Fiber-optic gyroscope engine based on silicon-based film lithium niobate

Abstract

The invention relates to a fiber-optic gyroscope engine based on silicon-based film lithium niobate. The engine comprises a light source, a polarizer, a coupler, a beam splitter, a modulator and a light detector which are sequentially integrated through a thin film lithium niobate waveguide, the waveguide comprises a lithium niobate layer, a silicon dioxide layer and a silicon layer which are sequentially distributed in a stacked mode from top to bottom, and the polarizer comprises an input arc waveguide, a semicircular waveguide and an output arc waveguide. The input arc-shaped waveguide and the output arc-shaped waveguide are both in a 4 / 1 arc shape with a certain radius, the semicircular waveguide is in a semicircular arc shape with a certain radius, the arc center of the input arc-shaped waveguide, the arc center of the semicircular waveguide and the arc center of the output arc-shaped waveguide are collinearly distributed in the extending direction of the polarizer, and the certain radius is larger than 50 microns. Compared with a traditional polarizer structure, such as an S-shaped structure, the polarizer has the advantages that the optical signal transmission loss is remarkably reduced, the waveguide process tolerance is improved, and the overall performance of a fiber-optic gyroscope engine, especially in high-precision application, is favorably improved.

Description

Technical Field

[0001] The invention belongs to the field of optical engines, and in particular relates to an optical fiber gyroscope engine based on silicon-based thin film lithium niobate. Background Art

[0002] As a high-precision navigation and positioning device, the core of the lithium niobate fiber gyroscope is to use the electro-optical effect of lithium niobate crystals to realize the modulation and detection of optical signals, thereby accurately measuring the rotation rate. It is widely used in aerospace, automotive navigation, ship navigation, robotics and other fields.

[0003] As one of the key components of lithium niobate fiber gyroscope, polarizer is responsible for generating and maintaining the polarization state of light, and its performance directly affects the sensitivity, stability and measurement accuracy of the gyroscope. However, the traditional polarizer structure often adopts a linear structure or a simple curved structure, which has high light loss and is prone to light scattering and reflection at sharp bends, resulting in a decrease in signal strength and affecting measurement accuracy. Summary of the invention

[0004] Based on this, it is necessary to address the above-mentioned technical problems. The purpose of this application is to provide a fiber optic gyroscope engine based on silicon-based thin film lithium niobate to reduce the optical loss in the signal transmission process, thereby improving the optical signal strength of the fiber optic gyroscope engine and improving the measurement accuracy of the fiber optic gyroscope engine.

[0005] The purpose of this application is achieved by the following technical solutions:

[0006] An optical fiber gyroscope engine based on silicon-based thin film lithium niobate, comprising:

[0007] A light source, a polarizer, a coupler, a beam splitter, a modulator and a light detector are integrated and arranged in sequence via a thin-film lithium niobate waveguide, wherein the thin-film lithium niobate waveguide comprises a lithium niobate layer, a silicon dioxide layer and a silicon layer which are stacked and distributed in sequence from top to bottom;

[0008] The polarizer includes an input arc waveguide, a semicircular waveguide and an output arc waveguide which are arranged in sequence. The input arc waveguide and the output arc waveguide are both in the shape of a 4 / 1 arc with a certain radius. The semicircular waveguide is in the shape of a semicircular arc with a certain radius. The arc centers of the input arc waveguide, the semicircular waveguide and the output arc waveguide are collinearly distributed along the extension direction of the polarizer, and the certain radius is greater than 50um.

[0009] Further, the coupler is 2×2MM I;

[0010] The coupler 3 is provided with an input end, a coupling end and an output end, the input end is cascaded with the polarizer, the coupling end is cascaded with the photodetector, and the output end is cascaded with the beam splitter;

[0011] The widths of the transition waveguides at the input end, the coupling end and the output end are all greater than 0.8um; and the spacing between the input end and the coupling end is greater than 2um.

[0012] Further, the beam splitter is a 1×2MM I or Y-type beam splitter, and the splitting ratio of the beam splitter is 1:1;

[0013] The beam splitter is provided with a signal input end, a first light beam output end, and a second light beam output end, the signal input end is cascaded with the output end of the coupler; the first light beam output end and the second light beam output end are cascaded with the modulator respectively;

[0014] The distance between the first light beam output end and the second light beam output end is greater than 2 um.

[0015] Furthermore, the modulator includes a plurality of signal electrodes, a plurality of ground electrodes and a plurality of modulation arms; the signal electrodes and the ground electrodes are both in the shape of parallel plates.

[0016] Two signal electrodes are arranged between the two modulation arms. The two signal electrodes are arranged opposite to each other along the radial direction of the two modulation arms, respectively taking the two modulation arms as the center. A ground electrode is arranged on one side of the modulation arms relative to the signal electrode.

[0017] The distance between the two signal electrodes is greater than 20um.

[0018] Furthermore, the lithium niobate layer is also provided with a spot converter. When the spot converter is in operation, the light source of the fiber optic gyroscope engine is coupled and matched with the polarizer through the spot converter; or, the output beam of the modulator is coupled and output through the spot converter.

[0019] Furthermore, the spot converter includes an inverse-tapered lithium niobate waveguide layer and a silicon dioxide cladding layer covering the inverse-tapered lithium niobate waveguide layer.

[0020] Furthermore, the photodetector is coupled to the coupling end of the coupler through a spot converter, and the photodetector is a PIN photodiode or an avalanche photodiode.

[0021] Furthermore, the light source is a broadband light source with an input power greater than 10 mW and a spectral bandwidth greater than 40 nm, and the light source and the light detector are arranged on the same side of the thin film lithium niobate waveguide.

[0022] Furthermore, the lithium niobate layer includes a first core layer and a second core layer, the first core layer is stacked on the second core layer, and the cross-sectional outer contour of the first core layer perpendicular to the extension trajectory of the lithium niobate layer is a trapezoid, the bottom side of the trapezoid is closer to the second core layer than the top side of the trapezoid, and the angle between any hypotenuse of the trapezoid and the bottom side is greater than 60°.

[0023] Furthermore, the fiber optic gyroscope engine is also provided with a fiber optic ring. When the fiber optic gyroscope engine is in a rotating state, the first modulated light beam and the second modulated light beam output by the modulator are transmitted in relative directions through the fiber optic ring respectively, and the first modulated light beam and the second modulated light beam output by the modulator generate a phase difference at the junction of the fiber optic ring.

[0024] In the above technical scheme, the present application adopts the polarizer structure design of input arc waveguide, semicircular waveguide and output arc waveguide, and the arc centers of the input arc waveguide, semicircular waveguide and output arc waveguide are collinearly distributed along the extension direction of the polarizer, and their radii are all greater than 50um. The design of the input arc waveguide allows light to enter smoothly, reducing mode mismatch and reflection loss. The design of the semicircular waveguide improves the selectivity for different polarization states, effectively modulates the polarization state of the optical signal, thereby enhancing the sensitivity of the system. Finally, the output arc waveguide can efficiently convert the modulated optical signal into the required TE mode, thereby achieving accurate optical signal output. Compared with the traditional polarizer straight line or simple curved structure (such as S-shaped structure), the design of the polarizer significantly improves the transmission efficiency and polarization selectivity of the optical signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic structural diagram of a fiber optic gyroscope engine based on silicon-based thin film lithium niobate in the present invention;

[0027] Figure 2 This is a schematic diagram of a thin-film lithium niobate waveguide structure in one embodiment of the present invention;

[0028] Figure 3 A schematic diagram of the structure of a polarizer in one embodiment of the present invention;

[0029] Figure 4 This is the result of the simulation experiment of the traditional polarizer S-type structure;

[0030] Figure 5 This is a diagram showing the results of a simulation experiment of a polarizer in one embodiment of the present invention;

[0031] Figure 6 A schematic diagram of the structure of a coupler in one embodiment of the present invention;

[0032] Figure 7 Schematic diagram of the structure of a beam splitter in one embodiment of the present invention.

[0033] In the figure:

[0034] 1. Light source; 2. Polarizer; 21. Input arc waveguide; 22. Semicircular waveguide; 23. Output arc waveguide; 3. Coupler; 31. Input end; 32. Coupling end; 33. Output end; 4. Beam splitter; 41. Signal input end; 42. First light beam output end; 43. Second light beam output end; 5. Modulator; 6. Photodetector; 7. Thin film lithium niobate waveguide; 71. Lithium niobate layer; 711. First core layer; 712. Second core layer; 72. Silicon dioxide layer; 73. Silicon layer. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element, or there may be an element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element, or there may be an element centered thereon. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0037] Unless otherwise defined, all technical terms and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the invention in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items.

[0038] like Figure 1 As shown, in one of the embodiments, a fiber optic gyroscope engine based on silicon-based thin film lithium niobate is disclosed, and the fiber optic gyroscope engine includes a light source 1, a polarizer 2, a coupler 3, a beam splitter 4, a modulator 5 and a light detector 6 which are integrated in sequence via a thin film lithium niobate waveguide 7.

[0039] Specifically, Figure 2As shown, the thin-film lithium niobate waveguide 7 includes a lithium niobate layer 71, a silicon dioxide layer 72, and a silicon layer 73 stacked in sequence from top to bottom. The lithium niobate layer 71 can modulate and propagate optical signals by utilizing its linear electro-optical effect. The silicon dioxide layer 72 plays the role of isolation and protection, reduces the loss of optical signals during propagation, and provides appropriate refractive index matching to ensure efficient transmission of optical signals. The silicon layer 73 provides solid mechanical support and can effectively dissipate heat to keep the temperature of the waveguide stable during operation, thereby ensuring the transmission efficiency of optical signals and the overall performance of the system.

[0040] Schematically, the thin-film lithium niobate waveguide 7 presents a ridge waveguide structure, which can be prepared by an etching process such as Ar ion dry etching. In the lithium niobate layer 71, a first core layer 711 and a second core layer 712 made of lithium niobate material are overlapped, wherein the first core layer 711 is stacked on the second core layer 712, and the cross-sectional outer contour of the first core layer 711 perpendicular to the extension track of the lithium niobate layer 71 is a trapezoid, the bottom side of the trapezoid is closer to the second core layer 712 than the top side of the trapezoid, and the angle between any hypotenuse of the trapezoid and the bottom side is greater than 60°. Compared with the traditional planar waveguide, this structural design can effectively constrain the light beam, so that the propagation of the optical signal inside the waveguide is more concentrated, thereby reducing the signal attenuation caused by scattering and reflection, helping to improve the propagation efficiency of the optical signal and optimize the optical performance of the waveguide.

[0041] Schematically, the light source 1 is used to generate a stable laser beam. The light source is a broadband light source 1 with an input power greater than 10 mW and a spectral bandwidth greater than 40 nm. Semiconductor lasers or superluminescent diodes can usually be selected as implementation solutions. These devices have excellent frequency stability and low noise characteristics, ensuring the accuracy of the measurement. In addition, the light source 1 and the light detector 6 are both arranged on the same side of the thin-film lithium niobate waveguide 7. This compact design makes the overall volume of the engine smaller, thereby improving the integration.

[0042] like Figure 3 As shown, the polarizer 2 is composed of an input arc waveguide 21, a semicircular waveguide 22 and an output arc waveguide 23 connected in sequence. The input arc waveguide 21 and the output arc waveguide 23 are both in the shape of a 1 / 4 arc with a certain radius, while the semicircular waveguide 22 is in the shape of a semicircle with a certain radius. The arc centers of the input arc waveguide 21, the semicircular waveguide 22 and the output arc waveguide 23 are collinear along the extension direction of the polarizer 2, and the radii of the certain radius are all greater than 50μm. Its input mode is a TE mixed TM mode, and the output mode is TE, which ensures that the light beam output by the polarizer 2 has a consistent polarization state, effectively filters out polarized light, and improves the accuracy and stability of the measurement.

[0043] Through this structural design, the polarizer 2 can effectively guide the optical signal and optimize the polarization control. Further, the simulation experiment is carried out by Lumer ica l FDTD software, such as Figure 4 , Figure 5 As shown, Figure 4 This is the simulation result of the traditional polarizer S-type structure. Figure 5 is the simulation result of the polarizer 2 structure in this embodiment, wherein, transmission (dB) is the transmission loss during the transmission of the optical signal, in dB; Δw is the error between the actual value and the design value of the length of the trapezoidal bottom side of the cross section of the second core layer in the polarizer in industrial manufacturing, in nm. The simulation results show that under the same conditions, compared with the traditional polarizer S-type structure, within the process tolerance ±200nm, the polarizer 2 structure in this embodiment has a higher extinction ratio, which can ensure that its extinction ratio>20dB and loss<1dB, indicating that the stronger the transmission capacity of the output specific polarized light, i.e., TE mode light, the stronger the polarization selectivity, effectively suppresses the interference of noise and non-polarized light, ensures that the quality of the transmission signal is higher, improves its waveguide process tolerance, and shows better performance and reliability. It is worth noting that the compact design of the fiber optic gyro engine enables its size to reach 7mmx1.5mm, which provides more possibilities for high-precision applications. This size advantage not only optimizes space utilization, but also promotes a wider range of application prospects.

[0044] like Figure 6 As shown, the coupler 3 is a 2×2 MMI, including an input end 31, a coupling end 32 and an output end 33. The input end 31 is cascaded with the polarizer 2, the coupling end 32 is cascaded with the photodetector 6, and the output end 33 is cascaded with the beam splitter 4. The transition waveguide widths of the input end 31, the coupling end 32 and the output end 33 are all greater than 0.8um, which can effectively reduce the transmission loss of the optical signal during the input, coupling and output processes, reduce the mutual interference between different modes, ensure the stability and clarity of the signal, and improve the mode matching efficiency. At the same time, the increase in the width of the transition waveguide helps to disperse the heat more evenly, reduce the performance degradation caused by local overheating, thereby enhancing the thermal stability and reliability of the equipment, especially in a high-power working environment. The spacing between the input end 31 and the coupling end 32 is greater than 2um, which further avoids mutual interference and crosstalk between optical signals, ensures the independent transmission of signals, and also enables the output light beam of the coupling end 32 to be better aligned with the coupling structure, thereby enhancing the coupling efficiency of the optical signal. At the same time, a larger spacing and waveguide width can increase the tolerance of industrial manufacturing and reduce the impact of errors in the production process.

[0045] The beam splitter 4 may be a 1×2 MMI or Y-type beam splitter 4, and the beam splitter 4 has a splitting ratio of 1:1. Figure 7As shown, the beam splitter 4 is a 1×2 MMI, provided with a signal input end 41, a first beam output end 42 and a second beam output end 43. The signal input end 41 is cascaded with the output end 33 of the coupler 3, and the first beam output end 42 and the second beam output end 43 are cascaded with the modulator 5 respectively. The output beam of the coupler 3 is received through the signal input end 41, and is divided into two beams with equal optical power, which are outputted by the first beam output end 42 and the second beam output end 43 respectively. Among them, the spacing between the first beam output end 42 and the second beam output end 43 is greater than 2um, which helps to reduce the mutual interference and crosstalk between the output beams and ensure the signal stability of each output channel. The tapered waveguide width of the first beam output end 42 and the second beam output end 43 is greater than 0.8um, which helps to effectively guide the beam, reduce the light loss caused by waveguide mismatch or reflection, ensure the transmission efficiency of the optical signal, and also improve the coupling efficiency of the optical signal with the subsequent modulator 5, ensuring that a larger proportion of the optical power can be effectively absorbed and used by the modulator 5. Through the design of the coupler 3 and the beam splitter 4, the reciprocity of the optical path is met, the extra phase difference is eliminated, and the light beam output by the polarizer 2 is split into two light beams with equal optical power.

[0046] The modulator 5 includes a plurality of signal electrodes, a plurality of ground electrodes and a plurality of modulation arms, and the signal electrodes and the ground electrodes are parallel plate-shaped and are metal electrodes. The signal electrodes and the ground electrodes can be planar electrodes, which are arranged on the lithium niobate layer 71 to generate a uniform electric field and improve the modulation accuracy. Specifically, two signal electrodes are arranged between the two modulation arms, and the two signal electrodes are arranged relative to each other along the radial direction of the two modulation arms, and the spacing between the two signal electrodes is greater than 20um, so as to further reduce the interference between different signals, improve the modulation efficiency, and also help to improve the thermal stability and avoid the heat accumulation generated under high-power working conditions. With the two modulation arms as the center, the modulation arms are respectively provided with ground electrodes on one side relative to the signal electrode, and the spacing between adjacent signal electrodes and ground electrodes is greater than 3um, thereby providing different modulation paths for the two optical signals received by the modulator 5, and independent modulation can be performed. By applying modulation signals of different amplitudes or amplitudes respectively, it is beneficial to compensate for the non-reciprocal phase difference caused by process errors, and further improves the modulation symmetry, reduces the nonlinear phase error caused by modulation asymmetry, and helps to improve the measurement accuracy of the fiber optic gyroscope engine. At the same time, the spacing design between adjacent electrodes can effectively reduce the electric field interference between adjacent electrodes, ensuring that the modulation signal output by the signal electrode can remain clear and stable, thereby improving the modulation accuracy and efficiency.

[0047] Furthermore, the lithium niobate layer 71 is also provided with a spot mode converter, which can be arranged between the light source 1 and the polarizer 2, or between the modulator 5 and the optical detector 6. Then, when the spot mode converter is in working state, the light source 1 of the fiber optic gyro engine can be coupled and matched with the polarizer 2 through the spot mode converter, and the mode of the light source 1 can be effectively adjusted to ensure the best coupling efficiency and minimize light loss and reflection; or, the output light beam of the modulator 5 can be coupled and output through the spot mode converter, and the modulated light signal can be converted into a mode suitable for receiving by the optical detector 6, thereby improving the sensitivity and accuracy of the signal.

[0048] Specifically, the mode spot converter includes an inverted tapered lithium niobate waveguide layer and a silicon dioxide cladding covering the inverted tapered lithium niobate waveguide layer. The silicon dioxide cladding is made of silicon dioxide material and has excellent optical properties and low loss characteristics. Through this structural design, light guidance can be effectively achieved, and combined with the structure of the inverted tapered lithium niobate waveguide layer, mode conversion can be achieved. The inverted tapered design of the inverted tapered lithium niobate waveguide layer helps to gradually increase the cross-section of the light beam, thereby improving the efficiency of mode conversion, so that the input light beam can be smoothly adapted to the downstream optical elements, such as the polarizer 2 or the modulator 5, etc., reducing the distortion of the optical signal during transmission, thereby improving the signal quality and measurement accuracy.

[0049] Preferably, a spot converter is provided between the photodetector 6 and the coupler 3, so that the photodetector 6 is coupled with the coupling end 32 of the coupler 3 through the spot converter, and the output light beam from the coupler 3 can be effectively adjusted to a mode suitable for reception by the photodetector 6, so that the photodetector 6 can capture the signal more effectively, and the detection accuracy and sensitivity are improved, especially in low light intensity environments. The photodetector 6 can be a PIN photodiode or an avalanche photodiode. The PIN photodiode has a faster response time and a lower dark current, so that in a high-speed rotating fiber optic gyroscope engine, even in a rapidly changing light signal environment, the accurate reception and processing of the signal can be ensured. On the other hand, the avalanche photodiode utilizes the photomultiplier effect and can show excellent high-sensitivity detection capabilities under extremely low light intensity conditions, so it is suitable for those application scenarios in the fiber optic gyroscope engine that require high gain and high-precision measurement. In low light intensity environments, such as deep sea exploration or long-distance communication, the avalanche photodiode can ensure the accurate capture of weak light signals, further improving the measurement accuracy and stability of the fiber optic gyroscope engine.

[0050] In an optional embodiment, the fiber optic gyroscope engine is further provided with a fiber optic ring. When the fiber optic gyroscope engine is in a rotating state, the first modulated light beam and the second modulated light beam output by the modulator 5 are transmitted in relative directions through the fiber optic ring, and the first modulated light beam and the second modulated light beam output by the modulator 5 generate a phase difference at the junction of the fiber optic ring. Schematically, the first modulated light beam is transmitted clockwise in the fiber optic ring, and the second modulated light beam is transmitted counterclockwise in the fiber optic ring. Since the propagation speed of light remains unchanged, the rotation of the fiber optic gyroscope engine causes the phase difference between the first modulated light beam and the second modulated light beam in the fiber optic ring to change continuously. Due to the interference effect, when the two beams of light meet at the junction, their interference pattern will change with the change of the phase difference. After passing through the modulator 5, the beam splitter 4 and the coupler 3 in turn, the two beams of light are combined and output to the optical detector 6, so that the changes in the interference pattern can be analyzed in real time and converted into accurate angular velocity information. This process provides the fiber optic gyroscope engine with high-precision rotation detection capability, which is widely used in navigation and positioning systems.

[0051] The above-mentioned embodiments only express several implementation methods of the embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the embodiments of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the embodiments of the present application, and these all belong to the protection scope of the embodiments of the present application.

Claims

1. A fiber optic gyroscope engine based on silicon-based thin film lithium niobate, comprising: A light source (1), a polarizer (2), a coupler (3), a beam splitter (4), a modulator (5) and a light detector (6) are integrated and arranged in sequence via a thin-film lithium niobate waveguide (7), wherein the thin-film lithium niobate waveguide (7) comprises a lithium niobate layer (71), a silicon dioxide layer (72) and a silicon layer (73) which are stacked and arranged in sequence from top to bottom, and wherein the polarizer (2) comprises an input arc waveguide (21), a semicircular waveguide (22 ) and an output curved waveguide (23), the input curved waveguide (21) and the output curved waveguide (23) are both in the shape of a 4 / 1 arc with a certain radius, the semicircular waveguide (22) is in the shape of a semicircular arc with a certain radius, the arc center of the input curved waveguide (21), the arc center of the semicircular waveguide (22) and the arc center of the output curved waveguide (23) are colinearly distributed along the extension direction of the polarizer (2), and the certain radius is greater than 50um.

2. The fiber optic gyro engine according to claim 1, characterized in that: The coupler (3) is a 2×2 MMI; The coupler (3) is provided with an input end (31), a coupling end (32) and an output end (33); the input end (31) is cascade-connected with the polarizer (2); the coupling end (32) is cascade-connected with the photodetector (6); and the output end (33) is cascade-connected with the beam splitter (4); The transition waveguide widths of the input end (31), the coupling end (32) and the output end (33) are all greater than 0.8 um; and the spacing between the input end (31) and the coupling end (32) is greater than 2 um.

3. The fiber optic gyro engine according to claim 2, characterized in that: The beam splitter (4) is a 1×2 MMI or Y-type beam splitter, and the beam splitting ratio of the beam splitter (4) is 1:1; The beam splitter (4) is provided with a signal input end (41), a first light beam output end (42) and a second light beam output end (43); the signal input end (41) is cascade-connected with the output end (33) of the coupler (3); the first light beam output end (42) and the second light beam output end (43) are cascade-connected with the modulator (5) respectively; The distance between the first light beam output end (42) and the second light beam output end (43) is greater than 2 um.

4. The fiber optic gyro engine according to claim 1, characterized in that: The modulator (5) comprises a plurality of signal electrodes, a plurality of ground electrodes and a plurality of modulation arms; the signal electrodes and the ground electrodes are both in the shape of parallel plates; Two signal electrodes are arranged between the two modulation arms, and the two signal electrodes are arranged opposite to each other along the radial direction of the two modulation arms, respectively taking the two modulation arms as the center, and the modulation arms are provided with the ground electrode on one side relative to the signal electrode; The distance between the two signal electrodes is greater than 20 um.

5. The fiber optic gyro engine according to claim 1, characterized in that: The lithium niobate layer (71) is also provided with a spot mode converter. When the spot mode converter is in operation, the light source (1) of the fiber optic gyroscope engine is coupled and matched with the polarizer (2) through the spot mode converter; or, the output light beam of the modulator (5) is coupled and output through the spot mode converter.

6. The fiber optic gyro engine according to claim 5, characterized in that: The spot converter comprises an inverse-tapered lithium niobate waveguide layer and a silicon dioxide cladding layer covering the inverse-tapered lithium niobate waveguide layer.

7. The fiber optic gyro engine according to claim 1, characterized in that: The light detector (6) is coupled to the coupling end (32) of the coupler (3) via a spot converter, and the light detector (6) is a PIN photodiode or an avalanche photodiode.

8. The fiber optic gyro engine according to claim 1, characterized in that: The light source (1) is a broadband light source (1) with an input power greater than 10 mW and a spectral bandwidth greater than 40 nm. The light source (1) and the light detector (6) are arranged on the same side of the thin-film lithium niobate waveguide (7).

9. The fiber optic gyro engine according to claim 1, characterized in that: The lithium niobate layer (71) comprises a first core layer (711) and a second core layer (712), wherein the first core layer (711) is stacked on the second core layer (712), and the outer contour of the cross section of the first core layer (711) perpendicular to the extension track of the lithium niobate layer (71) is a trapezoid, wherein the bottom side of the trapezoid is closer to the second core layer (712) than the top side of the trapezoid, and the angle between any hypotenuse of the trapezoid and the bottom side is greater than 60°.

10. The fiber optic gyro engine according to claim 1, characterized in that: The fiber optic gyroscope engine is also provided with a fiber optic ring. When the fiber optic gyroscope engine is in a rotating state, the first modulated light beam and the second modulated light beam output by the modulator (5) are transmitted in opposite directions respectively through the fiber optic ring. The first modulated light beam and the second modulated light beam output by the modulator (5) generate a phase difference at the junction of the fiber optic ring.

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