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In order to optimize the detection accuracy and output stability of Resonant Integrated Optic Gyroscopes (RIOG), a dual closed-loop control method for combined differential modulation (DCM Control) has been proposed. Two optical signals are differentially modulated in sync, and their differential-mode output results are compensated in real-time. Considering the distinct characteristics of the two frequency servo loops, they are respectively utilized to tune the laser frequency to track the resonant frequency's wide fluctuations and continuously changing resonant frequency due to random rotation. Through this novel structure, we have enhanced reciprocity while reducing optical components, suppressing RIM noise and laser frequency noise in the gyroscope system, and effectively reducing control errors. We analyze the principles affecting angular velocity detection accuracy and the system's output model. Experimental results indicate that this method can effectively achieve high reciprocity and high-precision frequency control, offering a larger dynamic detection range and better linearity. The long-term bias instability (BI) based on Allan deviation is measured at 0.95°/h, and the angle random walk (ARW) is 0.119°/√h, providing a simple and efficient approach for RIOG closed-loop signal processing. [ABSTRACT FROM AUTHOR]

Backscatter noise is a key limiting factor in the performance of resonant fiber optic gyroscopes. To enhance the accuracy of resonant fiber optic gyroscopes, a gyroscope system based on sideband locking technology is proposed. In this scheme, two tunable semiconductor lasers independently provide the clockwise and counterclockwise optical paths. An optical phase-locked loop is employed to achieve independent subharmonic phase locking of the two output lights, with their optical frequency difference equaling one free spectral range (FSR). By applying sinusoidal modulation at different frequencies to generate sidebands, the sideband locking technique is used to lock the first-order sidebands of the two lights to adjacent resonant frequencies. Through the filtering effect of the fiber ring resonator, the carrier intensity of the transmitted light and other sidebands are effectively suppressed. With this signal processing technique, the influence of two types of backscatter noise is completely eliminated, and the additional suppression of laser frequency noise is achieved. Experimental results show that, based on the Allan deviation, the bias instability of the gyroscope output is 1.42°/h. This method significantly improves the detection accuracy of the resonant fiber optic gyroscope under the same parameter precision or device performance requirements. [ABSTRACT FROM AUTHOR]

For indoor close-range high-accuracy attitude measurement using inertial and vision sensors, the major challenge is to achieve a reliable attitude in various scenarios, specifically in the absence of vision information. To address this challenge, we present a fusion strategy for reliable attitude measurement using a micro electro mechanical system (MEMS) gyroscope and camera, particularly during discontinuous vision observations. The proposed algorithm consecutively executes update and prediction modes. In the update mode, when both inertial and visual data are available, the complete Kalman Filter (KF) conducts the entire filtering process and updates residual and state errors. In the absence of visual data, the partial KF operates only when the time update and filtering state vectors are compensated by the transfer residual, which is estimated through self-propagating state error. The parameters of least-squares support vector machine (LSSVM-NARX) continuously update until the next discontinuous vision observation occurs, with the desired outputs and inner inputs being the error angles and the exogenous inputs being the gyroscope values and time. In the prediction mode, without visual data, LSSVM-NARX can provide estimated angle errors between the complete and partial KFs, which are used to eliminate errors from partial KF output vectors to obtain a reliable and accurate attitude solution. Comparisons and extensive semi-physical simulation experiments under various motion trajectories were performed to validate the effectiveness and superiority of the proposed scheme in an accurate and reliable attitude measurement capability associated with discontinuous observations. [ABSTRACT FROM AUTHOR]

In the development of miniaturized optical gyroscopes, the resonant micro-optical gyroscope (RMOG) is the most representative sensor of new optical gyroscopes. However, in the manufacturing process of optical elements, the influence of backscattering and optical Kerr noise limits the performance of RMOG. A method of suppressing optical Kerr noise generated by the front end by compensating the optical power difference while suppressing the backscattering noise is introduced. In this method, we study the optimal strategy of double-phase modulation frequency to obtain the maximum spectral gap of clockwise and counterclockwise light, so as to suppress the error related to backscattered light. At the same time, the influence of Kerr noise on the optical path is reduced through the high-precision feedback loop of the intensity modulator. Based on Allan variance, the long-term deviation stability of RMOG reaches 0.98 deg/h. [ABSTRACT FROM AUTHOR]

For resonant micro-optical gyroscope (R-MOG), backscattering noise and optical Kerr noise are the main noises that affect the output accuracy of the gyroscope, and it is difficult to suppress them completely. This paper introduces a method to suppress the optical Kerr noise generated by the front end by compensating the optical power difference while suppressing the backscattered noise. Based on a single light source, the system changes the frequency difference between clockwise and counterclockwise optical paths through double-phase modulation, so as to improve the carrier rejection ratio and suppress the backscattered noise. At the same time, a high-speed feedback loop based on intensity modulator is designed, which is added to the optical loop to enhance the optical power, so as to reduce the impact of optical Kerr noise. The experimental results show that this method effectively suppresses the backscattered noise and optical Kerr noise, improves the output accuracy of the gyro by two orders of magnitude, and finally observes the long-term bias stability of 0.982°/h. [ABSTRACT FROM AUTHOR]

• The mechanism of nonreciprocal errors under the magnetic field-variable temperature field is proposed. • Based on dual-polarization interferometric fiber optic gyroscope (IFOG). • The nonreciprocal errors under the magnetic field, variable temperature field and magnetic field-variable temperature field are compared. A dual-polarization fiber optic gyroscope system is built to systematically analyze the nonreciprocal errors of the system under the magnetic field-variable temperature field. Under the magnetic field-variable temperature field, the nonreciprocal errors are caused by magnetic-thermal coupling birefringence nonreciprocal error, linear birefringence nonreciprocal error and Shupe effect error. The nonreciprocal errors of dual-polarization fiber optic gyroscope system are related to temperature and temperature gradient. In X and Y polarization states, the signs of magnetic-thermal coupling birefringence nonreciprocal error and linear birefringence nonreciprocal error are opposite, and these two errors can be suppressed in the dual-polarization system. But the Shupe effect errors are the same in X and Y polarization states, which can not be suppressed in the dual-polarization system. The experimental results are consistent with the theoretical analysis, which verifies the correctness of the nonreciprocal error model under the magnetic field-variable temperature field. The research results provide a theoretical and experimental basis for the study of the environmental adaptability of the fiber optic gyroscope and other common-path fiber sensing systems based on dual-polarization. [ABSTRACT FROM AUTHOR]

A self-injection locking method for resonant micro-optical gyroscope (RMOG) is proposed. The resonator is used as the sensitive element of the gyroscope and the device of light compression locking. The fiber and waveguide ring resonator (WRR) are designed and fabricated, consecutively. Both of the resonators can narrow the linewidth by three orders of magnitude, and the phase noise and the relative intensity noise can be reduced to −120 and −150 dBc / Hz, respectively. By evaluating the locking effect, WRR is more suitable for optical locking of a resonant micro-optical gyroscope (RMOG) light source, and its theoretical locking accuracy can reach 6.02 deg/s. [ABSTRACT FROM AUTHOR]