Optimum modulation depth in spacecraft-borne IFOG

In order to improve the performance of spacecraft-borne interferometric fiber optic gyroscope (IFOG) in the space radiation environment by selecting a reasonable modulation depth, a model for describing the relation of the random walk coefficient (RWC) to the modulation depth is developed by analyzing the SNR of the output signal of close-loop IFOG. Simulation for the influence of radiation-induced attenuation (RIA) in the fiber, fiber length, and output power of optical source on the optimum modulation depth is performed. Results indicate that the optimum modulation depth increases with the increase of optical output power and increases with the decrease of RIA in the fiber. Moreover, the RWC corresponding to the optimum modulation depth decreases with the increase of optical output power and the decrease of RIA in the fiber. However, the optimum modulation depth decreases with the increase of fiber length of sensing coil. Furthermore, the use of overmodulation technique could deteriorate the IFOG performance when the fiber length is long and the RIA in the fiber is large. Consequently, in order to achieve the best performance, the modulation depth for IFOG must be optimized according to the actual condition during the design spacecraft-borne IFOG. Theory analysis and simulation results provide a basis for the choice of optimum modulation depth in space-borne IFOG.