A low cost all-digital demodulation method for fiber-optic interferometric sensors

Presented in this paper is a novel digital demodulation method for fiber-optic interferometric sensors. The method controls the modulation depth at pi/2 radians and uses only five key points sampling values every modulation period. Both an automatic accurate sampling method and a modulation depth control method are introduced. Fewer resources are needed for the calculation processes to obtain the phase shift. High speed A/D convener is not necessary, which results in significant reduction of the manufacturing cost of fiber-optic interferometric sensors. A bias stability of 0.64 deg h(-1) (i.e. 2.23 mu rad) is demonstrated after using this method on an interferometric fiber-optic gyroscope (IFOG) based on the Sagnac effect.