Suppression of Phase Noise Induced by Modulation Frequency Deviation in Fiber-Optic Gyroscopes

The interferometric fiber-optic gyroscope (IFOG) is an instrument for rotational motion monitoring. In IFOGs, frequency modulation is required for noise suppression. However, when the modulation frequency is set based on a deviated eigen frequency, phase noise will increase in IFOGs. This paper proposes a novel second harmonic descent (SHD) algorithm for suppressing phase noise induced by modulation frequency deviation in IFOGs. This algorithm can obtain precise modulation frequency simply and quickly. The validity of the SHD algorithm has been verified in the static test of a IFOG. By using the SHD algorithm, the precision of measured modulation frequency can reach 0.01 Hz, and the corresponding relative error can reach 28 ppb (1 ppb = <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {1 \times 10^{-9}}$</tex-math></inline-formula>). Besides, the modulation frequency obtained by the SHD algorithm can reduce the angular random walk (ARW) by 4.5-fold, which proves the effectiveness of the suppression of phase noise.