Evaluation and Measurement of the Lock-in Effect in Resonant Fiber Optic Gyroscopes

This paper makes a deep investigation of the lock-in behavior in a resonant fiber-optic gyroscope (RFOG). A theoretical model is first set up to reveal the mechanism of how the backscattering creates a lock-in phenomenon at the gyro output. After phase modulation, the RFOG has more than one lock-in zone. These lock-in zones are symmetrically distributed around zero rotation rate originating from the backscattering inside the resonator, but also being affected by the modulation parameters and feedback loops. Experimentally, we tested the lock-in phenomenon in a closed-loop RFOG. The main lock-in range is measured to be 30 °/h which agrees well with the theoretical result. Finally, we successfully demonstrated the elimination of the lock-in behavior by optimizing the modulation parameters in combination with the bandwidth of the feedback loop.