Fiber-optic gyroscope chip and system

Abstract

The invention provides a fiber-optic gyroscope chip and a fiber-optic gyroscope system. The fiber-optic gyroscope chip comprises an integrated optical waveguide structure located on a thin-film lithium niobate layer; the integrated optical waveguide structure comprises a plurality of sections of photoelectric modulation structures, the plurality of sections of photoelectric modulation structures are located in the cladding on the thin-film lithium niobate layer, the plurality of sections of photoelectric modulation structures are sequentially arranged in the light propagation direction on the fiber-optic gyroscope chip, and each section of photoelectric modulation structure comprises electrodes arranged on the two sides of the integrated optical waveguide structure; each section of photoelectric modulation structure is configured to be switched on or switched off under the driving of a control circuit of the fiber-optic gyroscope system to obtain a plurality of modulation structures with different effective electrode lengths and a modulation mode corresponding to each modulation structure so as to realize multi-gear reconfigurable switching of the phase modulation sensitivity and the linear range of the fiber-optic gyroscope.

Description

Technical Field

[0001] This application relates to the field of optical device technology, and in particular to a fiber optic gyroscope chip and system. Background Technology

[0002] A fiber optic gyroscope is an angular velocity measurement device based on the Sagnac effect, widely used in inertial navigation systems. It offers advantages such as no moving parts, high reliability, and a wide measurement range, making it suitable for various platforms including aircraft, ships, and missiles. A fiber optic gyroscope typically consists of a discrete light source, a polarization-maintaining fiber optic loop, an electro-optic modulator, and a photodetector, and outputs angular velocity through closed-loop demodulation.

[0003] To improve dynamic range and sensitivity, related technologies often employ multiple fiber optic gyroscopes or switch ranges electronically within a single system. However, the former is structurally complex and bulky, while the latter is limited by a fixed electrode structure, making it difficult to effectively avoid modulation saturation and nonlinear errors. With the development of integrated optical platforms, integrating key optical paths into thin-film lithium niobate chips has become a trend. However, current integration solutions mostly use fixed-length electro-optic modulators, which cannot flexibly adjust modulation characteristics, making it difficult for the system to simultaneously meet the requirements of high precision and large dynamic range.

[0004] Therefore, there is an urgent need for a fiber optic gyroscope chip that can achieve multiple sensitivity and range switching on the same chip to overcome the problems of complex structure and limited modulation performance in related technologies. Summary of the Invention

[0005] This application provides a fiber optic gyroscope chip and system capable of forming modulation modes with different effective electrode lengths. It achieves multi-level switching of phase modulation sensitivity and linear range. The technical solution of this application is implemented as follows: This application provides a fiber optic gyroscope chip for use in a fiber optic gyroscope system; the fiber optic gyroscope chip includes: Integrated optical waveguide structure located in a thin-film lithium niobate layer; A multi-segment optoelectronic modulation structure is located in the cladding layer on a thin-film lithium niobate layer. The multi-segment optoelectronic modulation structure is arranged sequentially along the light propagation direction on the fiber optic gyroscope chip. Each optoelectronic modulation structure includes electrodes disposed on both sides of the integrated optical waveguide structure. Each photoelectric modulation structure is configured to be turned on or off under the drive of the fiber optic gyroscope system's control circuit, resulting in multiple modulation structures with different effective electrode lengths and corresponding modulation modes for each structure. This enables multi-level reconfigurable switching of the fiber optic gyroscope's phase modulation sensitivity and linear range. In some embodiments, the integrated optical waveguide structure includes an optical waveguide core region, which is an asymmetric double-ridge waveguide; each optoelectronic modulation structure includes at least one of a first modulation signal electrode connected to a first signal electrode and a second modulation signal electrode connected to a second signal electrode, and at least one modulation ground electrode connected to a common ground electrode; one of the first modulation signal electrode and the second modulation signal electrode, and a modulation ground electrode are disposed on both sides of each optical waveguide core region; the common ground electrode, the first signal electrode, and the second signal electrode are electrically connected to a control circuit, and the first signal electrode and the second signal electrode are configured to be turned on or off under the drive of the control circuit.

[0006] In some embodiments, the multi-segment optoelectronic modulation structure includes at least a first modulation segment, a second modulation segment, and a third modulation segment; the modulation modes include at least a first mode, a second mode, and a third mode; the first modulation segment includes at least one first modulation signal electrode and at least one modulation ground electrode; the second modulation segment includes at least one second modulation signal electrode and at least one modulation ground electrode; the third modulation segment includes at least one second modulation signal electrode and at least one modulation ground electrode; when the first signal electrode is on and the second signal electrode is off, the first modulation segment is in a modulation working state, and the multi-segment optoelectronic modulation structure is in the first mode; when the first signal electrode is off and the second signal electrode is on, the second and third modulation segments are in a modulation working state, and the multi-segment optoelectronic modulation structure is in the second mode; when both the first and second signal electrodes are on, the first, second, and third modulation segments are all in a modulation working state, and the multi-segment optoelectronic modulation structure is in the third mode.

[0007] In some embodiments, the first modulation segment has a first length, which is the sum of the electrode lengths in the first modulation segment where the first modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region in the optical propagation direction; the second modulation segment has a second length, which is the sum of the electrode lengths in the second modulation segment where the second modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region in the optical propagation direction; the third modulation segment has a third length, which is the sum of the electrode lengths in the third modulation segment where the second modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region in the optical propagation direction; the effective electrode length of the first mode is the first length; the effective electrode length of the second mode is the sum of the second length and the third length; the effective electrode length of the third mode is the sum of the first length, the second length, and the third length; wherein the effective electrode length of the third mode is greater than the effective electrode length of the second mode, and the effective electrode length of the second mode is greater than the effective electrode length of the first mode.

[0008] In some embodiments, the fiber optic gyroscope chip further includes an on-chip optical path functional module; the integrated optical waveguide structure includes at least a first optical port, a second optical port, a third optical port, and a fourth optical port; the first optical port is connected to the light source of the fiber optic gyroscope, the second optical port is connected to the detector fiber of the fiber optic gyroscope, and the third and fourth optical ports are used to connect to the two ends of the polarization-maintaining fiber ring, respectively; the on-chip optical path functional module is disposed between the first and second optical ports and the third and fourth optical ports, and the on-chip optical path functional module includes at least a first multimode interference coupler, a polarization rotation beam splitter, and a second multimode interference coupler connected in sequence.

[0009] In some embodiments, a first multimode interference coupler is configured to split the incident light from the light source into a polarization rotating beam splitter and to combine the interference light returning from the polarization-maintaining fiber ring into a second optical port; the polarization rotating beam splitter is configured to rotate the polarization state of the optical signal and split the polarization beam; and a second multimode interference coupler is configured to split the optical signal from the polarization rotating beam splitter and to combine the optical signals returning from both ends of the polarization-maintaining fiber ring through interference.

[0010] In some embodiments, the fiber optic gyroscope chip further includes: a substrate layer, on which a thin-film lithium niobate layer is disposed; a cladding layer covering the integrated optical waveguide structure; and a metal electrode layer, including at least multiple segments of optoelectronic modulation structure, disposed on the cladding layer.

[0011] This application provides a fiber optic gyroscope system, comprising at least the aforementioned fiber optic gyroscope chip, light source, detector, polarization-maintaining fiber loop, and control circuit. The light source is connected to a first optical port in the fiber optic gyroscope chip via an optical fiber. The detector is connected to a second optical port in the fiber optic gyroscope chip via an optical fiber. The two ends of the polarization-maintaining fiber loop are respectively connected to a third optical port and a fourth optical port in the fiber optic gyroscope chip. The control circuit is electrically connected to multiple optoelectronic modulation structures in the fiber optic gyroscope chip to drive each optoelectronic modulation structure to be turned on or off, thereby obtaining multiple modulation structures with different effective electrode lengths and modulation modes corresponding to each modulation structure. This enables multi-level reconfigurable switching of the fiber optic gyroscope's phase modulation sensitivity and linear range, and demodulates the signal output by the detector to obtain angular velocity information.

[0012] In some embodiments, the control circuit includes at least: a modulation drive unit configured to generate a drive voltage signal or a drive current signal applied to each segment of the photoelectric modulation structure; a mode control unit configured to select a modulation mode based on the current angular velocity information or the system operating state, and control the modulation drive unit to output the corresponding drive voltage signal or drive current signal based on the modulation mode; an analog front-end unit configured to amplify and filter the analog signal output by the detector to obtain a processed signal; an analog-to-digital conversion unit configured to perform analog-to-digital conversion on the processed signal to obtain a digital signal; and a demodulation and data processing unit configured to calculate angular velocity information based on the digital signal.

[0013] In some embodiments, a first angular velocity threshold and a second angular velocity threshold are preset in the control circuit; the modulation mode includes at least a first mode, a second mode, and a third mode, each mode corresponding to a pre-calibrated scaling factor; the demodulation and data processing unit is further configured to demodulate the digital signal based on the current modulation mode of the fiber optic gyroscope chip to obtain demodulated data; the demodulation and data processing unit is further configured to convert the demodulated data based on the scaling factor corresponding to the current modulation mode to obtain current angular velocity information; the mode control unit is further configured to adjust the modulation mode based on the current angular velocity information, the first angular velocity threshold, and the second angular velocity threshold. Attached Figure Description

[0014] Figure 1 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 1 ; Figure 2 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 2 ; Figure 3 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 3 ; Figure 4 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 4 ; Figure 5 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 5 ; Figure 6 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 6 ; Figure 7 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 7 ; Figure 8This is an optional structural schematic diagram of the fiber optic gyroscope system provided in an embodiment of this application.

[0015] It should be noted that the terms "first" and "second" mentioned above are only used to distinguish between different options and do not represent the degree of superiority or inferiority of the options or their priority in the implementation process. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] It should be understood that the following description of the embodiments is intended to explain and illustrate the overall concept of the embodiments of this application, and should not be construed as limiting the embodiments of this application. In the specification and drawings, the same or similar reference numerals refer to the same or similar parts or components. For clarity, the drawings are not necessarily drawn to scale, and some well-known parts and structures may be omitted in the drawings.

[0018] In some embodiments, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the meaning understood by a person skilled in the art to which the embodiments of this application pertain. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The word "a" or "an" does not exclude multiple components. The terms "comprising" or similar terms mean that the element or object preceding the word covers the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects. The terms "connected" or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Above," "below," "left," "right," "top," or "bottom," etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described object changes. When an element such as a layer, film, region, or substrate is referred to as being "above" or "below" another element, the element may be located "directly" above or below the other element, or there may be intermediate elements present.

[0019] As weaponry and high-dynamic platforms increasingly demand improvements in size, power consumption, and environmental adaptability, integrating key optical paths of fiber optic gyroscopes onto integrated optical platforms such as thin-film lithium niobate has become an important development direction.

[0020] In fiber optic gyroscopes, the system's sensitivity and linear range are closely related to parameters such as the polarization-maintaining fiber loop length, electro-optic modulation depth, operating wavelength, and demodulation method. To improve resolution at small angular velocities, a longer fiber loop and a larger equivalent phase modulation are typically required; however, to prevent modulation saturation and maintain good linearity during launch and maneuvering operations, it is desirable to reduce the modulation depth or equivalent phase gain. A fiber optic gyroscope with a single fixed parameter struggles to simultaneously achieve high sensitivity and a large dynamic range, especially in applications such as tactical missiles where there are both slow attitude adjustments and large angular velocities at launch, this contradiction is even more pronounced.

[0021] To extend the measurement dynamic range, one approach involves configuring two sets of fiber optic gyroscopes or two sets of fiber optic rings, optimized for high-precision, small-range measurements and low-precision, large-range measurements respectively, and then switching or fusing data at the system level. This approach requires multiple optical components and multiple interfaces, resulting in complex structures and large volumes, making it difficult to meet the requirements of integration, miniaturization, and high reliability. Another approach is to achieve "electronic magnification" in a single fiber optic gyroscope by adjusting the electronic amplification factor or changing the demodulation algorithm. However, the effective electrode length and modulation structure of the front-end electro-optic modulator remain unchanged. When the input angular velocity is too large, phase modulation saturation or nonlinear errors can still easily occur, making it difficult to truly improve the usable linear range.

[0022] With the development of thin-film lithium niobate materials and processes, high-speed electro-optic modulators, integrated couplers, and polarization management devices can now be fabricated on this platform for building on-chip fiber optic gyroscopes. However, most related thin-film lithium niobate integration schemes use a single fixed-length electro-optic modulator, whose electrode structure and equivalent modulation length cannot be adjusted after chip manufacturing, providing only a single sensitivity and range characteristic. To obtain multiple ranges, multiple modulators usually need to be connected in series in the optical path or multiple sets of electrodes and drive channels need to be led out, resulting in increased chip area, increased insertion loss, and increased packaging complexity, which is not conducive to engineering applications. At the same time, related integration schemes often do not adequately consider the polarization matching of polarization-maintaining fiber rings and on-chip polarization management, which can easily introduce polarization-dependent drift in large dynamic ranges and complex environments.

[0023] Therefore, the relevant technologies still lack a fiber optic gyroscope integration solution that can achieve multiple reconfigurable modulation lengths on a thin-film lithium niobate integrated chip through structural design and electrode configuration, while taking into account both large dynamic range and high sensitivity, as well as polarization management and simplified packaging, without changing the fiber loop length and external light source.

[0024] To address the problems existing in related technologies, this application provides a large-range fiber optic gyroscope thin-film lithium niobate integrated chip and system based on a reconfigurable multi-segment modulation structure. This chip integrates an optical waveguide structure and a multi-segment optoelectronic modulation structure on a thin-film lithium niobate substrate, and achieves various effective electrode length combinations through segmented connections between a common ground electrode and two signal electrodes. The control circuit selects different modulation modes based on the current angular velocity estimate or system state, thereby achieving multi-level reconfigurable switching of the fiber optic gyroscope's phase modulation sensitivity and linear range without changing the length of the polarization-maintaining fiber loop or the external light source.

[0025] Thus, by setting multiple segments of photoelectric modulation structure on the thin-film lithium niobate layer and selectively driving each segment of electrode to conduct or deactivate through a control circuit, modulation modes with different effective electrode lengths are formed. This achieves multi-level switching of phase modulation sensitivity and linear range. Compared with the single-segment fixed-length modulation structure in related technologies, it can achieve both large dynamic range and high-resolution measurement without changing the length of the polarization-maintaining fiber loop and the external light source, thereby improving the system's ability to adapt to complex operating conditions.

[0026] The technical solution of this application will now be described in detail with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 1 ,like Figure 1 As shown, the fiber optic gyroscope chip 10 provided in this application embodiment may include an integrated optical waveguide structure 101 and a multi-segment optoelectronic modulation structure 102.

[0028] The integrated optical waveguide structure 101 can refer to a waveguide system formed in a thin-film lithium niobate layer for transmitting optical signals. The integrated optical waveguide structure 101 may include a waveguide core region, which can be formed with a specific refractive index distribution through doping or etching to guide the optical signal to propagate along a specific path. The integrated optical waveguide structure can serve as a waveguide channel, not only undertaking the task of transmitting optical signals but also acting as a carrier for electro-optic modulation.

[0029] In some embodiments, the integrated optical waveguide structure 101 can form a high-precision waveguide structure in a thin-film lithium niobate layer through precise process control, such as epitaxial bonding, intelligent stripping, etching, and regrowth, so as to achieve efficient transmission and stable modulation of optical signals.

[0030] In some embodiments, the multi-segment optoelectronic modulation structure 102 is located in the cladding of the thin-film lithium niobate layer. The multi-segment optoelectronic modulation structure 102 is sequentially arranged along the light propagation direction X on the fiber optic gyroscope chip (the optical signal propagates in the X direction in the integrated optical waveguide structure). Each optoelectronic modulation structure (such as the first modulation segment 1021, the second modulation segment 1022, and the third modulation segment 1023) includes electrodes (such as 1021-1, 1021-2, and 1021-3) disposed on both sides 101 of the integrated optical waveguide structure. Each optoelectronic modulation structure is turned on or off under the drive of the control circuit of the fiber optic gyroscope system, resulting in multiple modulation structures with different effective electrode lengths and modulation modes corresponding to each modulation structure, so as to realize multi-level reconfigurable switching of the phase modulation sensitivity and linear range of the fiber optic gyroscope.

[0031] Here, the multi-segment optoelectronic modulation structure 102 is located within the cladding of the thin-film lithium niobate layer; therefore, the multi-segment optoelectronic modulation structure 102 and the integrated optical waveguide structure 101 are not in spatial contact. The multi-segment optoelectronic modulation structure 102 extends along the light propagation direction to ensure effective coupling with the integrated optical waveguide structure 101. The multi-segment optoelectronic modulation structure can be formed by metal sputtering and photolithography etching processes, and connected to the control circuit by flip-chip bonding or wire bonding. The width, spacing, and thickness of each optoelectronic modulation segment can be optimized according to specific application scenarios to meet the requirements of high-frequency modulation and low driving impedance.

[0032] Here, each optoelectronic modulation structure may include a pair of electrodes. Electrodes 1021-1 and 1021-3 of this pair can be electrically connected to a common ground electrode, and electrode 1021-2 can be electrically connected to a signal electrode. The pair of electrodes can be selectively turned on or off according to the drive signal output by the control circuit, thereby changing the actual effective electrode length in the multi-segment optoelectronic modulation structure 102, and thus affecting the phase modulation sensitivity and linear range. In this way, the fiber optic gyroscope system can automatically switch between different modulation modes under different operating conditions to optimize dynamic range and resolution.

[0033] In some embodiments, the modulation mode can refer to the combination of operating states of the multi-segment optoelectronic modulation structure under different signal electrode conduction states. Each mode can correspond to a specific effective electrode length configuration, thereby affecting the modulation sensitivity and linear range of the fiber optic gyroscope chip. The effective electrode length can refer to the total length of the electrodes involved in the modulation in the light propagation direction under a certain modulation mode. Since the electrode arrangement of each optoelectronic modulation structure is different, the effective electrode length will also change under different modulation modes. For example, in the first mode, only the first modulation segment 1021 is in the modulation state, and the effective electrode length is the sum of the interaction electrode lengths that overlap with the waveguide in the first modulation segment 102, resulting in a shorter effective electrode length; while in the third mode, all modulation segments are in the modulation state, resulting in the longest effective electrode length. The above-mentioned variable effective electrode length design allows the fiber optic gyroscope system to use a short electrode length to prevent saturation when measuring large angular velocities, and a long electrode length to improve sensitivity when measuring small angular velocities.

[0034] This application embodiment applies a driving voltage to the signal electrodes through a control circuit, which can selectively activate different modulation segments, thereby changing the effective electrode length and adjusting the modulation mode, improving the system's adaptability and measurement accuracy. The control circuit can refer to an electronic control system used to generate and manage the modulation drive signal and select the modulation mode. The control circuit can switch between modulation modes based on real-time angular velocity information and adjust the amplitude and frequency of the drive signal accordingly to ensure optimal system operation.

[0035] Multi-mode reconfigurable switching refers to the ability of a fiber optic gyroscope system to freely switch between multiple modulation modes through control circuit adjustments. This not only expands the system's dynamic range but also provides optimal measurement performance across different angular velocity ranges. For example, when the fiber optic gyroscope system detects a high angular velocity, it automatically switches to the first mode to prevent modulation saturation; when it detects a low angular velocity or enters the creep measurement phase, it automatically switches to the third mode to improve measurement sensitivity and resolution.

[0036] This application embodiment sets up a multi-segment photoelectric modulation structure on a thin-film lithium niobate layer and selectively drives each segment of the electrode to be turned on or off through a control circuit, thereby forming a modulation mode with different effective electrode lengths. This achieves multi-level switching of phase modulation sensitivity and linear range. Compared with the single-segment fixed-length modulation structure in related technologies, it can achieve both large dynamic range and high-resolution measurement without changing the length of the polarization-maintaining fiber ring and the external light source, thus improving the system's ability to adapt to complex working conditions.

[0037] Figure 2 This is a schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 2,like Figure 2 As shown, the integrated optical waveguide structure includes optical waveguide core regions 1011 and 1012, and the optical waveguide core region is an asymmetric double-ridge waveguide.

[0038] Each optoelectronic modulation structure includes at least one of a first modulation signal electrode 1021-2 connected to the first signal electrode 201 and a second modulation signal electrode (including 1022-2 in the second modulation segment and 1023-2 in the third modulation segment) connected to the second signal electrode 202, and at least one modulation ground electrode (1021-1, 1021-3, 1022-1, 1022-3, 1023-1 and 1023-3) connected to the common ground electrode 203; each optical waveguide core region (1011 or 1012) is provided with one of the first modulation signal electrode and the second modulation signal electrode on both sides, as well as the modulation ground electrode; the common ground electrode 203, the first signal electrode 201 and the second signal electrode 202 are electrically connected to the control circuit, and the first signal electrode 201 and the second signal electrode 202 are configured to be turned on or off under the drive of the control circuit, so that different modulation segments are in the modulation state, thereby forming a modulation mode with different effective electrode lengths, realizing multi-level switching of phase modulation sensitivity and linear range.

[0039] In some embodiments, the asymmetric double-ridge waveguide includes two ridges of different widths or heights, such as 1011 and 1012, for directional propagation and polarization control of optical signals. The unique geometry of the asymmetric double-ridge waveguide optimizes the coupling efficiency and polarization matching capability of the optical signal. For example, in practical applications, the asymmetric double-ridge waveguide can effectively distribute the input optical signal to different arms of the polarization-maintaining fiber ring and ensure good interference during the return journey. Therefore, using an asymmetric double-ridge waveguide as the core region of the optical waveguide helps optimize the optical signal propagation characteristics in the optical path and improves the overall system performance.

[0040] In some embodiments, the asymmetric double-ridge waveguide can be formed by etching on a thin-film lithium niobate material. The asymmetric double-ridge waveguide utilizes the high refractive index contrast and electro-optic effect of the thin-film lithium niobate material to achieve efficient modulation and control of optical signals.

[0041] In the embodiments of this application, each optical waveguide core region 1011 or 1012 is provided with one of a first modulation signal electrode 1021-2 and a second modulation signal electrode (1022-2 and 1023-2) on both sides, as well as a modulation ground electrode. For example, in the first modulation segment 1021, the optical waveguide core region 1011 is provided with the first modulation signal electrode 1021-2 and the modulation ground electrode 1021-1 on both sides, and the optical waveguide core region 1012 is provided with the first modulation signal electrode 1021-2 and the modulation ground electrode 1021-3 on both sides.

[0042] In some embodiments, the first modulation signal electrode 1021-2 and the second modulation signal electrodes 1022-2 and 1023-2 are connected to the first signal electrode 201 and the second signal electrode 202, respectively. The control circuit drives the first signal electrode 201 and the second signal electrode 202 to selectively turn on or off, so that each modulation segment can operate independently in different modulation modes, thereby realizing reconfigurable switching of multiple effective electrode length combinations. Here, the common ground electrode 203 can be used to provide a unified reference potential to ensure the stability and consistency of the modulation signal.

[0043] In this embodiment, by setting multiple modulation signal electrodes and using them in conjunction with modulation ground electrodes, multiple reconfigurable effective electrode length combinations can be achieved, thereby significantly expanding the dynamic range of the system without changing the fiber optic ring length and external light source, while improving the measurement resolution at small angular velocities.

[0044] The embodiments of this application optimize the optical field distribution and improve modulation efficiency through an asymmetric double-ridge waveguide design. At the same time, the segmented electrode structure combined with a common-ground electrode design enables different modulation segments to work independently in different modes, further enhancing the flexibility and controllability of modulation, which is beneficial for reducing power consumption and improving response speed.

[0045] Please continue to refer to Figure 2 The multi-segment optoelectronic modulation structure 102 includes at least a first modulation segment 1021, a second modulation segment 1022, and a third modulation segment 1023. The first modulation segment 1021 includes at least one first modulation signal electrode 1021-2 and at least one modulation ground electrode (such as 1021-1 and 1021-3); the second modulation segment 1022 includes at least one second modulation signal electrode 1022-2 and at least one modulation ground electrode (such as 1022-1 and 1022-3); the third modulation segment 1023 includes at least one second modulation signal electrode 1023-2 and at least one modulation ground electrode (such as 1023-1 and 1023-3).

[0046] In some embodiments, the modulation mode includes at least a first mode, a second mode, and a third mode. When the first signal electrode 201 is turned on and the second signal electrode 202 is turned off, the first modulation segment 1021 is in a modulation working state, and the multi-segment optoelectronic modulation structure 102 is in the first mode; when the first signal electrode 201 is turned off and the second signal electrode 202 is turned on, the second modulation segment 1022 and the third modulation segment 1023 are in a modulation working state, and the multi-segment optoelectronic modulation structure 102 is in the second mode; when both the first signal electrode 201 and the second signal electrode 202 are turned on, the first modulation segment 1021, the second modulation segment 1022, and the third modulation segment 1023 are all in a modulation working state, and the multi-segment optoelectronic modulation structure 102 is in the third mode.

[0047] By designing each modulation segment to have a different length in the direction of light propagation, the first mode obtains the maximum linear range, the third mode obtains the highest modulation sensitivity, and the second mode is in between, thus achieving multiple switchable sensitivity and range.

[0048] In this embodiment, the first signal electrode 201 is responsible for applying a modulation voltage to the first signal electrode, thereby enabling the first modulation segment to generate an electric field in the on state, and this electric field can affect the optical signal in the optical waveguide. The modulation ground electrode, serving as a reference potential point, is connected to one side electrode of the first, second, and third modulation segments respectively to ensure the integrity of the current path. The second modulation signal electrode is connected to the second and third modulation segments respectively, and is used to provide modulation voltage to these two modulation segments.

[0049] here, Figure 3 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 3 ,like Figure 3 As shown, in the first mode, only the first modulation segment 1021 is in a modulation state (represented by the dashed box 301). The signal side electrodes of the second modulation segment 1022 and the third modulation segment 1023 are not connected to the drive signal and only form a static potential with the common ground electrode 203, which is in a non-modulated state. At this time, the equivalent electrode length corresponding to the first mode is the shortest, the corresponding equivalent half-wave voltage Vπ is larger, and the modulation depth is smaller, so that the system still maintains good linearity in a large angular velocity range and is not prone to modulation saturation. It is suitable for angular velocity measurement in the launch phase or large maneuver phase.

[0050] Figure 4 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 4 ,like Figure 4 As shown, in the second mode, the second modulation segment 1022 and the third modulation segment 1023 are in a modulation state (represented by dashed box 401), and the signal-side electrode of the first modulation segment 1021 is not connected to a drive signal, only forming a static potential with the common ground electrode 203, and is in a non-modulated state. The equivalent electrode length corresponding to the second mode is between that of the first mode and the third mode, which is suitable for the medium angular velocity measurement stage. It can reduce the range jump during mode switching and improve the continuity and stability of the system when connecting different working ranges.

[0051] Figure 5 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 5 ,like Figure 5As shown, in the third mode, the first modulation segment 1021, the second modulation segment 1022, and the third modulation segment 1023 are all in a modulation state (represented by dashed box 501). The third mode has the longest equivalent electrode length, obtains the largest phase modulation amount under the same driving voltage, and has the smallest corresponding equivalent Vπ, thus achieving the highest modulation sensitivity. Mode 3 is suitable for small angular velocity and creep measurement scenarios, and can significantly improve measurement resolution. Here, the longer the equivalent length, the smaller the equivalent Vπ, and the greater the phase modulation under the same voltage.

[0052] By reasonably setting the length and connection method of each modulation segment, the embodiments of this application can realize the automatic switching of multiple working modes on a single chip, and significantly expand the dynamic range of the system without changing the length of the polarization-maintaining fiber ring and the external light source.

[0053] This application's embodiments achieve multiple switchable effective electrode lengths by introducing a reconfigurable multi-segment modulation structure and a segmented signal electrode control mechanism. By introducing this reconfigurable multi-segment modulation structure and segmented signal electrode control mechanism, both a large dynamic range and high sensitivity measurement are achieved without changing the polarization-maintaining fiber loop length or the external light source.

[0054] In some embodiments, the first modulation segment 1021 has a first length L1, which is the sum of the electrode lengths in the first modulation segment where the first modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region (i.e., the electrode and the waveguide overlap) in the optical propagation direction; the second modulation segment 1022 has a second length L2, which is the sum of the electrode lengths in the second modulation segment where the second modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region in the optical propagation direction; and the third modulation segment 1023 has a third length L3, which is the sum of the electrode lengths in the third modulation segment where the second modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region in the optical propagation direction.

[0055] Here, the interaction between the electrode and the optical waveguide core region can refer to the effective electro-optic effect generated between the electrode and the optical waveguide core region. Due to the excellent electro-optic properties of the thin-film lithium niobate material, the electric field distributed between the electrodes will change the refractive index of the optical signal in the waveguide, thereby achieving phase modulation of the optical signal. The effective length of each modulation segment determines the phase modulation depth of the modulation segment under a specific driving voltage.

[0056] In some embodiments, the design of the modulation segment needs to consider factors such as the width of the waveguide core region, the electrode spacing, and the electrode coverage area to ensure that the electric field can act uniformly on the entire waveguide region, avoiding modulation nonlinearity or efficiency degradation caused by uneven electric field distribution. Furthermore, the length of the modulation segment directly affects its equivalent half-wave voltage Vπ; the shorter the length, the larger Vπ, and vice versa. Therefore, in the large angular velocity measurement stage, a shorter modulation segment can be selected to prevent modulation saturation and improve the linear range of the system. The equivalent half-wave voltage Vπ can refer to the minimum driving voltage required in an electro-optic modulator to achieve a phase change of π radians (i.e., half a wavelength) in the optical signal.

[0057] In some embodiments, the effective electrode length of the first mode is a first length L1; the effective electrode length of the second mode is the sum of the second and third lengths L2+L3; and the effective electrode length of the third mode is the sum of the first, second, and third lengths L1+L2+L3. The effective electrode length of the third mode is greater than that of the second mode, and the effective electrode length of the second mode is greater than that of the first mode, i.e., L1 < L2+L3 < L1+L2+L3. Therefore, the first mode is suitable for the large angular velocity measurement stage; the second mode is suitable for the medium angular velocity measurement stage; and the third mode is suitable for the small angular velocity and creep measurement stages. This results in different effective electrode lengths and modulation sensitivities when different combinations of conduction are applied.

[0058] This application embodiment ensures that the effective electrode length varies in different modes by cascading multiple modulation segments and selectively enabling them in different modes. This guarantees the differences in sensitivity and linear range of each mode, enabling the system to automatically select the optimal mode based on the current angular velocity, thereby improving overall performance and adaptability.

[0059] In some embodiments, Figure 6 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 6 ,like Figure 6 As shown, the fiber optic gyroscope chip 10 also includes an on-chip optical path functional module 103; the integrated optical waveguide structure includes at least a first optical port 1, a second optical port 2, a third optical port 1, and a fourth optical port 4; the first optical port 1 is connected to the light source of the fiber optic gyroscope, the second optical port 2 is connected to the detector fiber of the fiber optic gyroscope, and the third optical port 3 and the fourth optical port 4 are used to connect to the two ends of the polarization-maintaining fiber ring, respectively; the on-chip optical path functional module 103 is disposed between the first optical port 1 and the second optical port 2 and the third optical port 3 and the fourth optical port 4, and the on-chip optical path functional module 103 includes at least a first multimode interference coupler 1031, a polarization rotation beam splitter 1032, and a second multimode interference coupler 1033 connected in sequence.

[0060] Here, the on-chip optical path function module 103 can be an optical element integrated inside the fiber optic gyroscope chip 10, used to perform functions such as beam splitting, beam combining, and polarization management of optical signals. The on-chip optical path function module 103 can effectively reduce the use of external optical components, thereby reducing system insertion loss and packaging complexity. For example, by splitting the optical signal input from the light source into two paths and sending them to the two ports of the polarization-maintaining fiber ring respectively, and then combining the returning optical signals and outputting them to the detector, the on-chip optical path function module 103 not only improves the stability of the system, but also enhances the ability to suppress polarization-related errors.

[0061] In some embodiments, the on-chip optical path function module 103 is used to realize incident light beam splitting, echo beam combining, polarization matching / rotation, and coil arm allocation.

[0062] The four optical ports in this embodiment enable the fiber optic gyroscope chip to efficiently interface with external optical systems, ensuring a clear and stable transmission path for the optical signal. For example, the first optical port 1 receives incident light from the light source, the second optical port 2 outputs the returned light signal after interference processing, and the third optical port 3 and the fourth optical port 4 connect the two ends of the polarization-maintaining fiber ring to form a Sagnac interference circuit. Through the design of the first optical port 1, the second optical port 2, the third optical port 3, and the fourth optical port 4, effective modulation and detection of the optical signal can be achieved without changing the external light source and the fiber ring.

[0063] This application embodiment integrates functions such as beam splitting, beam combining, and polarization management onto the same chip, reducing reliance on external optical devices and improving overall stability and reliability.

[0064] In some embodiments, the first multimode interference coupler 1031 is configured to power-split the incident light from the light source and input it to a polarization rotating beam splitter, and to combine the interference light returning from the fiber-storage ring and couple it to a second optical port. This is used to filter out the TM mode from the on-chip optical waveguide mode, retaining only the TE mode.

[0065] The first multimode interference coupler 1031 can be a passive optical device for realizing optical signal beam splitting and combining. It distributes the input light uniformly to two output ports through multimode interference. In this embodiment, the first multimode interference coupler 1031 is located near the first optical port 1 and the second optical port 2. One end of it is connected to the first optical port 1 and the second optical port 2 via optical waveguides, and the other end is connected to the polarization rotating beam splitter 120. It first splits the incident light from the light source into two paths, which are then transmitted to different input ports of the polarization rotating beam splitter 1032. When the optical signal returns from the polarization-maintaining fiber ring, the first multimode interference coupler 1031 acts as a beam combiner, merging the optical signals from different paths and outputting them to the second optical port 2. Using the first multimode interference coupler 1031 for beam splitting and combining effectively reduces optical path loss and improves system stability.

[0066] Here, the first multimode interference coupler can be made of thin-film lithium niobate material, which has low insertion loss, high beam splitting ratio, and good temperature stability. In the integrated chip, the first multimode interference coupler can be designed as a 1×2 structure, which ensures that the optical signal maintains a high signal-to-noise ratio and consistency during splitting and combining.

[0067] In some embodiments, the polarization rotating beam splitter 1032 is configured to rotate and polarize the polarization state of an optical signal.

[0068] The polarization-rotating beam splitter 1032 is a device used to process the polarization state of an optical signal. Its function is to rotate the polarization of the optical signal during its round-trip propagation and perform polarization beam splitting based on the polarization direction. The polarization-rotating beam splitter 1032 is positioned between the first multimode interference coupler 1031 and the second multimode interference coupler 1033. It converts the optical signal from the first multimode interference coupler 1031 into a polarization state (such as TE mode) that matches the main axis of the polarization-maintaining fiber ring, ensuring stable transmission of the optical signal in the polarization-maintaining fiber. When the optical signal returns from the polarization-maintaining fiber ring, the polarization-rotating beam splitter rotates and splits the polarization state of the optical signal again, thereby reducing system errors caused by polarization mismatch.

[0069] The polarization-rotating beam splitter 1032 can be implemented based on an asymmetric ridge waveguide structure, utilizing adiabatic gradient technology to achieve polarization rotation. The design of the polarization-rotating beam splitter based on the asymmetric ridge waveguide structure not only improves the transmission efficiency of optical signals but also effectively suppresses measurement errors caused by polarization-dependent drift.

[0070] In some embodiments, the second multimode interference coupler 1033 is configured to split the optical signal from the polarization rotating beam splitter and to interfere and combine the optical signals returned from both ends of the polarization-maintaining fiber loop.

[0071] The second multimode interference coupler 1033 can be a passive optical device based on the principle of multimode interference. It is used to further split the optical signal from the polarization-rotating beam splitter and complete the interference beam combining operation when the optical signal returns from the polarization-maintaining fiber ring. For example, one side of the second multimode interference coupler 1033 is connected to the polarization-rotating beam splitter 1032, and the other side is connected to the third optical port 3 and the fourth optical port 4 through optical waveguides, respectively. It is used to recombine the optical signals from both ends of the polarization-maintaining fiber ring according to a specific ratio, form an interference signal, and output it to the detector port, i.e., the second optical port 2.

[0072] The design of the second multimode interference coupler 1033 is similar to that of the first multimode interference coupler 1031. It can also adopt a 1×2 structure and has advantages such as low loss, high beam splitting ratio, and good temperature stability. In addition, the second multimode interference coupler 1033 can also optimize the interference effect by adjusting the waveguide width and length, thereby improving the overall performance of the system.

[0073] Through the on-chip optical path function module 103, the optical path between the first optical port 1 and the second optical port 2 forms a complete beam splitting, polarization management and interference beam combining function inside the chip, thereby forming a stable Sagnac interference structure with the external polarization-maintaining fiber ring.

[0074] This application embodiment achieves efficient beam splitting and combining of optical signals through the combined use of a multimode interference coupler and a polarization rotating beam splitter, and precisely manages the polarization state, reducing polarization-related errors and improving the measurement accuracy and stability of the system.

[0075] In some embodiments, Figure 7 A schematic diagram of an optional structure of the fiber optic gyroscope chip provided in the embodiments of this application. Figure 7 ,like Figure 7 As shown in Figure a, Figure a is a schematic diagram of the electro-optic modulation structure of the fiber optic gyroscope chip without segmented electrodes; Figure b is a schematic diagram of the multi-segment electro-optic modulation structure of the fiber optic gyroscope chip with segmented electrodes. Taking Figure b as an example, the fiber optic gyroscope chip also includes a substrate layer 701, a thin-film lithium niobate layer 702 disposed on the substrate layer 701; a cladding layer 703 covering the integrated optical waveguide structure 101; and a metal electrode layer 704, including at least multiple optoelectronic modulation structures, disposed on the cladding layer 703. The metal electrode layer 704 includes a common ground electrode 203, a first signal electrode 201, and a second signal electrode 202, and the electrode connection relationship of each modulation segment is formed by metal traces.

[0076] In the embodiments of this application, as shown in Figure a, the chip without segmented electro-optic modulation structure does not have a metal electrode layer 704.

[0077] Substrate layer 701 is a base layer used to support the thin film material and can be made of silicon substrate or other materials with high thermal stability and mechanical strength. The function of the substrate layer is to provide a stable physical support platform, ensuring that the thin film lithium niobate layer can be uniformly attached to the substrate surface and maintain good optical waveguide performance. In addition, the substrate layer can also serve as the packaging base for integrated devices, improving the stability and reliability of the overall structure. The substrate material in the embodiments of this application may include silicon (Si), sapphire (Al2O3), and silicon dioxide (SiO2).

[0078] The thin-film lithium niobate layer 702 refers to a thin film of lithium niobate crystal deposited on a substrate. Thin-film lithium niobate layers exhibit excellent electro-optic effects and are commonly used in the fabrication of high-performance optoelectronic devices, such as electro-optic modulators, optical switches, and sensors. The thin-film lithium niobate layer 702 can be formed through epitaxial growth or smart lift-off techniques, and its thickness is typically between a few micrometers and tens of micrometers. The function of the thin-film lithium niobate layer is to modulate the phase of optical signals under the influence of an external electric field, thereby achieving control and processing of optical signals. In the embodiments of this application, the thin-film lithium niobate layer serves as the primary optical waveguide material, used to construct an integrated optical path and to support multiple multi-segment optoelectronic modulation structures to achieve reconfigurable modulation functionality.

[0079] Cladding 703 can be a dielectric layer used to encapsulate and protect the optical waveguide structure. It can be made of a low-refractive-index material, such as silicon dioxide (SiO2), silicon nitride (Si3N4), or a polymer. Cladding 703 restricts the propagation path of light in the optical waveguide, reduces optical loss, and prevents interference from the external environment. Simultaneously, the cladding provides a flat surface for the subsequent metal electrode layer, facilitating precise fabrication and wiring of the metal electrode layer. For example, in the embodiments of this application, cladding 703 covers the integrated optical waveguide structure 101, providing isolation and protection, enabling the optical waveguide to operate in a stable environment and preventing performance degradation due to external temperature changes, mechanical stress, or chemical corrosion. Different cladding materials can be selected for different application scenarios; for example, silicon dioxide cladding is suitable for high-speed communication systems, while polymer cladding is suitable for flexible devices.

[0080] In some embodiments, the cladding 703 not only serves a protective function but also has a certain coupling relationship with the metal electrode layer 704. Since the metal electrode layer 704 may require patterning on the cladding 703, the flatness and dielectric properties of the cladding directly affect the distribution accuracy and modulation efficiency of the metal electrode layer. Therefore, during chip design, the layout and size of the metal electrode layer must be optimized based on the selected cladding material to ensure optimal modulation performance.

[0081] In some embodiments, the metal electrode layer 704 can be a conductive layer made of a metallic material, such as aluminum (Al), gold (Au), copper (Cu), or an alloy of metallic materials. The metal electrode layer is used to apply an electric field to drive the electro-optic modulation process in the optical waveguide. A multi-segment opto-modulation structure can refer to dividing the entire modulation region into multiple independent modulation segments, each equipped with a pair of electrodes. By controlling the conduction state of each segment's electrodes, the modulation length can be flexibly switched. This structural design can significantly improve the system's dynamic range and sensitivity, making it adaptable to different angular velocity measurement requirements.

[0082] Here, the design of a multi-segment optoelectronic modulation structure requires comprehensive consideration of the refractive index distribution of the optical waveguide and the electric field distribution of the metal electrode layer. To ensure that each modulation region can operate independently without interfering with each other, the spacing and width between the electrodes need to be precisely calculated to avoid crosstalk.

[0083] This application's embodiments, by introducing structures such as a substrate layer, a thin-film lithium niobate layer, a cladding layer, and a metal electrode layer into the fiber optic gyroscope chip, can effectively improve the chip's integration and performance. By constructing a complete integrated optical path and electrode structure on the substrate layer, a highly integrated fiber optic gyroscope chip is achieved, which helps reduce size, lower cost, and improve manufacturing yield; it can also enhance the stability and anti-interference capability of the optical waveguide, thereby reducing insertion loss and polarization-dependent errors, and ultimately enabling a wider dynamic range and higher measurement accuracy.

[0084] This application provides another fiber optic gyroscope system. Figure 8 An optional structural schematic diagram of the fiber optic gyroscope system provided in the embodiments of this application is shown below. Figure 8 As shown, the fiber optic gyroscope system 80 includes at least a fiber optic gyroscope chip 801, a light source 802, a detector 803, a polarization-maintaining fiber optic ring 804, and a control circuit 805.

[0085] In this system, the light source 802 is connected to the first optical port 1 of the fiber optic gyroscope chip 801 via an optical fiber; the detector 803 is connected to the second optical port 2 of the fiber optic gyroscope chip 801 via an optical fiber; the two ends of the polarization-maintaining fiber loop 804 are connected to the third optical port 3 and the fourth optical port 4 of the fiber optic gyroscope chip 801, respectively; and the control 805 is electrically connected to multiple photoelectric modulation structures (e.g., to the first signal electrode 201, the second signal electrode 202, and the common ground electrode 203) in the fiber optic gyroscope chip 801, respectively, to drive each photoelectric modulation structure to be turned on or off, thereby obtaining multiple modulation structures with different effective electrode lengths and modulation modes corresponding to each modulation structure. This enables multi-level reconfigurable switching of the phase modulation sensitivity and linear range of the fiber optic gyroscope, and demodulates the signal output by the detector to obtain angular velocity information.

[0086] In this embodiment, the light source 802 can be a broadband spontaneous emission light source or a wide linewidth semiconductor light source to reduce coherent noise; the detector 803 can be a photodiode or a transimpedance amplifier module to realize the electrical signal conversion of interference light intensity.

[0087] In some embodiments, the control and signal processing circuitry is configured to automatically switch between the first mode, the second mode, and the third mode based on the currently measured absolute value of the angular velocity or the system operating state, in order to extend the dynamic range and improve the resolution of small angular velocities while ensuring linearity.

[0088] In some embodiments, the control circuit includes at least: a modulation drive unit, a mode control unit, an analog front-end unit, an analog-to-digital converter unit, and a demodulation and data processing unit. The modulation drive unit is configured to generate a drive voltage signal or a drive current signal applied to each segment of the photoelectric modulation structure; the mode control unit is configured to select a modulation mode based on the current angular velocity information or the system operating state, and control the modulation drive unit to output the corresponding drive voltage signal or drive current signal based on the modulation mode; the analog front-end unit is configured to amplify and filter the analog signal output by the detector to obtain a processed signal; the analog-to-digital converter unit is configured to perform analog-to-digital conversion on the processed signal to obtain a digital signal; and the demodulation and data processing unit is configured to calculate the angular velocity information based on the digital signal.

[0089] The modulation drive unit is a submodule of the control circuit. It generates appropriate drive signals (voltage or current) according to system requirements to control the conduction state of each segment of the optoelectronic modulation structure, thereby achieving different modulation modes. The drive signal output by the modulation drive unit can be a sine wave, square wave, or other form of periodic waveform. The frequency of these drive signals is matched with the demodulation algorithm to achieve phase modulation. For example, in the low angular velocity measurement stage, the modulation drive unit outputs a higher amplitude drive signal to improve sensitivity; while in the high angular velocity stage, it outputs a lower amplitude drive signal to prevent saturation.

[0090] The mode control unit determines the modulation mode to be used based on the real-time acquired angular velocity estimate or the stage of the system task. For example, when measuring large angular velocities, a modulation mode with a short effective electrode length (i.e., the first mode) is selected to prevent modulation saturation; when measuring small angular velocities, a modulation mode with a long effective electrode length (i.e., the third mode) is selected to improve resolution. The mode control unit can be implemented by a microcontroller or programmable logic device, possessing fast response and adaptive capabilities.

[0091] In some embodiments, the mode control unit and the modulation drive unit have a close cooperative relationship. For example, after the mode control unit sets the target modulation mode according to the current system operating state, it sends a command to the modulation drive unit. The modulation drive unit then generates a drive signal that meets the requirements of the target modulation mode based on the received command. Therefore, the modulation drive unit and the mode control unit need to maintain a good interface design at both the hardware and software levels to ensure the timeliness and accuracy of control signal transmission.

[0092] The analog front-end unit performs preliminary processing on the raw analog signal output from the detector, mainly including amplification and filtering. The analog front-end unit amplifies the signal amplitude and adjusts it to a level suitable for subsequent analog-to-digital conversion; it also filters out noise and interference components to ensure signal quality. For example, during high-speed sampling, high-frequency noise may be introduced; the analog front-end unit uses a low-pass filter to remove this high-frequency noise.

[0093] The analog-to-digital converter (ADC) converts the analog signal output from the analog front-end unit into a digital signal for subsequent digital processing. ADCs can have high sampling rates and resolutions to meet the accuracy requirements of fiber optic gyroscope systems. For example, in high-precision measurement applications, an ADC with 16 bits or more may be needed to ensure sufficient resolution.

[0094] The demodulation and data processing unit is the core of the control circuit. Its main function is to execute a closed-loop demodulation algorithm, converting the digital signal into angular velocity information. The mode control unit can then use this angular velocity information to change the modulation mode. The demodulation and data processing unit can employ methods such as digital phase-locked amplification, quadrature demodulation, or phase tracking to process the input signal based on calibration parameters and temperature compensation data, ultimately outputting an estimated angular velocity value Ω. Furthermore, the demodulation and data processing unit can also perform data filtering and error correction functions to further improve measurement accuracy.

[0095] Through the efficient operation of the demodulation and data processing units, the system can acquire accurate angular velocity information in real time and dynamically adjust the current modulation mode.

[0096] This application embodiment achieves precise control and signal processing of the multi-segment optoelectronic modulation structure in the fiber optic gyroscope chip by setting up a modulation drive unit, a mode control unit, an analog front-end unit, an analog-to-digital conversion unit, and a demodulation and data processing unit. It can realize automatic switching of multiple reconfigurable modulation modes, thereby expanding the dynamic range of the system and improving measurement accuracy without changing the fiber optic ring length and external light source. It can adapt to various application scenarios, especially the needs of high dynamic and miniaturized platforms.

[0097] In some embodiments, a first angular velocity threshold T1 and a second angular velocity threshold T2 can be preset in the control circuit, wherein the first angular velocity threshold is less than the second angular velocity threshold; the modulation mode includes at least a first mode, a second mode, and a third mode, each mode corresponding to a pre-calibrated scaling factor; the demodulation and data processing unit is further configured to demodulate the digital signal based on the current modulation mode of the fiber optic gyroscope chip to obtain demodulated data; the demodulation and data processing unit is further configured to convert the demodulated data based on the scaling factor corresponding to the current modulation mode to obtain current angular velocity information; the mode control unit is further configured to adjust the modulation mode based on the current angular velocity information, the first angular velocity threshold, and the second angular velocity threshold.

[0098] The scaling factor is a scaling factor for each modulation mode, used to convert the demodulated raw data into current angular velocity information. Because the effective electrode lengths differ between modulation modes, the phase modulation depths also differ. Therefore, it is necessary to calibrate the corresponding scaling factor for each modulation mode to ensure accurate current angular velocity information can be obtained under various modulation modes. The scaling factor can be obtained through calibration. During factory or experimental calibration, a known angular velocity (turntable or known Earth rotation component / equivalent input) is applied, and the scaling factor corresponding to each mode is fitted under different modulation modes. Examples include sensitivity coefficients K1 / K2 / K3 and a temperature coefficient. These are written to non-volatile memory and read by the demodulation and data processing unit during operation. The corresponding K value is selected based on the current mode for angular velocity conversion, and temperature compensation is performed in conjunction with the temperature sensor output, thereby improving system accuracy and long-term stability. For example, storing Ki(T) = Ki0 + ai·(T) During operation, the temperature sensor T is read, Ki(T) is calculated according to the current mode i, and the compensated angular velocity is obtained by Ω=Qi / Ki(T), where Qi is the demodulated output / feedback quantity of this mode.

[0099] In different modes, the demodulation process uses the corresponding scaling factor to convert the output voltage or digital quantity into the actual angular velocity value.

[0100] Here, the first angular velocity threshold and the second angular velocity threshold are used to divide the angular velocity into different ranges, thereby determining which modulation mode to use. The absolute value of the angular velocity can be compared with the first angular velocity threshold T1 and the second angular velocity threshold T2. For example, the first angular velocity threshold T1 can be set as the upper limit of the small angular velocity range, and the second angular velocity threshold T2 can be set as the lower limit of the large angular velocity range. When the detected angular velocity is less than T1 (i.e., |Ω| < T1), the mode control unit selects the third mode, simultaneously driving the first signal electrode 201 and the second signal electrode 202 to conduct, making the effective electrode length L1 + L2 + L3 to obtain the highest sensitivity and the minimum measurable angular velocity. When the angular velocity is between T1 and T2 (i.e., T1 ≤ |Ω| < T2), the mode control unit selects the second mode, driving only the second signal electrode 202 to conduct, making the effective electrode length L2 + L3, to balance linearity and sensitivity within a moderate range. When the angular velocity is greater than or equal to T2 (i.e., |Ω| ≥ T2), the mode control unit selects the first mode, driving only the first signal electrode 201 to conduct, making the effective electrode length L1, to obtain the maximum linear range. After setting the first and second angular velocity thresholds in the system, the modulation structure can be dynamically adjusted according to the actual operating conditions to adapt to different measurement requirements.

[0101] The demodulation process in the demodulation and data processing unit refers to the process of converting the digital signal acquired by the detector into an electrical signal reflecting the current angular velocity information and removing noise interference. Demodulation processing depends on the modulation mode currently used because the phase modulation method and feedback mechanism in the optical path differ under different modulation modes. Therefore, the appropriate demodulation algorithm must be selected according to the modulation mode. For example, in the first mode, due to the lower modulation depth, the demodulation algorithm may focus on maintaining linearity; while in the third mode, due to the higher modulation depth, the demodulation algorithm focuses more on improving resolution.

[0102] The demodulation and data processing unit converts the demodulated data into actual current angular velocity information based on a scaling factor according to a specific ratio. Since the system sensitivity varies under different modulation modes, the scaling factor will change accordingly. Therefore, the scaling factor corresponding to the currently used modulation mode must be selected for calculation. For example, in the first mode, the scaling factor K1 is smaller and suitable for measuring large angular velocities; while in the third mode, the scaling factor K3 is larger and suitable for measuring small angular velocities and high precision.

[0103] The mode control unit monitors the current angular velocity in real time and compares it with preset first and second angular velocity thresholds. If the current angular velocity exceeds the second threshold, the system switches to the first mode to prevent modulation saturation and maintain linearity; if the current angular velocity is below the first threshold, it switches to the third mode to improve measurement sensitivity and resolution; if the current angular velocity is between the first and second thresholds, the second mode is used to achieve a balance between sensitivity and linearity.

[0104] In some embodiments, to avoid jitter or instability caused by frequent switching, a hysteresis zone can be set at the negative threshold, so that mode switching is only performed when the current angular velocity meets the condition for a continuous period of time. For example, different entry and exit thresholds can be used when switching modes, or a time filtering condition can be added so that switching is only allowed after the current mode has been maintained for a certain period of time. For example, let the entry threshold T1_in = 10° / s and the exit threshold T1_out = 15° / s; the switch from the first or second mode to the third mode is only performed when |Ω| is less than 10° / s for 100 ms consecutively; when switching back, the switch from the third mode is only performed when |Ω| is greater than 15° / s for 100 ms consecutively. This can avoid frequent switching due to jitter near the threshold.

[0105] This application embodiment achieves multi-level reconfigurable functionality in the current angular velocity measurement system by setting multiple angular velocity thresholds in the control circuit and combining them with scaling factors under different modulation modes. Because multiple angular velocity thresholds are set in the control circuit and combined with scaling factors under different modulation modes, the system can dynamically adjust the modulation structure to adapt to different operating conditions. This dynamic adjustment of the modulation structure can avoid modulation saturation over a large angular velocity range and improve resolution over a small angular velocity range. In this way, the system can balance measurement accuracy and dynamic range, thereby improving the overall performance of the fiber optic gyroscope.

[0106] This application embodiment further provides a method for measuring angular velocity using a reconfigurable multi-segment modulation structure. This method can be executed by software programs or hardware logic in a control circuit. The method selects a first mode during system startup and large maneuvering phases to obtain a large linear range (the large maneuvering phase can be determined by |Ω|≥T2, or triggered by a host computer task phase signal); selects a second mode when the angular velocity enters a preset medium range (the medium range corresponds to |Ω| being between the first threshold T1 and the second threshold T2); and selects a third mode when the angular velocity is in a preset small range or when high-precision creep measurement is required to improve measurement sensitivity and resolution. The mode selection can be automatically completed by the control and signal processing circuit (i.e., the control circuit). The method may include steps S1 to S6: Step S1: System initialization.

[0107] Power is supplied to the light source to ensure stable operation; the detector and analog front-end circuit are started; the control circuit is initialized, loading the scaling factors and temperature compensation parameters corresponding to the first, second, and third modes, and setting the mode switching thresholds T1 and T2, as well as the hysteresis parameter. Initially, the system can default to operating in the first mode to ensure that modulation saturation does not occur under potential large angular velocity disturbances.

[0108] Step S2: Modulation signal output and optical path excitation.

[0109] The control modulation drive unit outputs a modulation signal of a predetermined waveform, such as a sine wave or a square wave, to the first signal electrode and / or the second signal electrode to drive the electro-optic modulation structure on the thin-film lithium niobate integrated chip. The frequency of the output modulation signal is matched with the demodulation algorithm to realize phase modulation and closed-loop demodulation of the fiber optic gyroscope. In the initial mode, such as the first mode, the modulation signal is provided only to the first signal electrode, so that the first modulation segment is in a modulated state, while the second and third modulation segments are in a non-modulated state.

[0110] Step S3: Detection and Demodulation.

[0111] The detector receives the interference light output from the second optical port and outputs the corresponding analog electrical signal. The analog front-end amplifies and filters this signal, and the analog-to-digital converter (ADC) samples it to obtain a digital signal. The demodulation and data processing unit acquires the digital sequence (or equivalent sampled values) of the analog front-end output after ADC sampling, and performs synchronous demodulation / phase-locked loop / closed-loop calculations accordingly, outputting angular velocity information Ω and mode switching criteria. Based on the current operating mode, the demodulation and data processing unit uses a predetermined demodulation algorithm (such as quadrature demodulation, digital phase-locked amplification, or closed-loop phase tracking) to obtain an intermediate quantity proportional to the angular velocity, and uses the scaling factor in this mode to convert it into an instantaneous estimate of the angular velocity Ω. During demodulation, phase feedback can be combined to achieve zero-bias suppression and range extension, while the temperature sensor output is used to compensate for the scaling factor and zero bias in real time.

[0112] Step S4: Mode selection and switching.

[0113] Based on the estimated angular velocity Ω and its absolute value |Ω| obtained in step S3, the demodulation and data processing unit and the mode control unit work together to judge the rationality of the current mode: if the current mode is the first mode and |Ω| is less than the first angular velocity threshold T1 for several consecutive sampling periods, the system is determined to have entered the small angular velocity working range. The mode control unit issues a switching command to switch the working mode to the third mode and drives the first signal electrode and the second signal electrode to conduct simultaneously.

[0114] If the system is currently in the third mode and |Ω| exceeds the second angular velocity threshold T2 for several consecutive sampling periods, it is determined that the system has entered the high angular velocity operating range. The mode control unit issues a switching command to switch the operating mode to the first mode, driving only the first signal electrode to conduct. If the system is currently in the first or third mode and |Ω| is between T1 and T2 for a certain period of time, it can switch to the second mode, driving only the second signal electrode to conduct, making the effective electrode length L2 + L3 to balance linear range and sensitivity. In the above process, different hysteresis intervals can be set for entry and exit thresholds, or time filtering conditions can be introduced to avoid frequent mode switching due to noise or short-term disturbances.

[0115] Step S5: Output and Record.

[0116] In any mode, the demodulation and data processing unit takes the estimated angular velocity value for the current mode, applies temperature compensation and filtering, and outputs it as the system's angular velocity information. This information can be used for navigation calculations, attitude control, or other higher-level systems. Simultaneously, the angular velocity output along with the corresponding operating mode information can be recorded or output for subsequent analysis and diagnostics.

[0117] Step S6: Optional data processing.

[0118] During certain operational phases, two modes can be used alternately within a short time window, such as rapidly switching between a second and a third mode, to acquire angular velocity measurements under different effective electrode lengths. By performing linear fitting, bias estimation, and weighted fusion on the measurement results from the two modes, the accuracy and robustness of the system can be further improved. In this embodiment, this step is optional and is used to illustrate that this application has the capability to perform multi-mode data fusion.

[0119] This application provides a large-range fiber optic gyroscope thin-film lithium niobate integrated chip based on a reconfigurable multi-segment modulation structure, its application system, and angular velocity measurement method. It realizes the achievement of multiple switchable effective modulation lengths on a single thin-film lithium niobate integrated chip through electrode configuration; it balances large dynamic range and high-resolution measurement of small angular velocities without changing the polarization-maintaining fiber loop length and external light source; and it reduces system packaging complexity and improves overall stability and reliability through on-chip polarization management and integration with the light source / detector interface.

[0120] This application introduces a reconfigurable multi-segment electro-optic modulation structure on a thin-film lithium niobate integrated chip. By segmenting the common ground electrode and the two signal electrodes (i.e., the first signal electrode and the second signal electrode), multiple effective electrode length combinations within a single modulator can be achieved. Without adding multiple modulators or multiple fiber optic gyroscopes, the reconfigurable switching of linear range and modulation sensitivity can be realized in the structure.

[0121] This application embodiment, by reasonably selecting the length relationship of the first modulation segment, the second modulation segment, and the third modulation segment, makes the first mode suitable for large angular velocity measurement, the third mode suitable for small angular velocity and high-precision creep measurement, and the second mode used in the medium angular velocity region. Thus, without changing the length of the polarization-maintaining fiber ring and the external light source, the dynamic range of the system is significantly expanded, while maintaining high resolution at small angular velocities.

[0122] This application embodiment integrates the first multimode interference coupler, the polarization rotating beam splitter, and the second multimode interference coupler onto the same thin-film lithium niobate chip, completing the beam splitting, combining, and polarization management between the light source and the detection port, and the polarization-maintaining fiber ring. This reduces discrete optical components and fiber connection points, lowers insertion loss and polarization-related errors, and helps improve system stability and environmental adaptability.

[0123] The embodiments of this application use two signal electrodes (i.e., the first signal electrode and the second signal electrode) to achieve multi-mode driving. Only a few driving channels are needed to obtain multiple levels of sensitivity and range. The driving structure is simple and easy to cooperate with the control circuit to achieve automatic mode switching. It reduces the difficulty and cost of overall packaging and is suitable for engineering applications on high dynamic and miniaturized platforms such as tactical missiles.

[0124] The multi-segment modulation structure and electrode configuration proposed in this application have good scalability. The number and length of modulation segments can be increased or adjusted according to application requirements to achieve more ranges or more precise range classifications, providing a general approach for the integrated design of subsequent multi-axis fiber optic gyroscopes and other electro-optic sensors.

[0125] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. The sequence numbers of the above-described embodiments are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0126] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another system, or some features may be ignored or not performed.

[0127] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A fiber optic gyroscope chip, characterized in that, Applications in fiber optic gyroscope systems; The fiber optic gyroscope chip includes at least: Integrated optical waveguide structure located in a thin-film lithium niobate layer; A multi-segment optoelectronic modulation structure is located in the cladding layer on the thin-film lithium niobate layer. The multi-segment optoelectronic modulation structure is arranged sequentially along the light propagation direction on the fiber optic gyroscope chip. Each optoelectronic modulation structure includes electrodes disposed on both sides of the integrated optical waveguide structure. Each of the photoelectric modulation structures is configured to be turned on or off under the drive of the control circuit of the fiber optic gyroscope system, resulting in multiple modulation structures with different effective electrode lengths and modulation modes corresponding to each modulation structure, so as to realize multi-level reconfigurable switching of the phase modulation sensitivity and linear range of the fiber optic gyroscope.

2. The fiber optic gyroscope chip according to claim 1, characterized in that, The integrated optical waveguide structure includes an optical waveguide core region, which is an asymmetric double-ridge waveguide. Each optoelectronic modulation structure includes at least one of a first modulation signal electrode connected to a first signal electrode and a second modulation signal electrode connected to a second signal electrode, and at least one modulation ground electrode connected to a common ground electrode. Each of the optical waveguide core regions is provided with one of the first modulation signal electrode and the second modulation signal electrode on both sides, as well as the modulation ground electrode; The common ground electrode, the first signal electrode, and the second signal electrode are electrically connected to the control circuit, and the first signal electrode and the second signal electrode are configured to be turned on or off under the drive of the control circuit.

3. The fiber optic gyroscope chip according to claim 2, characterized in that, The multi-segment optoelectronic modulation structure includes at least a first modulation segment, a second modulation segment, and a third modulation segment; the modulation mode includes at least a first mode, a second mode, and a third mode; The first modulation segment includes at least one first modulation signal electrode and at least one modulation ground electrode; The second modulation segment includes at least one second modulation signal electrode and at least one modulation ground electrode; The third modulation segment includes at least one second modulation signal electrode and at least one modulation ground electrode; When the first signal electrode is turned on and the second signal electrode is turned off, the first modulation segment is in the modulation working state, and the multi-segment photoelectric modulation structure is in the first mode; When the first signal electrode is off and the second signal electrode is on, the second modulation segment and the third modulation segment are in a modulation working state, and the multi-segment photoelectric modulation structure is in the second mode. When both the first signal electrode and the second signal electrode are turned on, the first modulation segment, the second modulation segment, and the third modulation segment are all in a modulation working state, and the multi-segment photoelectric modulation structure is in the third mode.

4. The fiber optic gyroscope chip according to claim 3, characterized in that, The first modulation segment has a first length, which is the sum of the electrode lengths in the first modulation segment where the first modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region in the optical propagation direction. The second modulation segment has a second length, which is the sum of the electrode lengths in the second modulation segment where the second modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region, respectively, in the direction of light propagation. The third modulation segment has a third length, which is the sum of the electrode lengths in the third modulation segment where the second modulation signal electrode and the modulation ground electrode interact with the optical waveguide core region, respectively, in the direction of light propagation. The effective electrode length of the first mode is the first length; The effective electrode length of the second mode is the sum of the second length and the third length; The effective electrode length of the third mode is the sum of the first length, the second length, and the third length; The effective electrode length of the third mode is greater than that of the second mode, and the effective electrode length of the second mode is greater than that of the first mode.

5. The fiber optic gyroscope chip according to any one of claims 1 to 4, characterized in that, The fiber optic gyroscope chip also includes an on-chip optical path function module; The integrated optical waveguide structure includes at least a first optical port, a second optical port, a third optical port, and a fourth optical port; the first optical port is connected to the light source of the fiber optic gyroscope, the second optical port is connected to the detector fiber of the fiber optic gyroscope, and the third and fourth optical ports are used to connect to the two ends of the polarization-maintaining fiber loop, respectively. The on-chip optical path functional module is disposed between the first optical port and the second optical port and the third optical port and the fourth optical port. The on-chip optical path functional module includes at least a first multimode interference coupler, a polarization rotation beam splitter and a second multimode interference coupler connected in sequence.

6. The fiber optic gyroscope chip according to claim 5, characterized in that, The first multimode interference coupler is configured to split the incident light from the light source into a power beam and input it into the polarization rotating beam splitter, and to combine the interference light returning from the polarization-maintaining fiber loop and couple it to the second optical port. The polarization rotating beam splitter is configured to rotate and polarize the optical signal. The second multimode interference coupler is configured to split the optical signal from the polarization rotating beam splitter and to perform interference combining of the optical signals returned from both ends of the polarization-maintaining fiber loop.

7. The fiber optic gyroscope chip according to any one of claims 1 to 4, characterized in that, The fiber optic gyroscope chip also includes: A substrate layer, wherein the thin-film lithium niobate layer is disposed on the substrate layer; Cladding, covering the integrated optical waveguide structure; A metal electrode layer, including at least the multi-segment photoelectric modulation structure, is disposed on the cladding layer.

8. A fiber optic gyroscope system, characterized in that, It includes at least the fiber optic gyroscope chip, light source, detector, polarization-maintaining fiber optic ring, and control circuit as described in any one of claims 1 to 7; The light source is connected to the first optical port in the fiber optic gyroscope chip via an optical fiber; The detector is connected to the second optical port in the fiber optic gyroscope chip via an optical fiber; The two ends of the polarization-maintaining fiber loop are respectively connected to the third optical port and the fourth optical port in the fiber optic gyroscope chip. The control circuit is electrically connected to the multiple photoelectric modulation structures in the fiber optic gyroscope chip to drive each photoelectric modulation structure to be turned on or off, thereby obtaining multiple modulation structures with different effective electrode lengths and modulation modes corresponding to each modulation structure. This enables multi-level reconfigurable switching of the fiber optic gyroscope's phase modulation sensitivity and linear range, and demodulates the signal output by the detector to obtain angular velocity information.

9. The fiber optic gyroscope system according to claim 8, characterized in that, The control circuit includes at least: The modulation driving unit is configured to generate a driving voltage signal or a driving current signal applied to each segment of the opto-modulation structure. The mode control unit is configured to select a modulation mode based on the current angular velocity information or the system operating state, and control the modulation drive unit to output a corresponding drive voltage signal or drive current signal based on the modulation mode. The analog front-end unit is configured to amplify and filter the analog signal output by the detector to obtain a processed signal; An analog-to-digital conversion unit is configured to perform analog-to-digital conversion on the processed signal to obtain a digital signal; The demodulation and data processing unit is configured to calculate the angular velocity information based on the digital signal.

10. The fiber optic gyroscope system according to claim 9, characterized in that, The control circuit pre-sets a first angular velocity threshold and a second angular velocity threshold, wherein the first angular velocity threshold is less than the second angular velocity threshold; the modulation mode includes at least a first mode, a second mode, and a third mode, each mode corresponding to a pre-calibrated scaling factor; The demodulation and data processing unit is further configured to demodulate the digital signal based on the current modulation mode of the fiber optic gyroscope chip to obtain demodulated data. The demodulation and data processing unit is further configured to convert the demodulated data based on the scaling factor corresponding to the current modulation mode to obtain the current angular velocity information; The mode control unit is further configured to adjust the modulation mode based on the current angular velocity information, the first angular velocity threshold, and the second angular velocity threshold.

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