Research On Signal Detection Technology Of Circular Polarization Cavity Resonant Fiber-Optic Gyroscope

Resonant fiber optic gyroscope(RFOG)is a kind of optical gyroscope based on the optical Sagnac effect.Compared with the traditional interferometric fiber gyroscope,the resonant fiber gyroscope can achieve the same detection accuracy as the interferometric fiber gyroscope under the condition of shorter fiber ring,which has been widely concerned by researchers at home and abroad.Some scholars have demonstrated that using circular polarized cavity instead of traditional linear polarized cavity has a better effect on the suppression of various optical noises.On this basis,a new closed-loop control scheme is proposed by using the optical rotation effect of Faraday,and the related research work is carried out.The signal processing scheme proposed in this paper further enhances the reciprocity of the two signal processing channels of the resonator gyro,which is beneficial to the improvement of the gyro precision,expands the dynamic range and linearity,and overcomes the problem of the inevitable introduction of reset noise in the traditional signal processing scheme.In this paper,based on FPGA platform,the gyro signal detection system is designed and realized.The double closed-loop control of gyro is realized by the laser tuning and the optical rotation effect of Faraday coil as the control means.Specifically,this paper mainly carries out the following research work:First of all,this paper describes the whole scheme and principle of using Faraday optical rotation effect for closed loop,on this basis,the specific module composition and detection process of laser frequency servo loop and Faraday optical loop control loop are defined.Secondly,this paper designs and implements the laser frequency servo loop.The influence of sine wave modulation parameters on the demodulation curve is analyzed,and the sinusoidal signal generating module is designed and implemented.The influence of reference delay on the demodulation curve is analyzed,the first harmonic is extracted by locking amplifier,and the design and implementation of the signal demodulation module are realized.According to the characteristics of the servo loop,the mathematical model of the servo loop is established,and the frequency control module of the laser is designed and realized,and the control parameters are optimized.Then,the second compensation control is implemented by using the optical rotation characteristics of Faraday coil.The coil structure is designed and the magnetic field intensity generated by it is analyzed by finite element method.The relationship between the magnetic field and the incoming current and the magnetic field line integral inside the solenoid are obtained.The influence of the magnetic field intensity on the final result is deduced through theoretical calculation,and the relationship between the incoming current and the equivalent angular velocity is also deduced.The control method of Faraday rotating ray coil is designed,and the compensation module of the second circuit is realized.A nonlinear correction method is designed for nonlinear errors in the system.Finally,combined with the Faraday ray coil,based on FPGA as the core,the system is built,the test system is completed and the data acquisition is carried out.The results show that under the test time of 3600 s,the zero-offset stability of the resonator gyro using the common double closed-loop control scheme is 33.1deg/h,while the zero-offset stability of the resonator gyro using the control method described in this paper is 3.0deg/h,which is increased by 11 times.