Research on the Modulation Phase Distortion Error Character of Y Wave-Guide in Fiber Optic Gyroscope

Y wave-guide is an essential component in the close-loop interference fiber optic gyroscope (IFOG) system. The application of Y wave-guide in IFOG enables FOG to have high scale factor linearity and has significantly improved scale factor stability and repeatability. The main function of Y wave-guide is polarizing, coupling and modulating the phase. Phase modulated includes double hands in IFOG. On one hand, the pi/2 phase is biased by square waves, and on the other hand, ladder waves is used to compensate Sagnac phase. In fact, both square waves and ladder waves have very high frequency, including multiple harmonic waves and easily being disturbed. The signal quality of square waves and ladder waves have great effect on drift and zero-bias of the IFOG. Focusing on different phase error factors in Y wave-guide, it makes modulation signals to be best state by adopting corresponding means to restrain and insulate error sources based on theoretical analysis of modulation phase distortion error character in IFOG. The result of measurement shows that modulation phase distortion error is degreased distinctly after improving the signal quality of square waves and ladder waves, and meets the demand of high precision of IFOG.