Modulation index stabilization technique of integrated optic phase modulator used in resonant integrated optic gyro

A novel modulation index stabilization technique for tracking the phase modulation index of integrated optic phase modulator (IOPM) is proposed to improve temperature performance of the resonant integrated optic gyro (RIOG). The influence mechanism of IOPM's modulation index fluctuation on the RIOG, especially the angular velocity tracking loop of RIOG, is investigated. A Mach-Zehnder Interferometer (MZI) is ingeniously added into the conventional RIOG structure for detecting the modulation index fluctuation. For synchronously demodulating the output of RIOG and the gain of IOPM in real time, a novel six-state wave modulation scheme is also proposed. Moreover, considering the disturbance and nonlinearity, the system model of IOPM's modulation index controller is established and designed to guarantee high speed and precision tracking. The experimental results demonstrate that the proposed modulation index stabilization technique can in real time demodulate and control the modulation index of IOPM. The gyro scale factor stability of RIOG resulting from the IOPM's modulation index fluctuation is decreased to 189.26 ppm within -40°C to +60°C, which, to the best of our knowledge, is the first time stabilizing the modulation index of IOPM in RIOG at full temperature.