Online RWE monitoring based on cross-correlation method for IFOGs in space applications

Random Walk Error (RWE) is one of the most sensitive errors in interference fiber optic gyroscopes (IFOGs) for space applications. Based on the optical component parameters that degrade in space irradiation environment and the IFOG physical model, forward path gain (FPG) is confirmed as the feature characterizing deterioration of RWE. According to the cross-correlation identification theory, an online FPG extraction method with pseudo random binary signals(PRBS) injection is proposed. The correlativity between the forward path output, square-wave reference signal and square-wave modulated PRBS are analyzed, and the results show that the extraction process can identify the FPG effectively without disturbing IFOGs' normal working cycles. The prerequisite of the method is discussed and the hardware realization in IFOG is introduced. An IFOG gamma ray radiation experiment was carried out to verify the method and the results shows that the FPG identification process can reveal 75% deterioration of RWE.