Research Of The Nonideal Characteristics Of Laser Source And Resonator In Resonator Optic Gyroscope

Gyroscope is the basic sensor to detect the inertial angular velocity in the Navigation and guidance system. The resonator optic gyro (ROG) based on Sagnac effect is an important technological approach to achieve miniaturization and integration of high performance gyroscope. Compared with Interferometric Fiber Optic Gyro (IFOG), ROG has smaller volume and has the potential of integrated in a single chip. Compared with MEMS gyroscope, ROG is resistant to vibration and has better accuracy and stability.Highly coherent laser source and the optical resonance cavity are very critical components in a ROG. This paper conduct theoretical and experimental research on how these two key component affect the ROG performance. The main or innovational work of this thesis including:(1) The intermodulation noise in the ROG system is proposed and deeply analyzed. The intermodulation noise is produced by the laser frequency noise at the even multiples of the modulation frequency due to an intermodulation effect, this error will seriously limit the random noise performance of the resonator optic gyroscope. A systematic theoreitcal analysis of the intermodulation noise is conducted with different modulation index, system parameter, resonance cavity and laser source. When a modulation index of2.405is used to suppress the Rayleigh baskscattering noise, the intermodulation noise induced by a100kHz white noise linewidth laser source in a RFOG(resonator fiber optic gyro) system is in the10-3rad/s order, which is4orders of magnitude higher than the shot noise limit.(2) The intermodulation noise amplitude are measured by applying sin signal and white noise signal on a phase modulator to simulate the laser frequency noise. The intermodulation theory are further verified. Four lasers with different frequency noise are used as the laser source of RFOG system, the intermodulaion noise induced by laser frequency noise are observed, experimental results fits the theory well.(3) The resonance curve asymmetry in a RIOG(resonator integrated optic gyro) is analyzed. Four possible sources including Rayleigh backscattering polarization effect and normal mode loss difference of the coupler are compared. The normal mode loss difference of the coupler is the dominant source for the resonance curve asymmetry observed in the RIOG. When sin wave phase modulation is used to detect the resonant frequency, if the resonance curve isasymmetic, the modulation frequency difference in the modulation frequency in the two lightwaves will cause output bias in the RIOG system. Larger asymmetry and modulation frequency difference means larger output bias. Using the transmission-type resonanct cavity can eliminate the resonance asymmetry induced only by the normal mode loss difference of the coupler.In summary, the intermodulation noise induced by the laser frequency noise in a ROG system is analyzed, calculated and verified. Coupler normal mode loss difference is found to be the dominant source for the resonance curve asymmetry observed in RIOG. This will provide theoretical and experimental base for selection and optimization of the laser source and the resonant cavity.