Combined frequency-locking technology of a digital integrated resonator optic gyroscope with a phase-modulated feedback loop.

In the resonator fiber optic gyroscope (RFOG), the conventional laser feedback loop is realized by adjusting the laser central frequency to tracking the resonance point of the resonator. This method generally relies on the laser tuning coefficient and digital-to-analog converter, which inevitably produces quantization error and limits frequency-locking accuracy and gyro resolution. In addition, the output drift caused by low-frequency noise also is a problem with long-term lock-in tests. In this paper, a novel and simple combined frequency-locking technology based on a phase-modulated feedback loop and a laser feedback loop is proposed by using the high-precision tuning of a phase modulator to improve the resolution and suppress the low-frequency drift. Furthermore, it has been proved by experiments that the resolution is increased by 10 times, while the frequency-locking accuracy is improved from 10°/s to 0.5°/s by using the combined frequency-locking mode. In addition, the low-frequency drift is eliminated with the long-term lock-in of RFOG, and the system resolution from 1°/s to 0.1°/s is accurately displayed.