Loss-lock control-based large-variable-temperature resonant fiber-optic gyroscope and control method thereof

Abstract

The invention provides a large-variable-temperature resonant fiber-optic gyroscope based on lock loss control and a control method thereof.According to the fiber-optic gyroscope, a self-adaptive control link is introduced in the frequency tracking process, and a digital working area is divided into a current control area and a temperature control area according to different frequency control ranges; the high-precision advantage of current control and the large-range characteristic of temperature control are considered, and the method can be suitable for accurate and stable frequency control under the condition of large variable temperature, so that rapid, stable and real-time tracking synchronization of the center frequency of the laser to a single resonant frequency point of the optical fiber resonant cavity is realized; therefore, the problem of frequency lock losing of the resonant fiber-optic gyroscope is solved from the aspect of control, the zero position change in the frequency secondary locking process is also effectively avoided, and the precision of the gyroscope is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of optical sensing technology, and in particular to a large-temperature-varying resonant fiber optic gyroscope based on unlock control and its control method. Background Technology

[0002] With the widespread application of navigation and positioning systems and the rapid development of aerospace and aviation high technologies, high-precision, miniaturized optical gyroscope inertial devices have become an important research direction in my country's major science and technology programs. Resonant fiber optic gyroscopes have enormous application prospects in terms of high precision, miniaturization, and ultra-stability, and have become a cutting-edge research hotspot in next-generation inertial sensors. They use optical fibers several meters or tens of meters long to construct a stable resonant cavity as a frequency reference, and the rotational speed is determined by measuring the frequency deviation. Therefore, resonant fiber optic gyroscopes have high theoretical accuracy and significant advantages in terms of overall performance, including cost and size.

[0003] The operation of a resonant fiber optic gyroscope relies on the rapid and stable tracking of the laser frequency to the resonant frequency of the resonant cavity. However, traditional narrow-linewidth lasers exhibit significant temperature-center frequency drift, typically reaching GHz / ℃. The temperature-resonant frequency of the fiber optic resonant cavity is also usually as high as GHz / ℃. This asymmetry between the laser's center frequency and the resonant frequency drift prevents the center frequency from rapidly, stably, and in real-time tracking the resonant frequency; this problem is known as "lock-off." Specifically, the gyroscope output may show... Figure 6 As shown, rapid temperature changes cause the gyroscope output to be discontinuous, making it difficult to continuously detect the rotation speed. Therefore, traditional resonant fiber optic gyroscopes are mostly tested under stable laboratory conditions, which are difficult to adapt to engineering applications under conditions of large temperature variations in resonant frequency. Summary of the Invention

[0004] This invention provides a large-temperature-varying resonant fiber optic gyroscope based on unlock control and its control method, which can solve the technical problem that traditional resonant fiber optic gyroscopes are difficult to adapt to large-temperature-varying resonant frequencies.

[0005] According to one aspect of the present invention, a large-temperature resonant fiber optic gyroscope based on unlock control is provided, comprising an ultra-narrow linewidth laser, a first optical isolator, a polarizer, an optical modulator, a first coupler, a resonant cavity, a second coupler, a second optical isolator, a third optical isolator, a first detector, a second detector, a digital closed-loop control circuit, and a drive control circuit.

[0006] The laser emitted by the ultra-narrow linewidth laser passes sequentially through a first optical isolator and a polarizer before entering an optical modulator. The optical modulator modulates the received laser based on the modulation signal and the polarization signal, and splits the beam into two linearly polarized beams of equal power. Both beams are coupled into the resonant cavity through a first coupler, and propagate in clockwise and counterclockwise directions respectively within the resonant cavity. After propagating several times within the resonant cavity, the two linearly polarized beams enter a second coupler to form multi-beam interference. The counterclockwise linearly polarized beam passes through a second optical isolator and enters a first detector, where the first detector performs photoelectric conversion on the counterclockwise linearly polarized beam to obtain a counterclockwise electrical signal. The clockwise linearly polarized beam passes through a third optical isolator and enters a second detector, where the second detector performs photoelectric conversion on the clockwise linearly polarized beam to obtain a clockwise electrical signal.

[0007] The digital closed-loop control circuit receives counterclockwise and clockwise electrical signals; it determines whether the counterclockwise signal is within the resonance valley. If the counterclockwise signal is not within the resonance valley, it performs a linear scan of the temperature control section of the ultra-narrow linewidth laser until the counterclockwise signal enters the resonance valley. If the counterclockwise signal is within the resonance valley, it generates a mixed waveform and applies it to the phase modulator in the optical modulator. The mixed waveform includes a triangular wave signal with frequency f1 and amplitude V1 and a sawtooth wave signal with frequency f2 and amplitude V2. The triangular wave signal is used as the modulation signal, and the sawtooth wave signal is used as the frequency offset signal. Simultaneously, it demodulates the clockwise and counterclockwise electrical signals to obtain the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency. It then obtains the differential-mode division multiplexing of the frequency difference between the laser frequency and the clockwise resonant frequency and the frequency difference between the laser frequency and the counterclockwise resonant frequency. The system is used to determine the current / temperature control range based on the differential mode component. If the differential mode component is within the linear closed-loop range of the drive current, the drive current is obtained based on the differential mode component and output to the drive control circuit. The drive control circuit then controls the current of the ultra-narrow linewidth laser until the center frequency of the ultra-narrow linewidth laser tracks the common mode component. If the differential mode component is within the temperature closed-loop range, the temperature is up-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. If the differential mode component is within the temperature upper closed-loop range, the temperature is down-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. The system is also used to output the common mode component as data from a resonant fiber optic gyroscope.

[0008] Preferably, the single-sided frequency shift generated by the triangular wave signal is equal to 1 / (2×3) of the full width at half maximum (FWHM) of the resonant cavity. 1 / 2 ).

[0009] Preferably, the amplitude V2 of the sawtooth wave signal is equal to the full-wave voltage of the optical modulator.

[0010] Preferably, the frequency tuning range corresponding to the linear closed-loop interval of the drive current is -0.25 to 0.25 GHz, the frequency tuning range corresponding to the closed-loop interval under temperature is -80 to -0.25 GHz, and the frequency tuning range corresponding to the closed-loop interval under temperature is 0.25 to 80 GHz, wherein the temperature-frequency tuning ratio is 1 GHz / ℃.

[0011] According to another aspect of the present invention, a control method for a large variable-temperature resonant fiber optic gyroscope based on unlock control is provided, the method performing unlock control on any of the above-mentioned large variable-temperature resonant fiber optic gyroscopes, the method comprising:

[0012] The digital closed-loop control circuit receives counterclockwise and clockwise electrical signals;

[0013] The digital closed-loop control circuit determines whether the counterclockwise electrical signal is within the resonance valley. If the counterclockwise electrical signal is not within the resonance valley, the temperature control section of the ultra-narrow linewidth laser is linearly scanned until the counterclockwise electrical signal enters the resonance valley. If the counterclockwise electrical signal is within the resonance valley, a mixed waveform is generated and applied to the phase modulator in the optical modulator. The mixed waveform includes a triangular wave signal with frequency f1 and amplitude V1 and a sawtooth wave signal with frequency f2 and amplitude V2. The triangular wave signal is used as the modulation signal, and the sawtooth wave signal is used as the frequency offset signal. At the same time, the clockwise and counterclockwise electrical signals are demodulated to obtain the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency.

[0014] The digital closed-loop control circuit acquires the differential-mode component and common-mode component of the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency.

[0015] The digital closed-loop control circuit determines the current / temperature control range based on the differential mode component. If the differential mode component is within the linear closed-loop range of the drive current, the drive current is obtained based on the differential mode component and output to the drive control circuit. The drive control circuit then controls the current of the ultra-narrow linewidth laser until the center frequency of the ultra-narrow linewidth laser tracks the common mode component. If the differential mode component is within the temperature closed-loop range, the temperature is up-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. If the differential mode component is within the temperature upper closed-loop range, the temperature is down-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current.

[0016] The digital closed-loop control circuit uses the common-mode component as the data output of the resonant fiber optic gyroscope.

[0017] By applying the technical solution of this invention, an adaptive control loop is introduced during the frequency tracking process. The digital working area is divided into a current control area and a temperature control area according to the different frequency control ranges. This takes into account the high precision advantage of current control and the wide range of temperature control, and can be applied to precise and stable frequency control under large temperature variation conditions. This enables rapid, stable, and real-time tracking and synchronization of the laser center frequency with a single resonant frequency point of the fiber optic resonant cavity. This solves the frequency "loosening" problem of resonant fiber optic gyroscopes from the control perspective and effectively avoids zero-position changes during the secondary frequency locking process, resulting in a significant improvement in gyroscope accuracy. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0019] Figure 1 A schematic diagram of a high-temperature resonant fiber optic gyroscope based on unlock control according to an embodiment of the present invention is shown.

[0020] Figure 2 A diagram of a lockout control scheme in a digital closed-loop control circuit according to an embodiment of the present invention is shown.

[0021] Figure 3 This diagram illustrates the partitioning of the FPGA digital working area in a lockout control scheme according to an embodiment of the present invention.

[0022] Figure 4 A block diagram of a common-mode frequency locking program according to an embodiment of the present invention is shown;

[0023] Figure 5 The gyroscope output after "loosening" control is shown in one embodiment of the present invention;

[0024] Figure 6 The output of a conventional resonant fiber optic gyroscope in a "loose" state is shown. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0028] like Figure 1 As shown, the present invention provides a large-temperature resonant fiber optic gyroscope based on unlock control, including an ultra-narrow linewidth laser, a first optical isolator, a polarizer, an optical modulator, a first coupler, a resonant cavity, a second coupler, a second optical isolator, a third optical isolator, a first detector, a second detector, a digital closed-loop control circuit, and a drive control circuit.

[0029] The laser emitted by the ultra-narrow linewidth laser passes sequentially through a first optical isolator and a polarizer before entering an optical modulator. The optical modulator modulates the received laser based on a modulation signal and a polarization signal, and then splits the beam to form two linearly polarized beams of equal power. The optical modulator includes a phase modulator and a Y-branch. The phase modulator modulates the received laser based on the modulation signal and the polarization signal, while the Y-branch splits the beam to form two linearly polarized beams of equal power. Both beams are coupled into a resonant cavity through a first coupler, and then propagate clockwise and counterclockwise, respectively, within the resonant cavity. After propagating several times within the resonant cavity, the two beams enter a second coupler to form multi-beam interference. The counterclockwise linearly polarized beam passes through a second optical isolator and enters a first detector, which performs photoelectric conversion on the counterclockwise linearly polarized beam to obtain a counterclockwise electrical signal. The clockwise linearly polarized beam passes through a third optical isolator and enters a second detector, which performs photoelectric conversion on the clockwise linearly polarized beam to obtain a clockwise electrical signal.

[0030] The digital closed-loop control circuit receives counterclockwise and clockwise electrical signals; it determines whether the counterclockwise signal is within the resonance valley. If the counterclockwise signal is not within the resonance valley, it performs a linear scan of the temperature control section of the ultra-narrow linewidth laser until the counterclockwise signal enters the resonance valley. If the counterclockwise signal is within the resonance valley, it generates a mixed waveform and applies it to the phase modulator in the optical modulator. The mixed waveform includes a triangular wave signal with frequency f1 and amplitude V1 and a sawtooth wave signal with frequency f2 and amplitude V2. The triangular wave signal is used as the modulation signal, and the sawtooth wave signal is used as the frequency offset signal. Simultaneously, it demodulates the clockwise and counterclockwise electrical signals to obtain the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency. It acquires the differential-mode component and common-mode component of the frequency difference between the laser frequency and the clockwise resonant frequency, and also uses it for... The differential-mode component is used to determine the current / temperature control range. If the differential-mode component is within the linear closed-loop range of the drive current, the drive current is obtained based on the differential-mode component and output to the drive control circuit. The drive control circuit then controls the current of the ultra-narrow linewidth laser until the center frequency of the ultra-narrow linewidth laser tracks the common-mode component (i.e., the center frequency of the ultra-narrow linewidth laser equals the common-mode component). If the differential-mode component is within the temperature closed-loop range, the temperature is up-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential-mode component enters the linear closed-loop range of the drive current. If the differential-mode component is within the temperature upper closed-loop range, the temperature is down-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential-mode component enters the linear closed-loop range of the drive current. The common-mode component is also used as the data output of the resonant fiber optic gyroscope.

[0031] To gain a further understanding of the present invention, the following description is provided. Figures 1-6 The present invention provides a detailed description of the variable-temperature resonant fiber optic gyroscope based on unlock control and its control method.

[0032] like Figure 1 As shown, this is a high-temperature-varying resonant fiber optic gyroscope. Laser light emitted from an ultra-narrow linewidth laser is transmitted unidirectionally via a first optical isolator. After polarization by a polarizer, it enters an optical modulator, where it is split into two linearly polarized beams of equal power. These beams are then coupled into the resonant cavity via a first coupler 1, where they propagate clockwise and counterclockwise, respectively. After beams with different numbers of revolutions exit the resonant cavity, they form multi-beam interference at the two exit ports of a second coupler 2. After passing through two optical isolators (ISO), they reach the first detector 1 and the second detector 2, respectively, where the light intensity signals are converted into electrical signals and input into a digital closed-loop control circuit. Based on the clockwise optical path electrical signal, the drive current and temperature of the laser are controlled by the drive control circuit to achieve synchronous locking of the laser's output light frequency to the clockwise optical path resonant frequency. The counterclockwise optical path electrical signal, after circuit signal processing, is output as an angular velocity through a port.

[0033] like Figure 2 As shown, in the digital closed-loop control circuit, a hybrid waveform signal modulation scheme of "triangular wave + sawtooth wave" is adopted to suppress backscattering noise in the resonant fiber optic gyroscope and improve the gyroscope signal-to-noise ratio. The hybrid waveform consists of a triangular wave signal with frequencies f1 and f2, and amplitudes V1 and V2, respectively, as the modulation signal and the bias signal. The triangular wave frequency f1 and amplitude V1 are determined by the sensitivity of the resonant fiber optic gyroscope, specifically by the full width at half maximum (FWHM) of the fiber optic resonant cavity, so that the single-sided frequency shift generated by the triangular wave is exactly equal to 1 / (2×3) of the full WHM of the resonant cavity. 1 / 2 At this point, the resonant fiber optic gyroscope has the highest sensitivity determined by the resonant cavity; the amplitude V2 of the sawtooth wave signal is equal to the full-wave voltage of the optical modulator, and the sawtooth wave frequency f2 is determined by the backscatter noise suppression effect. In actual operation, different backscatter noise suppression is achieved by adjusting the sawtooth wave frequency f2. By comparing the zero-bias stability of the gyroscope output, the minimum value is obtained to achieve the best backscatter noise suppression effect. The mixed waveform is specifically achieved through a sawtooth wave signal DAC and a triangular wave signal DAC. Depending on the accuracy of the mixed waveform signal, the bit depth of the two DACs is set to 12-16 bits, and the conversion rate is set to above 20MHz.

[0034] A "differential mode control, common mode output" signal detection scheme is adopted. Based on the differential mode components of the clockwise and counterclockwise demodulated signals, the differential mode components are used as the current and temperature control outputs of the ultra-narrow linewidth laser through interval determination. The center frequency of the ultra-narrow linewidth laser is stably controlled to the resonant frequency of the resonant cavity through the current control DAC and the temperature control DAC, respectively. The current control adopts a 16-bit, 100MHz slew rate high-precision, high-speed DAC to give full play to the high-precision tuning advantage of current-frequency; the temperature control adopts a 24-bit, 100kHz slew rate high-resolution, low-speed DAC to give full play to the wide-range tuning advantage of temperature-frequency.

[0035] like Figure 3 The diagram shows the FPGA digital operating range partitioning in the unlock control scheme. The 62536 and 3000 digital values ​​are set as the upper and lower operating extreme points, respectively. The range of 3000 to 62536 digital values ​​is defined as the linear closed-loop range of the drive current. Based on the control range of the current-controlled DAC and its minimum control value, the corresponding frequency tuning range is approximately -250 to 250 MHz. The control accuracy corresponding to the minimum bit is 500 MHz / (62536 - 3000) = 8.4 kHz / bit. In practice, the output rate is also taken into account, and this is achieved through multiple averaging of the output... This significantly improves current control accuracy to the order of several Hz to tens of Hz. By setting 0–3000 digital values ​​as the closed-loop range under temperature and 62536–65536 digital values ​​as the closed-loop range above temperature, and combining this with the DAC bit depth and voltage-temperature tuning coefficients, the frequency tuning ranges for the temperature-controlled DAC can be obtained as approximately -80 to -0.25 GHz and 0.25 to 80 GHz, respectively. Based on a temperature-frequency tuning ratio of approximately 1 GHz / ℃, this temperature control scheme can achieve a temperature tuning range of ±80℃, covering most engineering applications. Through precise subdivision of the current and temperature tuning ranges, it comprehensively utilizes the high precision and fast response frequency tuning characteristics of the drive current, as well as the wide tuning range of the die temperature.

[0036] like Figure 4 The diagram shown is a common-mode frequency locking (CML) program flowchart. Based on the common-mode components of the clockwise and counterclockwise demodulated signals, it directly outputs the gyroscope through an RS422 interface circuit. The specific steps include the following:

[0037] S1: Signal detection circuit is powered on;

[0038] S2: The digital closed-loop control circuit first determines whether the reset signal has arrived. If it has, the program is initialized and the register data in demodulation modules 1 and 2 is cleared. If it has not arrived, the next step is continued.

[0039] S3: Based on the counterclockwise electrical signal valley entry judgment, determine whether it has entered the resonance valley. If not, the temperature control DAC performs temperature scanning until it enters the resonance valley. If it does, continue to the next step.

[0040] S4: The mixed waveforms are generated by triangular wave signals and sawtooth wave signals with frequencies of f1 and f2 and amplitudes of V1 and V2, respectively, which are used as the modulation signal and the frequency offset signal.

[0041] S5: At this time, detector 1 and detector 2 output clockwise and counterclockwise signals respectively (e.g., Figure 2 (as shown in the image);

[0042] S6: Demodulate the clockwise and counterclockwise signals respectively to obtain the frequency difference f between the laser frequency and the clockwise resonant frequency. cw The frequency difference f between the laser frequency and the counterclockwise resonant frequency ccw The demodulated values ​​are stored in the registers of demodulation module 1 and demodulation module 2, respectively.

[0043] S7: Use f cw -f ccw The differential-mode component is used as the input for the current / temperature control range: if it is determined to be within the linear closed-loop range of the drive current, based on f... cw -f ccw The differential-mode component is used to obtain the drive current, and then the start-up current controls the DAC (digital-to-analog converter) to control the drive current of the existing laser until the laser center frequency is aligned with f. cw +f ccw For common-mode component tracking, if it is determined to be within the temperature-controlled closed-loop range or the temperature-controlled closed-loop range, the temperature control DAC is activated to control the laser temperature for wide-range tuning. Simultaneously, it determines whether the laser has entered the linear closed-loop range of the drive current, until the laser center frequency is aligned with f. cw +f ccw Common-mode tracking, typical gyroscope output under varying temperature conditions, such as Figure 5 As shown, the rapid temperature change has a significantly reduced impact on the gyroscope output, and no adverse effects have been observed. Figure 6 The discontinuous output problem shown;

[0044] S8: In f cw -f ccw In the process of determining the differential mode component, f is used. cw +f ccw The common-mode component is used as the data output of the resonant fiber optic gyroscope.

[0045] In summary, this invention provides a large-temperature-varying resonant fiber optic gyroscope and its control method based on unlock control. By introducing an adaptive control loop during frequency tracking, the digital operating area is divided into a current control area and a temperature control area according to the different frequency control ranges. This approach combines the high precision advantage of current control with the wide range characteristics of temperature control, enabling precise and stable frequency control under large temperature variations. This allows for rapid, stable, and real-time tracking and synchronization of the laser center frequency with a single resonant frequency point of the fiber optic resonator, thus solving the frequency "unlocking" problem of resonant fiber optic gyroscopes from a control perspective. It also effectively avoids zero-position changes during the secondary frequency locking process, resulting in a significant improvement in gyroscope accuracy.

[0046] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0047] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A large-temperature-varying resonant fiber optic gyroscope based on unlock control, characterized in that, It includes an ultra-narrow linewidth laser, a first optical isolator, a polarizer, an optical modulator, a first coupler, a resonant cavity, a second coupler, a second optical isolator, a third optical isolator, a first detector, a second detector, a digital closed-loop control circuit, and a drive control circuit. The laser emitted by the ultra-narrow linewidth laser passes sequentially through a first optical isolator and a polarizer before entering an optical modulator. The optical modulator modulates the received laser based on the modulation signal and the polarization signal, and splits the beam into two linearly polarized beams of equal power. Both beams of equal power are coupled into the resonant cavity through a first coupler and propagate in clockwise and counterclockwise directions, respectively, within the resonant cavity. After propagating several times within the resonant cavity, the two linearly polarized beams enter a second coupler to form multi-beam interference. The counterclockwise linearly polarized beam passes through a second optical isolator and enters a first detector. The first detector performs photoelectric conversion on the counterclockwise linearly polarized beam to obtain a counterclockwise electrical signal. The clockwise linearly polarized light enters the second detector through the third optical isolator. The second detector performs photoelectric conversion on the clockwise linearly polarized light to obtain a clockwise electrical signal. The digital closed-loop control circuit receives counterclockwise and clockwise electrical signals; it determines whether the counterclockwise signal is within the resonance valley. If the counterclockwise signal is not within the resonance valley, it performs a linear scan of the temperature control section of the ultra-narrow linewidth laser until the counterclockwise signal enters the resonance valley. If the counterclockwise signal is within the resonance valley, it generates a mixed waveform and applies it to the phase modulator in the optical modulator. The mixed waveform includes a triangular wave signal with frequency f1 and amplitude V1 and a sawtooth wave signal with frequency f2 and amplitude V2. The triangular wave signal is used as the modulation signal, and the sawtooth wave signal is used as the frequency offset signal. Simultaneously, it controls the clockwise and counterclockwise electrical signals... The electrical signal is demodulated to obtain the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency. The differential-mode component and common-mode component of the frequency difference between the laser frequency and the clockwise resonant frequency and the counterclockwise resonant frequency are obtained. It is also used to determine the current / temperature control range based on the differential-mode component. If the differential-mode component is within the linear closed-loop range of the drive current, the drive current is obtained based on the differential-mode component and output to the drive control circuit. The drive control circuit performs current control on the ultra-narrow linewidth laser until the center frequency of the ultra-narrow linewidth laser is tracked by the common-mode component. If the differential mode component is within the closed-loop temperature range, the temperature is tuned up and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. If the differential mode component is within the upper closed-loop temperature range, the temperature is down-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. It is also used to output the common-mode component as the data output of the resonant fiber optic gyroscope.

2. The fiber optic gyroscope according to claim 1, characterized in that, The single-sided frequency shift generated by the triangular wave signal is equal to 1 / (2×3) of the full width at half maximum (FWHM) of the resonant cavity. 1 / 2 ).

3. The fiber optic gyroscope according to claim 1 or 2, characterized in that, The amplitude V2 of the sawtooth wave signal is equal to the full-wave voltage of the optical modulator.

4. The fiber optic gyroscope according to any one of claims 1-3, characterized in that, The frequency tuning range corresponding to the linear closed-loop interval of the drive current is -0.25 to 0.25 GHz, the frequency tuning range corresponding to the closed-loop interval under temperature is -80 to -0.25 GHz, and the frequency tuning range corresponding to the closed-loop interval under temperature is 0.25 to 80 GHz. The temperature-frequency tuning ratio is 1 GHz / ℃.

5. A control method for a large-temperature-varying resonant fiber optic gyroscope based on unlock control, characterized in that, The method describes the loss-lock control of any of the large temperature-varying resonant fiber optic gyroscopes described in claims 1-4, and the method includes: The digital closed-loop control circuit receives counterclockwise and clockwise electrical signals; The digital closed-loop control circuit determines whether the counterclockwise electrical signal is within the resonance valley. If the counterclockwise electrical signal is not within the resonance valley, the temperature control section of the ultra-narrow linewidth laser is linearly scanned until the counterclockwise electrical signal enters the resonance valley. If the counterclockwise electrical signal is within the resonance valley, a mixed waveform is generated and applied to the phase modulator in the optical modulator. The mixed waveform includes a triangular wave signal with frequency f1 and amplitude V1 and a sawtooth wave signal with frequency f2 and amplitude V2. The triangular wave signal is used as the modulation signal, and the sawtooth wave signal is used as the frequency offset signal. At the same time, the clockwise and counterclockwise electrical signals are demodulated to obtain the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency. The digital closed-loop control circuit acquires the differential-mode component and common-mode component of the frequency difference between the laser frequency and the clockwise resonant frequency, and the frequency difference between the laser frequency and the counterclockwise resonant frequency. The digital closed-loop control circuit determines the current / temperature control range based on the differential mode component. If the differential mode component is within the linear closed-loop range of the drive current, the drive current is obtained based on the differential mode component and output to the drive control circuit. The drive control circuit then controls the current of the ultra-narrow linewidth laser until the center frequency of the ultra-narrow linewidth laser tracks the common mode component. If the differential mode component is within the temperature closed-loop range, the temperature is up-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. If the differential mode component is within the temperature upper closed-loop range, the temperature is down-tuned and output to the drive control circuit. The drive control circuit then controls the temperature of the ultra-narrow linewidth laser until the differential mode component enters the linear closed-loop range of the drive current. The digital closed-loop control circuit uses the common-mode component as the data output of the resonant fiber optic gyroscope.

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