Resonant Fiber Optic Gyroscope With HOPLL Technique Based on Acousto-Optic Modulation

Backscattering noise is a key factor to restrict the performance of resonant fiber optic gyroscopes (RFOG). In order to improve the accuracy of RFOG, this paper proposes a scheme with heterodyne optical phase-locked loop (HOPLL) technique based on acousto-optic modulation (AOM) to suppress backscattering noise. In this scheme, the main light source is divided into three output lights, two of which are frequency-shifted by the AOM, and then are phase-locked with the third light, using the HOPLL technique. The two channels of frequency-shifted light are respectively used as the clockwise (CW) and counterclockwise (CCW) light of the RFOG, and are locked on the resonance peak. The transmissive fiber resonator can be regarded as a band-pass filter. By adjusting the reference signal in the HOPLL, the carrier of the two frequency-shifted lights can be moved away from the resonance peak. The carrier light intensity of the frequency-shifted light is suppressed by the cavity itself. The suppression ratio (SPR) reaches 15.83dB. The experimental results illustrate that the bias stability of RFOG is 3.8°/h based on the Allan deviation, strongly proving the effectiveness of this scheme in suppressing backscattering noise in practical applications.