A fast resetting and locking method for a resonant optical gyroscope

Abstract

The invention discloses a fast resetting and locking method for a resonant optical gyroscope, the method comprising: when the actual frequency tuning amount of a tunable laser exceeds a set frequency resetting threshold value [f min ,f max ], the gyro enters the frequency reset state, and the frequency tuning amount changes f1 in the opposite direction of exceeding the threshold, and then continues to change with f2 as the step size, until the laser output frequency enters another positive feedback zone within the set frequency reset threshold range, and then the frequency tuning amount performs proportional feedback according to the demodulated output, and after the laser output frequency approaches the resonant frequency of the resonant cavity, the reset is completed and the stable closed-loop state is re-entered. The present invention greatly reduces the reset time, so that the resonant optical gyroscope can work effectively for a long time, and avoids the problem of long reset time caused by the limited step response of the laser in the traditional step reset technology.

Description

Technical Field

[0001] The present application relates to the technical field of optical gyroscopes, and in particular to a rapid resetting and locking device and method for a resonant optical gyroscope. Background Art

[0002] The resonant optical gyroscope is an angular velocity sensor based on the Sagnac effect. It detects the difference in the resonant frequency in the forward and reverse directions of the optical resonant cavity to obtain the angular velocity of rotation. Compared with the interferometric optical gyroscope, the resonant optical gyroscope requires a much shorter resonant cavity ring length when meeting the same performance indicators, thus having greater potential for miniaturization and integration.

[0003] The working condition of a resonant optical gyroscope is that the laser frequency is within the half-maximum full width range near the resonant frequency of the resonant cavity. Due to the limited frequency stability of the laser and the great change in the resonant frequency with temperature, most resonant optical gyroscopes currently use a closed-loop feedback locking working scheme: the optical frequency of the tunable laser is locked to the resonant frequency in one direction of the resonant cavity. At this time, the difference between the optical frequency and the resonant frequency in the other direction of the resonant cavity is the difference between the resonant frequencies in the forward and reverse directions. In practice, when the feedback-locked tuning voltage floats out of the control circuit voltage range, the closed-loop feedback will be unlocked and the gyroscope will not work properly. On the other hand, the frequency response bandwidth of the tunable laser used in the resonant optical gyroscope is limited, so the laser frequency cannot be stably moved to near another resonant frequency that can be locked by simply applying a simple step signal.

[0004] In summary, when the resonant optical gyroscope works in a variable temperature environment for a long time, frequency lockout is inevitable. A fast and accurate reset method is helpful to improve the data validity of the resonant optical gyroscope. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a fast reset and locking method for a resonant optical gyroscope to overcome the limited response of a tunable laser to a step modulation signal, reduce the unlocking reset time of the resonant optical gyroscope, and reduce the measurement error caused by reset in a variable temperature environment.

[0006] According to an embodiment of the present application, a rapid reset and locking method for a resonant optical gyroscope is provided, characterized in that the resonant optical gyroscope comprises a tunable laser, a phase modulation module, a Sagnac effect generating optical path with an optical resonant cavity as the core, a photoelectric conversion module, a phase-locked amplification and demodulation module, a servo control module and a reset control module. The light emitted by the tunable laser is modulated by the phase modulation module and enters the Sagnac effect generating optical path with the optical resonant cavity as the core. The output light is converted into an electrical signal by the photoelectric conversion module and then demodulated by the phase-locked amplification and demodulation module. When the gyroscope is in a stable closed-loop state, the demodulation result enters the servo control module to generate a feedback voltage, which is applied to the frequency tuning end of the tunable laser. When the gyroscope is in a frequency reset state, the demodulation result is used as a judgment basis for the reset control module, and the reset control module outputs a feedback voltage which is applied to the frequency tuning end of the tunable laser.

[0007] The fast reset lockout method includes:

[0008] When the actual frequency tuning amount of the tunable laser is greater than the set frequency reset threshold f max When the gyro enters the frequency reset state, the frequency tuning amount is first reduced by f1, and then continuously reduced with f2 as the step size, until the laser output frequency enters the positive feedback area, the frequency tuning amount is proportionally fed back according to the demodulated output, and when the laser output frequency is close to the resonant frequency of the resonant cavity, the reset is completed and the stable closed-loop state is entered;

[0009] When the actual frequency tuning amount of the tunable laser is less than the set frequency reset threshold f min When the gyro enters the frequency reset state, the frequency tuning amount first increases by f1, and then increases continuously with f2 as the step size, until the laser output frequency enters the positive feedback area. The frequency tuning amount performs proportional feedback according to the demodulated output. When the laser output frequency is close to the resonant frequency of the resonant cavity, the reset is completed and the stable closed-loop state is entered.

[0010] When the actual frequency tuning amount of the tunable laser is within the set frequency reset threshold [f min ,f max ], the gyro is in a stable closed-loop state, and proportional-integral control is used to lock the laser output frequency to the resonant frequency of the resonant cavity.

[0011] Optionally, the set frequency reset threshold [f min ,f max ] is smaller than the frequency tuning range of a tunable laser and larger than a free spectral region of an optical resonant cavity.

[0012] Optionally, the change value f1 of the frequency tuning amount is greater than a free spectrum range of the optical resonant cavity, and f2 is less than 1 / 3 of the full width at half maximum of the optical resonant cavity.

[0013] Optionally, the positive feedback region refers to a frequency region centered on the resonant frequency of the resonant cavity, and the range is between 1 and 1.5 times the half-height full width of the resonant cavity.

[0014] Optionally, the determination condition for completing the resetting is that the laser frequency enters a range smaller than 1 / 10 of the half-maximum full width near the resonant frequency of the resonant cavity.

[0015] Optionally, the phase modulation module is composed of at least one signal generator and one phase modulator, and the phase modulation frequency generated by the signal generator is smaller than the half-width at half maximum of the optical resonant cavity.

[0016] Optionally, the Sagnac effect generating optical path with the optical resonant cavity as the core includes an optical beam splitter, two optical circulators (or optical couplers) and an optical resonant cavity. The light after phase modulation is divided into two paths and passes through the optical circulator (or optical coupler) respectively, and enters the optical resonant cavity in clockwise and counterclockwise directions respectively. The two paths of light transmitted from the optical resonant cavity then pass through another optical circulator (or optical coupler) respectively, and are finally output from the Sagnac effect generating optical path.

[0017] Optionally, the Sagnac effect generating optical path with the optical resonant cavity as the core is composed of optical fiber devices or integrated optical devices, and the structure of the optical resonant cavity is a transmission resonant cavity or a reflection resonant cavity.

[0018] Optionally, the phase-locked amplifier and demodulation module includes at least two phase-locked amplifiers, which demodulate the signals in the forward and reverse transmission light directions respectively, and the demodulation frequency is equal to the phase modulation frequency. One of the demodulation results in the forward and reverse directions is the gyroscope output, and the other demodulation result enters the servo control module or the reset control module.

[0019] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0020] As can be seen from the above embodiments, the present application does not increase the hardware burden of the resonant optical gyroscope system, and only adopts a segmented reset method in the software. At the beginning of the reset, the frequency tuning amount is changed in the direction opposite to the threshold by f1. Since the temperature change and the frequency drift of the laser itself are mostly in a unidirectional trend, this method can increase the distance between the frequency tuning amount after the reset is completed and the set frequency reset threshold, thereby reducing the frequency of the reset. Next, the laser output frequency continues to move linearly in a single direction, and while the continuous frequency shift is close to the resonance peak frequency of the resonant cavity, the problem of the limited response of the tunable laser to the step modulation signal is overcome. Secondly, after the optical frequency enters the positive feedback area, the proportional feedback can be used to increase the response speed and make the optical frequency quickly approach the resonant frequency. When the optical frequency approaches the resonant frequency and completes the reset, the proportional integral feedback can reduce the locking residual caused by the proportional feedback, and improve the locking accuracy and stability. In summary, the present invention can effectively reduce the reset frequency, overcome the problem of limited bandwidth of the tunable laser, shorten the reset time, and thus reduce the output error under the temperature change environment through the segmented reset method.

[0021] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] Figure 1 The figure is a schematic diagram of the structure of a resonant optical gyroscope according to an exemplary embodiment.

[0024] Figure 2 The present invention is a flow chart showing a method for fast resetting and locking a resonant optical gyroscope according to an exemplary embodiment.

[0025] Figure 3 The present invention is a schematic diagram showing parameter selection of a fast reset and locking method of a resonant optical gyroscope according to an exemplary embodiment. DETAILED DESCRIPTION

[0026] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0027] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0028] Figure 1 The present invention is a schematic diagram of the structure of a resonant optical gyroscope proposed in an example of the present invention, including a tunable laser, a phase modulation module, a Sagnac effect optical path with an optical resonant cavity as the core, a photoelectric conversion module, a phase-locked amplifier module, a servo control module and a reset control module. The light emitted by the tunable laser is modulated by the phase modulation module and enters the Sagnac effect optical path with the optical resonant cavity as the core. The output light is converted into an electrical signal by the photoelectric conversion module and then demodulated by the phase-locked amplifier module. When the gyroscope is in a stable closed-loop state, the demodulation result enters the servo control module to generate a feedback voltage, which is applied to the frequency tuning end of the tunable laser. When the gyroscope is in a frequency reset state, the demodulation result is used as a judgment basis for the reset control module, and the reset control module outputs a feedback voltage that is applied to the frequency tuning end of the tunable laser.

[0029] In this embodiment, the phase modulation module is composed of at least one signal generator and one phase modulator. The signal generator generates a modulation signal and applies it to both ends of the phase modulator to phase modulate the optical signal passing through the phase modulator. In conjunction with the phase-locked amplifier module, the signal-to-noise ratio of the system can be greatly improved. To ensure that the optical signal passing through the resonant cavity is not distorted, the phase modulation frequency generated by the signal generator should be less than the half-height full width of the optical resonant cavity.

[0030] In this embodiment, the Sagnac effect generating optical path with the optical resonant cavity as the core includes but is not limited to an optical beam splitter, two optical circulators (or optical couplers) and an optical resonant cavity. The light after phase modulation is divided into two paths and passes through the optical circulator (or optical coupler) respectively, and enters the optical resonant cavity in clockwise and counterclockwise directions respectively. The two paths of light transmitted from the optical resonant cavity pass through another optical circulator (or optical coupler) respectively, and finally output from the Sagnac effect generating optical path. The Sagnac effect generating optical path with the optical resonant cavity as the core is composed of optical fiber devices or integrated optical devices, and the structure of the optical resonant cavity is a transmission resonant cavity or a reflection resonant cavity.

[0031] In this embodiment, the phase-locked amplifier module includes at least two phase-locked amplifiers, which demodulate the signals in the forward and reverse directions of the transmitted light respectively, and the demodulation frequency is equal to the phase modulation frequency. One of the demodulation results in the forward and reverse directions is the gyro output, and the other demodulation result enters the servo control module or the reset control module. The output of the servo control module or the reset control module controls the frequency of the tunable laser, locks the output frequency of the laser to the resonant frequency of this path, and realizes closed-loop frequency locking.

[0032] Figure 2 This is a flow chart of a method for quickly resetting and locking a resonant optical gyroscope provided by an example of the present invention. The method comprises:

[0033] (1) When the actual frequency tuning amount of the tunable laser is greater than the set frequency reset threshold f max When the gyro enters the frequency reset state, the frequency tuning amount first decreases by f1, and then continues to decrease with a step size of f2 until the laser output frequency enters the positive feedback area. The frequency tuning amount performs proportional feedback according to the demodulated output. After the laser output frequency is close to the resonant frequency of the resonant cavity, the reset is completed and the stable closed-loop state is entered.

[0034] (1) When the actual frequency tuning amount of the tunable laser is less than the set frequency reset threshold f min When the gyro enters the frequency reset state, the frequency tuning amount first increases by f1, and then increases continuously with f2 as the step size until the laser output frequency enters the positive feedback area. The frequency tuning amount performs proportional feedback according to the demodulated output. After the laser output frequency is close to the resonant frequency of the resonant cavity, the reset is completed and the stable closed-loop state is entered.

[0035] (1) When the actual frequency tuning amount of the tunable laser is within the set frequency reset threshold [f min ,f max ], the gyro is in a stable closed-loop state, and proportional-integral control is used to lock the laser output frequency to the resonant frequency of the resonant cavity.

[0036] It can be seen from the above embodiments that the present application uses a segmented reset method to continuously shift the frequency of the laser to make it close to the resonant frequency of the resonant cavity, thereby overcoming the problem of limited response of the tunable laser bandwidth to step signals; when the laser frequency enters the positive feedback region, proportional feedback is used to effectively shorten the reset time; after re-entering the stable closed-loop state, proportional integral feedback is used to reduce the locking residual.

[0037] Figure 3This is a parameter selection diagram of a fast reset and locking method for a resonant optical gyroscope provided by an example of the present invention. Taking the drift of the resonant frequency to the left under environmental changes as an example, the frequency reset state process and parameter selection are demonstrated. In a stable closed-loop state, the feedback voltage applied to the laser frequency modulation port causes the optical frequency to be locked at the center of the demodulation curve. When temperature changes and the frequency drift of the laser itself cause the locking point to exceed the frequency tuning range, the gyroscope will lose lock. At this time, it is necessary to quickly readjust the feedback voltage to the center of other demodulation curves within the modulation voltage range to achieve reset lock. Therefore, the frequency reset threshold [f min ,f max ] is smaller than the frequency tuning range of the tunable laser and larger than a free spectrum area of ​​the optical resonant cavity, ensuring that the center of the next demodulation curve can be found after loss of lock. The frequency tuning change f1 should be slightly larger than the free spectrum area of ​​the optical resonant cavity, increasing the distance between the feedback voltage after the reset is completed and the set frequency reset threshold, thereby reducing the frequency of reset. The frequency tuning change f2 should be less than 1 / 3 of the half-height full width of the optical resonant cavity to avoid missing the positive feedback area due to excessive frequency changes. The positive feedback area refers to a frequency region centered on the resonant frequency of the resonant cavity, and its range is between 1 and 1.5 times the half-height full width of the resonant cavity. The judgment condition for completing the reset is that the laser frequency enters a range of less than 1 / 10 of the half-height full width near the resonant frequency of the resonant cavity.

[0038] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0039] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for quickly resetting and locking a resonant optical gyroscope, characterized in that: The resonant optical gyroscope comprises a tunable laser, a phase modulation module, a Sagnac effect generating optical path with an optical resonant cavity as the core, a photoelectric conversion module, a phase-locked amplifier and demodulation module, a servo control module and a reset control module. The light emitted by the tunable laser is modulated by the phase modulation module and enters the Sagnac effect generating optical path with the optical resonant cavity as the core. The output light is converted into an electrical signal by the photoelectric conversion module and then demodulated by the phase-locked amplifier and demodulation module. When the gyroscope is in a stable closed-loop state, the demodulation result enters the servo control module to generate a feedback voltage, which is applied to the frequency tuning end of the tunable laser. When the gyroscope is in a frequency reset state, the demodulation result is used as a judgment basis of the reset control module, and the reset control module outputs a feedback voltage which is applied to the frequency tuning end of the tunable laser. The fast reset lockout method includes: When the actual frequency tuning amount of the tunable laser is greater than the set frequency reset threshold f max When the gyro enters the frequency reset state, the frequency tuning amount decreases first. f 1, then f 2 is the step size that keeps decreasing until the laser output frequency enters the positive feedback region. The frequency tuning amount is proportionally fed back according to the demodulated output. When the laser output frequency approaches the resonant frequency of the resonant cavity, the reset is completed and the state of stable closed loop is entered. When the actual frequency tuning amount of the tunable laser is less than the set frequency reset threshold f min When the gyro enters the frequency reset state, the frequency tuning amount increases first. f 1, then f 2 is the step size that keeps increasing until the laser output frequency enters the positive feedback region. The frequency tuning amount is proportionally fed back according to the demodulated output. When the laser output frequency approaches the resonant frequency of the resonant cavity, the reset is completed and the state of stable closed loop is entered. When the actual frequency tuning amount of the tunable laser is within the set frequency reset threshold [ f min , f max ], the gyro is in a stable closed-loop state, and proportional-integral control is adopted to lock the laser output frequency to the resonant frequency of the resonant cavity; Wherein, the set frequency reset threshold [ f min , f max ] is smaller than the frequency tuning range of the tunable laser and larger than a free spectral region of the optical resonant cavity, and the change value of the frequency tuning amount is f 1 is larger than a free spectral range of an optical resonant cavity, f 2 is less than 1 / 3 of the full width at half maximum of the optical resonant cavity.

2. The rapid resetting and locking method of a resonant optical gyroscope according to claim 1, characterized in that: The positive feedback region refers to a frequency region centered on the resonant frequency of the resonant cavity, and its range is between 1 and 1.5 times the half-height full width of the resonant cavity.

3. The rapid resetting and locking method of a resonant optical gyroscope according to claim 1, characterized in that: The determination condition for completing the resetting is that the laser frequency enters a range smaller than 1 / 10 of the half-maximum full width near the resonant frequency of the resonant cavity.

4. The method for rapid resetting and locking of a resonant optical gyroscope according to claim 1, characterized in that: The phase modulation module is composed of at least one signal generator and one phase modulator, and the phase modulation frequency generated by the signal generator is smaller than the half-width at half maximum of the optical resonant cavity.

5. The method for rapid resetting and locking of a resonant optical gyroscope according to claim 1, characterized in that: The Sagnac effect generating optical path with the optical resonant cavity as the core includes an optical beam splitter, two optical circulators (or optical couplers) and an optical resonant cavity. The light after phase modulation is divided into two paths and passes through the optical circulator (or optical coupler) respectively, and enters the optical resonant cavity in clockwise and counterclockwise directions respectively. The two paths of light transmitted from the optical resonant cavity then pass through another optical circulator (or optical coupler) respectively, and are finally output from the Sagnac effect generating optical path.

6. The method for rapid resetting and locking of a resonant optical gyroscope according to claim 1, characterized in that: The Sagnac effect generating optical path with the optical resonant cavity as the core is composed of optical fiber devices or integrated optical devices, and the structure of the optical resonant cavity is a transmission resonant cavity or a reflection resonant cavity.

7. The method for rapid resetting and locking of a resonant optical gyroscope according to claim 1, characterized in that: The phase-locked amplifier and demodulation module includes at least two phase-locked amplifiers, which demodulate the signals in the forward and reverse directions of the transmitted light respectively. The demodulation frequency is equal to the phase modulation frequency. One of the demodulation results in the forward and reverse directions is the gyro output, and the other demodulation result enters the servo control module or the reset control module.

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