Four-state modulation in fiber optic gyro

This paper introduces the basic signal processing principle in digital close loop fiber optic gyro, and then analyses the harmful effects of Y waveguide half-wave voltage drift on modulation gain. Based on these, the four-state bias modulation scheme is put forward and researched in detail. Compared with conventional square wave bias modulation, this method is proved to be better in controlling modulation gain drift. The signal processing circuit based on four-state modulation is designed and tested. Result shows that the four-state modulation scheme could improve the accuracy and scale factor stability of the gyro.