Analyses and experiments of effects of square wave modulation errors on fiber optic gyroscope

It is isindicated that square wave modulation errors are caused by non-ideal frequency, phase and duty cycle of the square wave based on the principle of square wave modulation and demodulation in digital closed-loop Fiber Optic Gyroscope (FOG). The frequency and phase characters of the periodic pulse interference were discussed. Meanwhile, the mathematical model of square wave modulation errors were formulated by applying Fourier series of the periodic pulse interference. A simplified model of closed-loop FOG with the square wave modulation errors was developed, and a relational expression between the square wave modulation errors and the bias error of closed-loop FOG was obtained. The effects of the square wave cycle, phase, duty cycle and the fiber coil group delay and amplifier gain bandwidth on the bias error of closed-loop FOG were analyzed by simulating and testing. A simple method was presented to detect the square wave modulation errors via the waveform of the periodic pulse interference.