent SLD light source used in the optical path are 1310 ± 30 nm and 850 ± 30 nm; in the exemplary embodiment of the present invention, the band of the ASE self-amplified spontaneous emission light source is 1550 ± 30 nm;

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

[0029] The light source 1, polarization beam splitter assembly 2, main Y waveguide integrated optical device 3, slave Y waveguide integrated optical device 4, fiber optic sensing loop 5, and detector 6 are all 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 optic sensing loop 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 pigtails of the polarization beam splitter assembly 2, main Y waveguide integrated optical device 3, slave Y waveguide integrated optical device 4, and fiber optic sensing loop 5 can be the commonly used PANDA polarization-maintaining optical fibers, or other bow-tie, tiger-type, elliptical cladding, one-type polarization-maintaining optical fibers, and the cladding diameter can be common specifications such as φ125 μm, φ80 μm, φ60 μm, etc., or special specifications such as φ50 μm, φ40 μm, etc.; in the exemplary embodiment of the present invention, the connecting optical fiber uses a PANDA polarization-maintaining optical fiber with a cladding diameter of φ80 μm;

[0032] In the embodiment of the present invention, for the PANDA polarization-maintaining optical fiber, the polarization axis includes a fast axis and a slow axis, and the effective refractive indices in the directions of the fast axis and the slow axis are different, and the light propagation speeds are different. It can be known that the slow axis in the PANDA optical fiber passes horizontally through the panda's eyes, and the fast axis is perpendicular to the slow axis passing through the center; in the embodiment of the present invention, without special instructions, the linearly polarized light initially propagates along the fast axis. When the polarization-maintaining optical fibers are connected at different ports, the polarization axis rotates 90°, and the linearly polarized light will change from the fast axis to propagate along the slow axis; if the linearly polarized light initially propagates along the slow axis, when the polarization-maintaining optical fibers are connected at different ports, the polarization axis rotates 90°, and the linearly polarized light will change from the slow axis to propagate along the fast 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 optic 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; the third port of the polarization beam splitter assembly 2 is connected to the input end of the detector 6, see attached Figure 3 。

[0034] The polarization beam splitter assembly 2 is used to convert light with 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 that propagate back respectively; the main Y waveguide integrated optical device 3 polarizes, splits, and modulates the signal light, and then the two beams of signal light propagate through the fiber optic sensing ring 5 and return to the main Y waveguide integrated optical device 3 for interference and light combination to obtain interference signal light; the slave Y waveguide integrated optical device 4 polarizes and splits the reference light, and then the two beams of reference light are partially depolarized after being connected at a special angle through polarization-maintaining pigtails and return to the slave Y waveguide integrated optical device 4 for re-polarization to obtain a matching reference light with the same light intensity as the interference signal light.

[0035] The polarization beam splitter assembly 2 is used to receive the interference signal light and the matching reference light, and perform orthogonal coupling to obtain an orthogonally combined optical signal; the detector 6 is used to receive the orthogonally combined optical signal output by the polarization beam splitter assembly 2; 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] After the main Y waveguide integrated optical device 3 polarizes, modulates, and equally splits the signal light, two beams of interference signal light enter the fiber optic sensing ring 5 to propagate, and finally return to the main Y waveguide integrated optical device 3 for beam combination interference, and then the interference signal light is transmitted to the polarization beam splitter assembly 2. The two beams of interference signal light are modulated by the peripheral circuit signal, and the modulation depth of the circuit signal can be used to modulate the interference situation of the two beams of interference light in the main Y waveguide integrated optical device 4 to adjust the light intensity, and the modulation depth can be selected between [π / 2, π).

[0038] The target output optical power ratio of the second port to the fourth port of the polarization beam splitter assembly 2 is 50:50; the target output optical 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 20 dB;

[0040] The orthogonally output linear polarized lights at the second port and the fourth port of the polarization beam splitter component 2 propagate along the fast axis and the slow axis of their respective pigtails, see the appendix Figure 3 ;

[0041] The polarization beam splitter component 2 used in the exemplary technical solution of the present invention has a structure as shown in the appendix Figure 4 . The polarization beam splitter component 2 can have the following other structures, see the appendix Figure 5 , appendix Figure 6 , appendix Figure 7 , appendix Figure 8 , appendix Figure 9 ;

[0042] In the exemplary technical solution of the present invention, the second port of the polarization beam splitter component 2 is connected to the input port of the main Y waveguide integrated optical device 3 to receive the interferometric signal light that returns from the fiber optic sensing ring 5 and is modulated. The fourth port is connected to the input port of the slave Y waveguide integrated optical device 4 to receive the matching reference light that is connected to the output pigtail of the slave Y waveguide integrated optical device 4 in an off-axis manner and is repolarized and returned. The interferometric signal light and the matching reference light are orthogonally coupled in the polarization beam splitter component 2 and superposed in intensity, so that the intensity reaching the detector 6 is kept consistent, meeting the condition of cancellation and suppression of the coherent intensity noise of the light source by the orthogonal addition method.

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

[0044] In the technical solution of the present invention, the target value of the optical power splitting ratio of the two output ends of the main Y waveguide integrated optical device 3 is 50:50. The two output signal lights pass through the fiber optic sensing ring 5 and propagate in the clockwise and counterclockwise directions respectively, and then return to the inside of the main Y waveguide integrated optical device 3 to be combined, and interference occurs. The formed interferometric signal light returns to the polarization beam splitter component 2 along the original path.

[0045] In the technical solution of the present invention, the target value of the optical power splitting ratio of the two output ends of the slave Y waveguide integrated optical device 4 is 50:50. The two output optical signals pass through off-axis docking and then return to the inside of the slave Y waveguide integrated optical device in the clockwise and counterclockwise directions respectively to be combined. After repolarization and filtering, the formed matching reference light returns to the polarization beam splitter component 2 along the original path.

[0046] In the exemplary embodiment of the present invention, the pigtail of the ASE self-amplified spontaneous emission light source is a single-mode fiber, and the pigtails of the polarization beam splitter component 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, the fiber optic sensing ring 5, and the detector 6 all use polarization-maintaining fibers;

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

[0048] If the input ends of the two Y waveguide integrated optical devices are both slow-axis inputs, the polarization-maintaining pigtail at the input end of the output port of the polarization beam splitting component 2 with fast-axis output and the pigtail at the input end of the Y waveguide integrated optical device should be correspondingly adjusted to be connected at a target alignment angle of 90°;

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

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

[0051] In the embodiments of the present invention, 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 inputs and fast-axis outputs. Among them, when connecting the polarization-maintaining optical fiber, the pigtail at the connection between the second port (fast-axis output) of the polarization beam splitter assembly 2 and the input port of the main Y waveguide integrated optical device 3 is connected with 0° axis alignment. The connection points between the output port of the main Y waveguide integrated optical device 3 and the optical fiber sensing ring 5 are all connected with 0° to ensure that the interference optical signal is transmitted along the fast axis. The pigtail 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 with 90° axis alignment, so that the reference light is transmitted along the pigtail from the slow axis to the fast axis. The pigtails of the output port 1 and the output port 2 of the slave Y waveguide integrated optical device 4 are connected with a special axis alignment angle. The target axis alignment angle ranges from 50° to 90°, and the actual value will deviate slightly from the reference value in the table. The axis alignment angle is related to indicators such as the modulation depth parameter and the Y waveguide insertion loss, and the corresponding relationship needs to be accurately determined through experimental measurement. The returned reference light is re-polarized in the fast-axis direction at the input port of the slave Y waveguide integrated optical device 4, and then transmitted along the pigtail and converted from the fast axis to the slow axis at the connection point with the fourth port of the polarization beam splitter assembly 2 and returns to the polarization beam splitter assembly 2.

[0052] In actual production, after connecting the optical path, the modulation depth parameter can be fixed first. Disconnect the fourth port of the polarization beam splitter assembly 2, process the pigtail well, and measure the output power of the third port of the polarization beam splitter assembly 2. Disconnect the second port of the polarization beam splitter assembly 2, process the pigtail well, and reconnect the pigtail between the input port of the slave Y waveguide integrated optical device 4 and the fourth port of the polarization beam splitter assembly 2 at different axis alignment angles, and measure the output power of the third port of the polarization beam splitter assembly 2 until the two powers are approximately equal, and record the off-axis angle θ. In this way, an accurate correspondence table between the modulation depth and the axis alignment angle is established to guide the subsequent off-axis connection of the optical path pigtail. The initial reference value of the axis alignment angle is shown in Table 1.

[0053] Table 1 Corresponding table of reference values of several typical modulation depth parameters and off-axis angle θ

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

[0055] Note: For other modulation depths, the corresponding reference initial off-axis angles can be selected from the corresponding intervals on both sides of the table, with a maximum not exceeding 90°.

[0056] In the technical solution of the present invention, the polarization beam splitter assembly 2 divides the optical signal output by the light source 1 into two beams. One beam is the signal light transmitted along the output pigtail of the second port (fast axis of the polarization-maintaining fiber), and the other beam is the reference light transmitted along the output pigtail of the fourth port (slow axis of the polarization-maintaining fiber). The signal light is transmitted through the second port of the polarization beam splitter assembly 2 to the main Y-waveguide integrated optical device 3. The signal light is divided into signal light 1 and signal light 2 through the output end 1 and output end 2 of the main Y-waveguide integrated optical device 3. The signal light 1 and signal light 2 respectively enter the fiber optic sensing ring 5, and the signal light 1 and signal light 2 respectively propagate in the fiber optic sensing ring 5 in the counterclockwise and clockwise directions to sense the Sagnac effect. The reference light is transmitted through the fourth port of the polarization beam splitter assembly 2 to the slave Y-waveguide integrated optical device 4. The reference light is divided into reference light 1 and reference light 2 through the output end 1 and output end 2 of the slave Y-waveguide integrated optical device 4. The reference light 1 and reference light 2 are each transmitted through a polarization-maintaining fiber pigtail and are butt-jointed at a specific axis alignment angle. The axis alignment angle depends on the modulation depth applied to the main Y-waveguide integrated optical device 3 by the peripheral circuit signal. A larger modulation depth corresponds to an axis alignment angle closer to 90°. See Table 1, so as to ensure that the interference signal light output after the interference of the signal light 1 and signal light 2 is as equal as possible to the matching reference light output after the polarization of the combination of the reference light 1 and reference light 2. The interference signal light and the matching reference light are orthogonally coupled and combined in the polarization beam splitter assembly 2. The orthogonally combined optical signal after combination is then returned to the detector 6 through the third port of the polarization beam splitter assembly 2, and the optical signal is converted into an electrical signal. Thus, the suppression of the relative intensity noise of the light source is achieved without changing the circuit and algorithm, reducing the optical path loss, improving the signal-to-noise ratio of the fiber optic gyroscope, and further improving the accuracy of the fiber optic gyroscope.

[0057] In the technical solution of the present invention, the polarization directions of the interference signal light and the matching reference light are perpendicular and do not interfere. Only intensity superposition occurs when reaching the detector, thereby suppressing the influence of parasitic coherence effects on the accuracy of the gyroscope.

[0058] A fiber optic gyroscope optical path design based on a dual Y-waveguide for suppressing the relative intensity noise of the light source proposed by the present invention. The relative intensity noise of the light source can affect and characterize the output accuracy of the gyroscope through the orthogonal addition compensation effect of the fiber. By achieving good suppression of the relative intensity noise of the light source, a higher output accuracy of the fiber optic gyroscope can be realized.

[0059] In the optical path provided by the present invention, a polarization beam splitter assembly 2 is designed, which has two input ports and two output ports. Among them, the first port is the input port, the second port and the fourth port are the forward output ports, and the third port is the reverse output port. The first port receives light with any polarization state emitted by the light source 1. The second port emits and receives (through the main Y waveguide integrated optical device 3) the signal light, and the fourth port emits and receives (through the slave waveguide phase modulator 4) the reference light. Moreover, the signal light and the reference light emitted and received by the first port and the fourth port are linearly polarized lights orthogonal to each other. The returned interference signal light and the matching reference light are orthogonally coupled in the polarization beam splitter assembly 2. The third port receives the orthogonally combined optical signal output (detector 6) after coupling by the polarization beam splitter assembly 2.

[0060] In the optical path provided by the present invention, the composition of the polarization beam splitter assembly 2 is also designed. This assembly has two input ports and two output ports. Among them, the pigtails connected to the second port and the fourth port must be polarization-maintaining fibers, and the pigtails connected to the remaining ports can be polarization-maintaining fibers or single-mode fibers, depending on the internal composition of the polarization beam splitter assembly. The assembly can be a combination of two discrete functional devices or an integrated combination of functional devices, and generally has six typical structures. See the appendix Figure 4 and the appendix Figure 5 and the appendix Figure 6 and the appendix Figure 7 and the appendix Figure 8 and the appendix Figure 9 .

[0061] Among them, for Structure 1, the polarization beam splitter assembly 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 assembly, receives light with any polarization state output by the 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. Port 2 and port 4 of the polarization-maintaining beam splitter serve as the forward output ports of the polarization beam splitter assembly - the second port and the fourth port, and split the linearly polarized light into linearly polarized lights with a splitting ratio target value of 50:50 and orthogonal to each other, which are respectively output from port 2 and port 4 of the polarization-maintaining beam splitter. The mutually orthogonal linearly polarized lights returned from port 2 and port 4 of the polarization-maintaining beam splitter are input into the polarization-maintaining beam splitter, and after orthogonal coupling, they are combined and output at port 3 of the polarization-maintaining beam splitter. Port 3 of the polarization-maintaining beam splitter serves as the third port of the polarization beam splitter assembly. In this structure, the pigtails of the polarizer and the 2×2 polarization-maintaining beam splitter are both polarization-maintaining fibers, and the pigtail of the connected detector is preferably a polarization-maintaining fiber, and the pigtail of the connected light source can be a single-mode fiber.

[0062] Among them, in Structure 2, the polarization beam splitter component is composed of a 3-port polarization-maintaining circulator and a 1×2 fiber polarization beam splitter / combiner. Port 1 (input end) of the polarization-maintaining circulator serves as the first port of the polarization beam splitter component, receiving light with any polarization state output by the light source. Port 2 (forward input, reverse output end) of the polarization-maintaining circulator is connected to Port III (beam splitting input end, beam combining output end) of the 1×2 fiber polarization beam splitter / combiner, polarizing the forward output light of the polarization-maintaining circulator into linearly polarized light and inputting it into the fiber polarization beam splitter / combiner. At the same time, the input light is split into linearly polarized lights with a target splitting ratio of 50:50 and orthogonal to each other, and is output from Port I and Port II of the fiber polarization beam splitter / combiner respectively. Port I and Port II of the fiber polarization beam splitter / combiner serve as the forward output ports - the second port and the fourth port of the polarization beam splitter component. The mutually orthogonal linearly polarized lights returned from Port I and Port II of the fiber polarization beam splitter / combiner are input into the fiber polarization beam splitter / combiner for orthogonal coupling, and then are combined and output at Port III of the fiber polarization beam splitter / combiner. Port III of the fiber polarization beam splitter / combiner is connected to Port 2 (forward input, reverse output end) of the polarization-maintaining fiber circulator, and finally is output from Port 3 (output end) of the polarization-maintaining fiber circulator. Port 3 of the polarization-maintaining fiber circulator serves as the third port of the polarization beam splitter component. In this structure, the pigtails of the 1×2 fiber polarization beam splitter and the polarization-maintaining circulator are both polarization-maintaining fibers. The pigtail of the connected detector is preferably a polarization-maintaining fiber, and can also be a single-mode fiber. The pigtail of the connected light source is a single-mode fiber.

[0063] Among them, in Structure 3, the polarization beam splitter component is composed of a 3-port fiber optic sensitive circulator and a 1×2 fiber optic polarization beam splitter / combiner. Port 1 (input end) of the fiber optic sensitive circulator serves as the first port of the polarization beam splitter component, receiving light with any polarization state output by the light source. Port 2 (forward input, reverse output end) of the fiber optic sensitive circulator is connected to Port III (beam splitting input end, beam combining output end) of the 1×2 fiber optic polarization beam splitter / combiner, inputting the forward output light of the fiber optic sensitive circulator into the fiber optic polarization beam splitter / combiner, and at the same time splitting the input light into linearly polarized lights with a target splitting ratio of 50:50 and orthogonal to each other, which are output from Port I and Port II of the fiber optic polarization beam splitter / combiner respectively; Port I and Port II of the fiber optic polarization beam splitter / combiner serve as the forward output ports of the polarization beam splitter component - the second port and the fourth port. The linearly polarized lights orthogonal to each other returned from Port I and Port II of the fiber optic polarization beam splitter / combiner are input into the fiber optic polarization beam splitter / combiner for orthogonal coupling and then combined and output at Port III of the fiber optic polarization beam splitter / combiner. Port III of the fiber optic polarization beam splitter / combiner is connected to Port 2 (forward input, reverse output end) of the fiber optic circulator, and finally output from Port 3 (output end) of the fiber optic circulator. Port 3 of the fiber optic circulator serves as the third port of the polarization beam splitter component; in this structure, the pigtails of Port I and Port II of the 1×2 fiber optic polarization beam splitter / combiner are polarization maintaining fibers, the pigtail of Port III can be a common fiber or a polarization maintaining fiber, and the pigtail of the fiber optic circulator is a single mode fiber; the pigtails of the connected detectors and light sources are single mode fibers.

[0064] Among them, for Structure 4, the polarization beam splitter assembly is composed of a 4-port fiber optic splitter and a 1×2 fiber optic polarization beam splitter / combiner. Port 1 (input end) of the fiber optic splitter serves as the first port of the polarization beam splitter assembly, receiving light with any polarization state output by the light source. Port 2 (forward input, reverse output end) of the fiber optic splitter is connected to Port III (beam splitting input end, beam combining output end) of the 1×2 fiber optic polarization beam splitter / combiner, inputting the forward output light of the fiber optic splitter into the fiber optic polarization beam splitter / combiner. Meanwhile, the input light is split into linearly polarized lights with a target splitting ratio of 50:50 and orthogonal to each other, and is output from Port I and Port II of the fiber optic polarization beam splitter / combiner respectively. Port I and Port II of the fiber optic polarization beam splitter / combiner serve as the forward output ports - the second port and the fourth port of the polarization beam splitter assembly. The orthogonal linearly polarized lights returned from Port I and Port II of the fiber optic polarization beam splitter / combiner are input into the fiber optic polarization beam splitter / combiner for orthogonal coupling, and then are combined and output at Port III of the fiber optic polarization beam splitter / combiner. Port III of the fiber optic polarization beam splitter / combiner is connected to Port 2 (forward input, reverse output end) of the fiber optic splitter, and finally is output from Port 3 (output end) of the fiber optic splitter. Port 3 of the fiber optic splitter serves as the third port of the polarization beam splitter assembly. Port 4 of the fiber optic splitter is treated as a vacant end by measures such as oblique throwing or making small coils to increase the return loss. In this structure, the pigtails of Port I and Port II of the 1×2 fiber optic polarization beam splitter / combiner are polarization-maintaining fibers, the pigtail of Port III of the fiber optic polarization beam splitter / combiner and the pigtails of the fiber optic splitter can be single-mode fibers, and the pigtails connected to the light source and the detector are single-mode fibers.

[0065] The present invention also provides a usage method for an optical fiber gyroscope optical path design based on a dual Y waveguide to suppress the relative intensity noise of a light source, including:

[0066] The light source 1 emits light with any polarization state and transmits it through the first port of the polarization beam splitter assembly 2 into the polarization beam splitter assembly 2, converting the light with any polarization state into two orthogonally polarized light beams; the two linearly polarized light beams are respectively output from the polarization beam splitter assembly 2 through the second port and the fourth port of the polarization beam splitter assembly; that is, the polarization beam splitter assembly 2 divides the received linearly polarized signal light into orthogonal signal light and reference light.

[0067] The signal light is transmitted through the second port of the polarization beam splitter assembly 2 into the main Y waveguide integrated optical device 3, where the signal light is polarized, modulated, and split. The split signal light is transmitted into the fiber optic sensitive ring 5 for forward and reverse propagation to sense the Sagnac effect. Then the two signal light beams return to the main Y waveguide integrated optical device 3 again through the fiber optic sensitive ring 5 for interference and beam combination, obtaining an interference signal light. The interference signal light is transmitted through the second port of the polarization beam splitter assembly 2 into the polarization beam splitter assembly 2.

[0068] The reference light is transmitted into the slave Y waveguide integrated optical device 4 through the fourth port of the polarization beam splitter assembly 2 for polarization and beam splitting of the reference light. The split reference light is partially depolarized through specific off-axis angle connections of two pigtails at the output end, and the partially depolarized reference light returns to the slave Y waveguide integrated optical device 4 again for light combination and re-polarization to obtain a matching reference light. The matching reference light is transmitted into the polarization beam splitter assembly 2 through the fourth port of the polarization beam splitter assembly 2;

[0069] 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. The two are ideally orthogonal linearly polarized lights and are orthogonally coupled inside the polarization beam splitter assembly 2 to synthesize an optical signal; inside the polarization beam splitter assembly 2, the interference signal light and the matching reference light are coupled to form an orthogonal synthesized optical signal, which is transmitted to the detector 6 through the third port of the polarization beam splitter assembly 2.

[0070] The specific steps of the orthogonally coupled synthesized optical signal 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 light of any polarization state is output and split into a signal light and a reference light that are linearly polarized and 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, and transmit the signal light 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 output end 1 and output end 2 of the main Y waveguide integrated optical device 3;

[0073] ③ The output end 1 and output end 2 of the main Y waveguide integrated optical device 3 are connected to the two input ends of the fiber optic sensing ring 5, and signal light 1 and signal light 2 propagate in the fiber optic sensing ring 5 in the clockwise and counterclockwise directions respectively, sensing the Sagnac effect. The signal light 1 and signal light 2 propagating in the clockwise and counterclockwise directions return to the main Y waveguide integrated optical device 3 again through the fiber optic sensing ring 5, and light combination interference is performed in the main Y waveguide integrated optical device 3 to obtain the modulated interference signal light I 1 ;

[0074] ④ After the end face of the polarization maintaining pigtail of the fourth port of the polarization beam splitter assembly 2 is obliquely polished or looped to perform high return loss treatment, the optical power intensity of the interference signal light obtained by testing the pigtail of the third port of the polarization beam splitter assembly 2 is denoted as I 1 ;

[0075] ⑤ Connect the fourth port of the polarization beam splitter component 2 with the input port of the slave Y-waveguide integrated optical device 4, transmit the reference light to the slave Y-waveguide integrated optical device 4 for polarization, and divide 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; dock the polarization-maintaining optical fiber pigtails of the output end 1 and the output end 2 of the slave Y-waveguide integrated optical device 4 at a specific axis angle, so that the reference light 1 and the reference light 2 are respectively transmitted through the polarization-maintaining optical fiber pigtails of the output port and partially depolarized, and then return to the slave Y-waveguide integrated optical device 4 again, and re-polarize through the slave Y-waveguide integrated optical device 4 to obtain the matching reference light I 2 ;

[0076] ⑥ The interference signal light and the matching reference light are orthogonally coupled and combined in the polarization beam splitter component 2, and the total optical power intensity I of the orthogonal composite optical signal of the interference signal light and the matching reference light obtained by the third port pigtail test of the polarization beam splitter component 2 is 0 , denoted as I 0 , adjust the axis angle of the polarization-maintaining optical fiber at the output end 1 and the output end 2 of the Y-waveguide integrated optical device 4 to be off-axis docked, so that I 1 ≈I 2 , because I 2 =I 0 -I 1 In fact, only the test I 0 , satisfying I 0 ≈2I 1 That's it.

[0077] ⑦ If the previous step is difficult to achieve I 0 ≈2I 1 , then adjust the modulation depth of the modulation signal of the peripheral circuit, and simultaneously measure the total optical power intensity I of the new orthogonal synthesized optical signal 0 ', until I 0 ′=2(I 0 -I 1 );

[0078] ⑧ After any of the above two steps is achieved, the pigtail of the third port of the polarization beam splitter component 2 is connected to the pigtail of the detector 6, so that the orthogonal synthesized optical signal returns to the detector 6 through the third port of the polarization beam splitter component 2, and the optical signal is converted into an electrical signal.

[0079] The off-axis angle described in the present invention is determined by the initial modulation depth of the main Y-waveguide integrated optical device. In the example of the present invention, a larger modulation depth corresponds to an off-axis angle closer to 90° (a higher degree of depolarization) to ensure that the interference signal light output after the interference of signal light 1 and signal light 2 is as equal as possible to the matching reference light output after the synthesis of reference light 1 and reference light 2 and re-polarization.

[0080] The present invention uses two different parameters, namely, the modulation depth of the main Y-waveguide integrated optical device 3 and the output pigtail off-axis angle of the slave Y-waveguide integrated optical device 4, for precise control simultaneously, which can ensure that the interfering signal light and the matching reference light are orthogonal and have equal optical power.

[0081] For the signal light and the reference light split by the polarization beam splitter assembly of the present invention, differences will occur during the transmission process, and they cannot be completely consistent and orthogonal. The output optical intensity error will cause changes in the noise of the interferometric digital closed-loop fiber optic gyroscope composed of the subsequent main Y-waveguide integrated optical device and the fiber optic sensitive ring, further affecting the accuracy of the fiber optic gyroscope. By adjusting the modulation depth of the main Y-waveguide integrated optical device in the fiber optic gyroscope digital closed-loop system to further compensate for the optical intensity difference between the interfering signal light and the matching reference light, the relative intensity noise of the light source is reduced, enabling the fiber optic gyroscope to have a high output signal-to-noise ratio, thereby improving the output accuracy of the gyroscope; according to the measured output optical intensity values of the interfering signal light, the quadrature composite light, and the matching reference light, the modulation depth and the off-axis angle are calculated, the modulated interfering signal light is changed using the modulation depth, and the matching reference light is changed using the off-axis angle to achieve precise equal optical intensity matching between the matching reference light and the modulated interfering signal light.

[0082] The technical solution of the present invention designs a polarization beam splitter assembly, which cooperates with the main and slave Y-waveguides. By using the reference light from the idle fourth port of the polarization beam splitter and through off-axis docking, the polarization degree of the linearly polarized light in the reference light path changes, and under the re-polarization effect of the slave Y-waveguide, the optical intensity ratio is achieved, making the output matching reference light have exactly the same optical power as the modulated interfering signal light returned from the main Y-waveguide optical path. At the same time, the requirements for the indexes of optical devices are also greatly reduced, which is beneficial to the cancellation and suppression of orthogonal light.

[0083] The technical solution of the present invention uses the orthogonal optical path addition method to suppress the relative intensity noise of the light source at the intrinsic frequency of the fiber optic gyroscope by using the optical intensity correlation between the reference light and the signal light emitted from the same light source. It has good compatibility with the all-digital closed-loop processing technology commonly used in high-precision fiber optic gyroscopes, strong feasibility, does not require additional hardware design to increase or change the modulation and demodulation circuit, greatly reduces the requirements for the indexes of optical devices, has a relatively simple debugging process, and low implementation difficulty.

[0084] A specific embodiment of the present invention, such as Figure 3 , discloses an optical path design of a fiber optic gyroscope for suppressing the relative intensity noise of the light source based on a dual Y-waveguide. To illustrate the effectiveness of the method proposed by the present invention, the above technical solutions of the present invention are described in detail through specific embodiments as follows. The specific implementation steps are as follows:

[0085] The present invention provides an optical path design for an optical fiber gyroscope based on a dual Y waveguide to suppress the relative intensity noise of a light source, including: 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 sensing 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 optical fiber sensing ring 5, and the detector 6 are all connected by optical fibers;

[0087] The light source 1 is a self-amplified spontaneous emission (ASE) light source;

[0088] The light source 1 is connected to the polarization beam splitter assembly 2 by a single-mode optical fiber, and the polarization beam splitter assembly 2, the main Y waveguide integrated optical device 3, the slave Y waveguide integrated optical device 4, and the optical fiber sensing ring 5 are all connected by polarization-maintaining optical fibers; the detector 6 can be connected to 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 by a pigtail;

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

[0090] In an embodiment of the present invention, the first port of the polarization beam splitter assembly 2 is connected to the ASE self-amplified spontaneous emission light source 1; the ASE self-amplified spontaneous emission light source emits light with an arbitrary polarization state;

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

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

[0093] The polarization beam splitter assembly 2 is used to convert the received light with an arbitrary polarization state into linearly polarized light; the polarization beam splitter assembly 2 is used to divide the output optical signal into two mutually orthogonal reference light and signal light and transmit them bidirectionally; the main Y waveguide integrated optical device 3 polarizes, modulates, and splits the signal light. The split signal light returns to the main Y waveguide integrated optical device 3 after passing through the optical fiber sensing ring 5 for interference and beam combination to obtain a modulated interference optical signal;

[0094] The reference light is polarized and split by the integrated optical device 4 of the Y waveguide. After the polarization of the split reference light is depolarized by the off-axis butt joint part of the polarization-maintaining fiber pigtail, it returns to the integrated optical device 4 of the Y waveguide again for repolarization to obtain a matched reference light;

[0095] The polarization beam splitter assembly 2 is used to receive the returned modulated interference light and the matched reference light. The two are linearly polarized lights orthogonal to each other. After coupling and combining, an orthogonally synthesized optical signal is obtained; the detector 5 is used to receive the orthogonally synthesized optical signal output by the polarization beam splitter assembly 2.

[0096] The target optical power ratio of the modulated interference light to the matched reference light is: 1:1;

[0097] The main integrated optical device 3 of the Y waveguide splits and modulates the signal light by 50:50 to obtain two linearly polarized signal lights that enter the fiber optic sensing ring 5, and then return to the modulator 3 for combining and interference to obtain an interference signal light. Subsequently, the interference signal light is transmitted to the polarization beam splitter assembly 2, and modulation is also implemented on the signal of the peripheral gyro circuit. The main integrated optical device 3 of the Y waveguide is also 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 to 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 the forward input port, the second port and the fourth port are the forward output and reverse input ports, and the third port is the reverse output port;

[0099] The polarization beam splitter assembly used in the technical solution of the present invention, wherein the first port of the polarization beam splitter assembly 2 receives light of any polarization state output by the light source 1, and the second port and the fourth port forwardly output signal light and reference light with equivalent intensities, and after being transmitted and acted on by other optical path devices, return along the original path and reverse input the interference signal light and the matched reference light with equivalent intensities.

[0100] The polarization states of the modulated interference signal light and the matched reference light are orthogonal, and the light intensities are kept consistent, meeting the conditions for canceling and subtracting the relative intensity noise of the same light source. After orthogonal coupling in the polarization beam splitter assembly 2, the intensities are superimposed and output reversely through its third port to reach the detector 6.

[0101] The working wavelength band of the self-amplified spontaneous emission (ASE) light source is 1550 ± 30 nm;

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

[0103] The detector 6 is a photoelectric detector, and its pigtail is preferably a polarization-maintaining fiber, or it can also be a single-mode fiber.

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

[0105] In this embodiment, the input ends of the main Y-waveguide integrated optical device 3 and the slave Y-waveguide integrated optical device 4 can be both fast-axis inputs, that is, the fast axis of the polarization-maintaining fiber is consistent with the TE mode of the integrated Y-waveguide. At this time, the polarization-maintaining pigtail at the input end of the main Y-waveguide integrated optical device 3 and the polarization-maintaining pigtail at the input end of the second port (fast-axis output) of the polarization fraction component 2 are connected at a 0° off-axis angle, and the polarization-maintaining pigtail at the input end of the slave Y-waveguide integrated optical device 4 and the polarization-maintaining pigtail at the input end of the fourth port (slow-axis output) of the polarization beam splitter component 2 are connected at a 90° off-axis angle;

[0106] In the technical solution of the present invention, the optical power splitting ratio of the two output ends of the two proton-exchanged integrated optical Y-waveguide integrated optical devices is 50:50. Output from the same light source, after being modulated by the clockwise and counterclockwise two beams of signal light passing through the main Y-waveguide integrated optical device 3, passes through the fiber optic sensing ring 5 and then returns to the inside of the modulator 3 of the main Y-waveguide integrated optical device for beam combination and interference, forming a modulated interference signal light and transmitting it back to the polarization beam splitter component 2.

[0107] In an embodiment of the present invention, the pigtail of the ASE self-amplified spontaneous emission light source is an ordinary single-mode fiber;

[0108] The pigtails of the polarization beam splitter component 2, the main Y-waveguide integrated optical device 3, the slave Y-waveguide integrated optical device 4, the fiber optic sensing ring 5, and the detector 6 all adopt polarization-maintaining fibers;

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

[0110] In the panda-type fiber, the one horizontally passing through the center of the panda's eyes is the slow axis; the one perpendicular to it passing through the center is the fast axis. Generally, linearly polarized light propagates along the fast axis. When connecting the two ports and rotating by 90°, the light will propagate along the slow axis.

[0111] The main Y waveguide integrated optical device 3 and the slave Y waveguide integrated optical device 4 are proton-exchanged integrated optical Y waveguide integrated optical devices, both of which are single-polarization waveguides with the target output light being linearly polarized light (only capable of transmitting the TE mode), having an extinction ratio greater than 45 dB, and both having fast-axis input;

[0112] Among them, the signal light connecting the second port of the polarization beam splitter assembly 2 to the input end of the main Y waveguide integrated optical device 3 outputs along the fast axis, and the reference light connecting the fourth port of the polarization beam splitter assembly 2 to the input end of the slave Y waveguide integrated optical device 4 outputs along the slow axis;

[0113] Among them, when connecting the polarization-maintaining optical fiber, the fourth port of the polarization beam splitter assembly 2 is connected to the pigtail of the slave Y waveguide integrated optical device 4 at a 90° axis alignment angle, so that the matching reference light changes from the slow axis to transmit along the fast axis;

[0114] The remaining connection points are all connected at a 0° axis alignment angle to ensure that the interference signal light transmits along the fast axis.

[0115] In the technical solution of the present invention, the polarization beam splitter assembly 2 divides the output optical signal of the light source 1 into two beams. One beam is the signal light that transmits through the pigtail of the second port (fast axis of the polarization-maintaining optical fiber), and the other beam is the reference light that transmits through the pigtail of the fourth port (slow axis of the polarization-maintaining optical fiber). The signal light is transmitted through the second port of the polarization beam splitter assembly 2 to the main Y waveguide integrated optical device 3, and the signal light is divided into signal light 1 and signal light 2 through the output end 1 and output end 2 of the main Y waveguide integrated optical device 3. The signal light 1 and signal light 2 respectively enter the fiber optic sensing ring 5, and the signal light 1 and signal light 2 respectively propagate in the fiber optic sensing ring 5 in the counterclockwise and clockwise directions to sense the Sagnac effect; the reference light is transmitted through the fourth port of the polarization beam splitter assembly 2 to the slave Y waveguide integrated optical device 4, and the reference light is divided into reference light 1 and reference light 2 through the output end 1 and output end 2 of the slave Y waveguide integrated optical device 4. The reference light 1 and reference light 2 respectively transmit through the pigtail of the polarization-maintaining optical fiber, and after being butt-jointed at a specific axis alignment angle, the axis alignment angle is determined by the modulation depth parameter applied by the peripheral circuit signal to the main Y waveguide integrated optical device 3. The modulation depth parameter close to π corresponds to a more approximate 90° axis alignment angle, so as to ensure that the interference signal light output after the interference of the signal light 1 and signal light 2 is as equal as possible to the matching reference light that is polarized and output after the combination of the reference light 1 and reference light 2. The interference signal light and the matching reference light are orthogonally coupled and combined in the polarization beam splitter assembly 2; the orthogonally combined optical signal after combination then returns to the detector 6 through the third port of the polarization beam splitter assembly 2, and the optical signal is converted into an electrical signal.

[0116] In the optical path provided by the present invention, a polarization beam splitter assembly 2 is designed, which has two input ports and two output ports. Among them, the first port is the input port, the second port and the fourth port are the forward output ports, and the third port is the reverse output port. The first port receives light with any polarization state emitted by the light source 1, the second port emits and receives the interference signal light passing through the main Y waveguide integrated optical device 3, and the fourth port emits and receives the matching reference light passing through the 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 optical signal output from the polarization beam splitter assembly 2 after coupling and outputs it to the detector 6. Without changing the circuit and algorithm, the relative intensity noise of the light source is suppressed, the optical path loss is reduced, the signal-to-noise ratio of the fiber optic gyroscope is improved, and thus the accuracy of the fiber optic gyroscope is enhanced.

[0117] In the technical solution of the present invention, the polarization directions of the interference signal light and the matching reference light are perpendicular and do not interfere with each other. When they reach the detector, only intensity superposition occurs, thereby suppressing the influence of parasitic coherent effects on the gyroscope accuracy.

[0118] A fiber optic gyroscope optical path design based on a double Y waveguide for suppressing the relative intensity noise of the light source proposed by the present invention. The relative intensity noise of the light source can affect and characterize the output accuracy of the gyroscope through the orthogonal addition compensation effect of the optical fiber. By achieving good suppression of the relative intensity noise of the light source, a high output accuracy of the fiber optic gyroscope can be realized.

[0119] The present invention provides a usage method for a fiber optic gyroscope optical path design based on a double Y waveguide for suppressing the relative intensity noise of the light source, including:

[0120] The light source 1 emits light with any polarization state and transmits it through the first port of the polarization beam splitter assembly 2 into the polarization beam splitter assembly 2, converting the light with any polarization state into two linearly polarized light beams that are orthogonal to each other; the two linearly polarized light beams are respectively output from the polarization beam splitter assembly 2 through the second port and the fourth port of the polarization beam splitter assembly; that is, the polarization beam splitter assembly 2 divides the received linearly polarized signal light into orthogonal signal light and reference light;

[0121] The signal light is transmitted through the second port of the polarization beam splitter assembly 2 into the main Y waveguide integrated optical device 3, where the signal light is polarized, modulated, and split. The split signal light is transmitted into the fiber optic sensing ring 5 for forward and reverse propagation to sense the Sagnac effect. Then, the two signal light beams return to the main Y waveguide integrated optical device 3 again through the fiber optic sensing ring 5 for interference and light combination to obtain the interference signal light, and the interference signal light is transmitted through the second port of the polarization beam splitter assembly 2 into the polarization beam splitter assembly 2;

[0122] The reference light is transmitted through the fourth port of the polarization beam splitter assembly 2 into the integrated optical device 4 of the Y waveguide, where the reference light is polarized and split. The split reference light is partially depolarized through specific off-axis angle connections of two pigtails at the output end, and the partially depolarized reference light returns to the integrated optical device 4 of the Y waveguide again for light combination and re-polarization to obtain a matched reference light. The matched reference light is transmitted through the fourth port of the polarization beam splitter assembly 2 into 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. The two are ideally orthogonal linearly polarized lights, and are orthogonally coupled and combined in the polarization beam splitter assembly 2; in the polarization beam splitter assembly 2, after the interference signal light is coupled with the matched reference light, an orthogonally combined optical signal is transmitted through the third port of the polarization beam splitter assembly 2 to the detector 6.

[0124] The specific steps for obtaining the orthogonally combined optical signal include:

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

[0126] 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, and transmit the signal light 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 output end 1 and output end 2 of the main Y waveguide integrated optical device 3;

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

[0128] ④ After the polarization maintaining pigtail at the fourth port of the polarization beam splitter assembly 2 is subjected to end face beveling or small loop making for high return loss treatment, the optical power intensity of the interference signal light obtained through the pigtail test at the third port of the polarization beam splitter assembly 2 is denoted as I 1 ;

[0129] ⑤ Connect the fourth port of the polarization beam splitter component 2 with the input port of the slave Y-waveguide integrated optical device 4, transmit the reference light to the slave Y-waveguide integrated optical device 4 for polarization, and divide 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; dock the polarization-maintaining optical fiber pigtails of the output end 1 and the output end 2 of the slave Y-waveguide integrated optical device 4 at a specific axis angle, so that the reference light 1 and the reference light 2 are respectively transmitted through the polarization-maintaining optical fiber pigtails of the output port and partially depolarized, and then return to the slave Y-waveguide integrated optical device 4 again, and re-polarize through the slave Y-waveguide integrated optical device 4 to obtain the matching reference light I 2 ;

[0130] ⑥ The interference signal light and the matching reference light are orthogonally coupled and combined in the polarization beam splitter component 2, and the total optical power intensity I of the orthogonal composite optical signal of the interference signal light and the matching reference light obtained by the third port pigtail test of the polarization beam splitter component 2 is 0 , denoted as I 0 , adjust the axis angle of the polarization-maintaining optical fiber at the output end 1 and the output end 2 of the Y-waveguide integrated optical device 4 to be off-axis docked, so that I 1 ≈I 2 , because I 2 =I 0 -I 1 In fact, only the test I 0 , satisfying I 0 ≈2I 1 That's it.

[0131] ⑦ If the previous step is difficult to achieve I 0 ≈2I 1 , then adjust the modulation depth of the modulation signal of the peripheral circuit, and simultaneously measure the total optical power intensity I of the new orthogonal synthesized optical signal 0 ', until I 0 ′=2(I 0 -I 1 );

[0132] ⑧ After any of the above two steps is achieved, the pigtail of the third port of the polarization beam splitter component 2 is connected to the pigtail of the detector 6, so that the orthogonal synthesized optical signal returns to the detector 6 through the third port of the polarization beam splitter component 2, and the optical signal is converted into an electrical signal.

[0133] The off-axis angle described in the present invention is determined by the initial modulation depth of the main Y-waveguide integrated optical device. In the example of the present invention, a larger modulation depth corresponds to an off-axis angle closer to 90° (a higher degree of depolarization) to ensure that the interference signal light output after the interference of signal light 1 and signal light 2 is as equal as possible to the matching reference light output after the synthesis of reference light 1 and reference light 2 and re-polarization.

[0134] The present invention uses two different parameters, namely, the modulation depth parameter of the main Y-waveguide integrated optical device 3 and the off-axis angle of the output pigtail of the slave Y-waveguide integrated optical device 4, for precise control simultaneously, which can ensure that the interference signal light and the matching reference light are orthogonal and have equal optical power.

[0135] For the signal light and the reference light split by the polarization beam splitter assembly of the present invention, differences will occur during the transmission process and they cannot completely remain consistent and orthogonal. The output light intensity error will cause changes in the noise of the interferometric digital closed-loop fiber optic gyroscope composed of the subsequent main Y-waveguide integrated optical device and the fiber optic sensitive ring, further affecting the accuracy of the fiber optic gyroscope. By adjusting the modulation depth parameter of the main Y-waveguide integrated optical device in the fiber optic gyroscope digital closed-loop system, the light intensity difference between the interference signal light and the matching reference light is further compensated, thereby reducing the relative intensity noise of the light source, enabling the fiber optic gyroscope to have a high output signal-to-noise ratio, and thus improving the gyroscope output accuracy; according to the measured output light intensity values of the interference signal light, the orthogonally 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 to achieve precise equal light intensity matching between the matching reference light and the modulated interference signal light.

[0136] The technical solution of the present invention designs a polarization beam splitter assembly, which cooperates with the main and slave Y-waveguides. By using the reference light from the idle fourth port of the polarization beam splitter and through off-axis docking, the polarization degree of the linearly polarized light in the reference light path changes, and under the action of the re-polarization of the slave Y-waveguide, the light intensity ratio is realized, so that the output matching reference light is exactly consistent with the optical power of the modulated interference signal light returned from the main Y-waveguide optical path. At the same time, the index requirements for optical devices are also greatly reduced, which is beneficial to the suppression of light intensity cancellation.

[0137] The technical solution of the present invention uses the orthogonal optical path addition method to suppress the relative intensity noise of the light source at the intrinsic frequency of the fiber optic gyroscope by using the light intensity correlation between the reference light and the signal light emitted from the same light source for noise cancellation. It has good compatibility with the all-digital closed-loop processing technology commonly used in high-precision fiber optic gyroscopes, is highly feasible, does not require additional hardware design of the modulation and demodulation circuit, greatly reduces the index requirements for optical devices, has a relatively simple debugging process, and has a low implementation difficulty.

[0138] Embodiment 1

[0139] Select a self-amplified spontaneous emission light source 1 with a connection wavelength band of 1550 ± 30 nm; the self-amplified spontaneous emission light source emits light with an arbitrary polarization state.

[0140] The first port of the polarization beam splitter assembly 2 is connected to the self-amplified spontaneous emission light source 1 with a connection wavelength band of 1550 ± 30 nm; the polarization beam splitter assembly 2 includes a first port, a second port, a fourth port, and a third port.

[0141] The output port 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, and the output end 1 and the output end 2 of the main Y-waveguide integrated optical device are respectively connected to the optical fiber sensitive ring 5; the fourth port of the polarization beam splitter assembly 2 is connected to 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, the output light of the second port and the fourth port is mutually orthogonal linear polarized light, the second port output is the polarization-maintaining optical fiber fast axis output, and the fourth port output is the polarization-maintaining optical fiber slow axis output.

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

[0143] The polarizer inside the polarization beam splitter assembly 2 is used to convert the received light of any polarization state into linear polarized light; the polarization-maintaining beam splitter inside the polarization beam splitter assembly 2 is used to split the emitted optical signal into mutually orthogonal signal light and reference light; the main Y-waveguide integrated optical device 3 polarizes, splits and modulates the signal light, and the split signal light is transmitted through the optical fiber sensitive ring 5 and then returns to the main Y-waveguide integrated optical device 3 for interference and light combination to obtain the modulated interference signal light; the slave Y-waveguide integrated optical device 4 polarizes and splits the reference light, and the split reference light is depolarized by the off-axis docking part of the polarization-maintaining optical fiber pigtail and then returns to the slave Y-waveguide integrated optical device 4 for re-polarization to obtain the matching reference light; the polarization-maintaining beam splitter inside the polarization beam splitter assembly 2 is used to receive the returned modulated interference signal light and matching reference light, and keep the polarization states orthogonal, and couple to obtain the orthogonal synthesized optical signal; the detector 5 is used to receive the orthogonal synthesized optical signal output by the polarization-maintaining 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 optical fiber sensitive ring 5 of the slave Y-waveguide integrated optical device 4, and the pigtail of the detector 6 all adopt polarization-maintaining optical fibers. Among them, the signal light connected with 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 with 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 optical fiber is connected, the fourth port of the polarization beam splitter assembly 2 and the pigtail of the slave Y-waveguide integrated optical device 4 are connected at a target axis angle of 90°, so that the reference light is transmitted along the fast axis instead of the slow axis; the other connection points are all connected at a target axis angle of 0° to ensure that the interference signal light is transmitted along the fast axis.

[0145] The present invention also provides a method for using a fiber optic gyroscope optical path design based on double Y-waveguides to suppress relative intensity noise of a light source, comprising:

[0146] The light source emits light with an arbitrary polarization state, which is transmitted into the polarizer through the input port of the polarizer, and the light with an arbitrary polarization state is converted into a linearly polarized signal light; the linearly polarized signal light is transmitted into 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 component divides the received linearly polarized signal light into mutually orthogonal signal light and reference light;

[0148] The signal light is transmitted into the main Y-waveguide integrated optical device through port 2 of the polarization-maintaining beam splitter, where signal light polarization, modulation, and beam splitting are performed. The split signal light is transmitted into the fiber optic sensing ring for transmission and sensitivity to the Sagnac effect. The signal light traveling clockwise and counterclockwise returns to the main Y-waveguide integrated optical device 4 for polarization, beam combination, and interference again, obtaining an interference signal light. The interference signal light is transmitted back to the polarization-maintaining beam splitter through port 2 of the polarization-maintaining beam splitter along the original path;

[0149] The reference light is transmitted into the slave Y-waveguide integrated optical device through port 4 of the polarization-maintaining beam splitter, where reference light polarization and beam splitting are performed. The split reference light is partially depolarized through specific polarization axis angles of two polarization-maintaining fiber pigtails at output port 1 and output port 2, and the partially depolarized reference light returns to the slave Y-waveguide integrated optical device along the original path for beam combination and re-polarization, obtaining a matching reference light. The matching reference light is transmitted into 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 component, and the matching reference light is reversely input from port 4 of the polarization-maintaining beam splitter component. The two are ideally orthogonally polarized linearly polarized lights, which are orthogonally coupled and combined in the polarization-maintaining beam splitter to form an orthogonally combined optical signal, and 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 component 3, and the reference light is reversely input from the fourth port of the polarization beam splitter component 3. The two are ideally orthogonally polarized linearly polarized lights, which are orthogonally coupled and combined inside the polarization beam splitter component 3 to form an orthogonally combined optical signal, and finally are transmitted to the detector 6 through the third port of the polarization beam splitter component 3.

[0152] The technical solution example of the present invention uses two Y-waveguide integrated optical devices, and a polarization beam splitter component composed of 1 polarizer and one polarization-maintaining beam splitter, so that the polarization states of the output interference signal light and the matching reference light are orthogonal, and the intensities reaching the detector are kept consistent, meeting the condition of cancellation by orthogonal addition of the coherence intensity noise of the light source.

[0153] In the example of the technical solution of the present invention, the polarization beam splitter component 2 is used. The optical power splitting ratios of the light output from the two output ends to the main Y waveguide integrated optical device and the slave Y waveguide integrated optical device are 1:1, and the polarization states are orthogonal. The two signal light beams output from the main Y waveguide integrated optical device respectively pass through the optical fiber sensing ring in the clockwise and counterclockwise directions and then return to the inside of the modulator for beam combination and interference, and the formed interference signal light is transmitted back to the polarization beam splitter component. The two reference light beams output from the slave Y waveguide integrated optical device are connected off-axis through polarization-maintaining optical fibers and then return to the modulator to be re-polarized. The formed matching reference light is transmitted back to the polarization beam splitter component, and orthogonally coupled with the interference signal light of the same origin inside the polarization beam splitter, with intensity superposition and noise cancellation.

[0154] As mentioned above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

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

2. The fiber optic gyroscope according to claim 1, characterized in that: The main Y-waveguide integrated optical device (3) and the slave Y-waveguide integrated optical device (4) can only transmit one transmission mode, wherein the main Y-waveguide integrated optical device (3) plays the role of polarization, splitting and modulation, and the Y-waveguide integrated optical device (4) plays the role of polarization and splitting; the optical power target splitting ratio of the output port 1 and the output port 2 of the main Y-waveguide integrated optical device (3) and the slave Y-waveguide integrated optical device (4) are both 50:50, the chip polarization extinction ratio is ≥40dB, the pigtail polarization crosstalk is ≤-20dB; and the back light reflection is ≤-45dB.

3. The fiber optic gyroscope according to claim 1, characterized in that: The polarization beam splitter component (2), the main Y-waveguide integrated optical device (3), the slave Y-waveguide integrated optical device (4) and the optical fiber sensitive ring (5) are all connected by polarization-maintaining optical fiber; the light source (1) and the polarization beam splitter component (2) are connected by ordinary single-mode optical fiber, or by polarization-maintaining optical fiber; the detector (6) and the polarization beam splitter component (2) are connected 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 wavelength bands of the light source (1), polarization beam splitter assembly (2), main Y-waveguide integrated optical device (3), slave Y-waveguide integrated optical device (4), optical fiber sensitive ring (5) and detector (6) are 850 nm, 1310 nm, 1550 nm, 1550±30 nm, 1310±30 nm or 850±30 nm.

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

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

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

8. The fiber optic gyroscope according to claim 1, characterized in that: The light source (1) emits light in an arbitrary polarization state and transmits it to the polarization beam splitter component (2) through the first port of the polarization beam splitter component (2). In the polarization beam splitter component (2), the light in an arbitrary polarization state is converted into linear polarization light; the polarization beam splitter component (2) splits the received light in an arbitrary polarization state into reference light and signal light that are orthogonal to each other; the signal light is transmitted to the main Y-waveguide integrated optical device (3) through the second port of the polarization beam splitter component (2) to polarize, split and modulate the signal light, and the split signal light is transmitted to the optical fiber sensitive ring (5) to sense the Sagnac effect. The signal light containing sensitive information is returned to the main Y-waveguide integrated optical device (3) through the optical fiber sensitive ring (5) to perform light combination interference to obtain 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 route of the pigtail at the second port of the polarization beam splitter component (2) from the fast axis to the polarization beam splitter component (2); the reference light is transmitted to the main Y-waveguide integrated optical device (3) through the second port of the polarization beam splitter component (2). The reference light is transmitted to the Y-waveguide integrated optical device (4) through the fourth port pigtail of the polarization beam splitter component (2) to perform reference light polarization and beam splitting. After the reference light is partially depolarized, it is returned to the Y-waveguide integrated optical device (4) for re-polarization to match the interference signal light to obtain a matching reference light. The matching reference light is transmitted along the fast axis of the polarization-maintaining optical fiber through the pigtail of the input port of the Y-waveguide integrated optical device (2), and then deflected by 90° along the pigtail of the fourth port of the polarization beam splitter component (2) and then returned from the slow axis to the polarization beam splitter component (2). The matching reference light entering along the slow axis through the fourth port of the polarization beam splitter component (2) is orthogonally coupled with the interference signal light entering along the fast axis through the second port to obtain a synthesized light signal. The synthesized light signal is transmitted to the detector (6) through the third port of the polarization beam splitter component (2) and converted into an electrical signal, which is then processed by a subsequent gyro circuit.

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

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