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%.
The random walk coefficient of fiber optic gyroscope (FOG) is a kind of gyroscope output error accumulated over time by white noise. In order to achieve 100s bias stability of high precision FOG less than 0.0001 °/h, the random walk coefficient of FOG is less than 0.0000167 °/√ht. Based on the analysis of the factors affecting the random walk coefficient of FOG, a random walk coefficient model is established in this paper. Considering the characteristics of high precision FOG such as oversampling and low bandwidth, a method to reduce the random walk coefficient of high precision FOG is proposed. Through the theoretical analysis of the above methods, the feasibility of the method is proved theoretically. Furthermore, the comparative test of the precision of the high precision fiber optic gyroscope using the above method proves the feasibility of the above method. The random walk coefficient of the gyroscope is significantly reduced, which makes the bias stability of the high precision fiber optic gyroscope achieve the design goal.
Based on the application field of high precision Fiber optic gyroscope (FOG), high requirements are put forward for the accuracy of FOG, the stability of scale factor and the nonlinearity of scale factor. The performance of light source is closely related to the performance of these gyroscopes. Therefore, the requirements of high power, high stability, high spectral symmetry and low coherence are put forward for light source. According to the characteristics of high precision FOG, an ASE source is proposed. In the light path aspect, the physical model of ASE light source, the influence of Erbium-doped fiber length, optical path structure scheme, pump wavelength and pump power on the average wavelength of the light source are analyzed. The optical path structure and the length and pump power range of Erbium-doped fiber are determined. Through the analysis of spectral coherence, the Gauss spectrum with no sub-peak of the coherence function is selected as the filtering scheme through orthogonality. Optimize the parameters of light source by experiment and filter simulation. In the aspect of power control, improving power stability by power feedback with controlling the temperature characteristics of the feedback loop device. The ASE light source designed above can provide power output of more than 20 mW. Within operation temperature of high precision FOG, the change of wavelength stability is less than 5 ppm and the change of power output is less than 1%. It is an ideal light source for high precision FOG.