Residual intensity modulation-induced error in resonator fiber optic gyroscopes with triangular phase modulation

The residual intensity modulation (RIM) is one of the major sources of instability in optical detection based on phase modulation. In resonator fiber optic gyroscopes (RFOGs), the RIM leads to a nonzero output signal at the resonance center frequency, which degrades the bias stability of the RFOG. While the origins of the RIM are not fully understood, we present experimental results of the RIM in the Y-branch waveguide modulator with triangular phase modulation. We establish a model to analyze the RIM-induced error in the RFOG with triangular phase modulation and pointed out that symmetrical acquisition in a triangular wave period can reduce the RIM-induced error. We experimentally study the equivalent modulation depth of the RIM with different acquisition times in a triangular wave period and symmetrical acquisition in a triangular wave period. The results show that symmetrical acquisition in a triangular wave period can eliminate the RIM-induced error.