Signal processing improvement of passive resonant fiber optic gyroscope using a reciprocal modulation-demodulation technique

Abstract

A resonant fiber optic gyroscope (RFOG) based on the reciprocal phase modulation-demodulation technique is proposed and demonstrated. The residual amplitude modulation induced error of the phase modulator, and the effect of laser frequency noise are all suppressed thanks to the reciprocity of the proposed signal processing scheme. Compared with the past separate modulation-demodulation RFOG, the angular random walk is improved by a factor of 15 times from 0.08°/√h to 0.0052°/√h, and the bias stability is improved from 0.3°/h to 0.06°/h.

Residual Intensity Modulation Induced Error in Resonator Fiber Optic Gyroscopes With Reciprocal Detection

“…The error mechanisms drive the design improvement of the RFOG [4][5][6][7]. However, the error induced by the residual intensity modulation (RIM) of the electro-optical phase modulator (EOPM) and the backscattering-induced noise have typically driven designs in different directions [3].…”

“…The suppression of the backscattering-induced noise requires that the frequencies of CW and CCW phase modulation are different to reduce the same frequency components of the CW and CCW light waves [8,9,10]. However, the suppression of the RIM-induced error expects that the phase modulation-demodulation scheme is the same for the CW and CCW resonance detection [4,11]. One requires different phase modulations in the CW and CCW directions, and the other requires the same phase modulation in the CW and CCW directions.…”

“…Therefore, the backscattering-induced noise is the main concern [12,13]. However, as the precision of the RFOG continues to improve, approaching the inertial navigation grade, the RIM-induced error has gradually attracted attention [3,4,14]. Both the RIM-induced error and the backscattering-induced noise need to be effectively suppressed.…”

“…Sanders et al proposed an improved modulation technique in a three-laser RFOG configuration to reduce the drift due to optical backscatter while retaining a common modulation for CW and CCW resonance detection to eliminate the RIM-induced error [3]. Jiang et al established the model of the RIM-induced error in the RFOG with triangular phase modulation [14], and demonstrated an improved modulation scheme to suppress the backscattering-induced noise while reducing the RIM-induced error [11].Ma et al theoretically analyzed the RIM-induced error in the RFOG with sinusoidal wave phase modulation [15], and proposed the RFOG using reciprocal detection [4], where the CW and CCW resonance detection are realized by the same phase modulation and demodulation, and the backscattering induced noise is suppressed by adding other phase modulators for frequency shift (PMFS). In Ref.…”

“…In Ref. 4, the analysis shows that the error induced by the RIM of the phase modulator used for resonance detection (PMD) can be effectively suppressed in the RFOG with reciprocal detection. However, the influence of the RIM of the PMFS on the performance of the RFOG with reciprocal detection has not been analyzed.…”