Design of erbium-doped fiber source with low relative intensity noise of FOG

Abstract

The random walk coefficient (RWC) is the index of white noise of FOG, which determines the minimum detection sensitivity of FOG. The white noise of FOG mainly focuses on optical or photoelectric detection, which can be divided into three categories: detector thermal noise, shot noise and relative intensity noise (RIN). In practice, the RWC of FOG is determined by the signal-to-noise ratio (SNR) in the phase detection process rather than the white noise. When the photocurrent is small, the SNR of FOG is determined by the shot noise. When the photocurrent is large, the signal-tonoise ratio of FOG is determined by the RIN. Therefore, the suppression of RIN is the key to improve the precision of FOG. Through the analysis of the macro input and output characteristics of semiconductor optical amplifier (SOA) and the noise spectrum analysis of saturated SOA, it is demonstrated that the gain saturation effect of SOA can effectively suppress the RIN of wide spectrum light source. Through calculation, the theoretical noise rejection ratio is more than 20dB. Therefore, an erbium-doped fiber source with low RIN is designed. The verification is carried out at the light source level and gyro level respectively. In the light source level verification, the RIN suppression effect of 10dB is achieved. In the gyro level verification, the noise suppression effect under different modulation depth is analyzed, and the random walk reduction of gyro achieves 30% - 60%.