A high-stable self-referenced PGC demodulation algorithm for fiber-optic interferometric sensor

A self-referenced phase generation carrier (SR-PGC) algorithm is proposed in this paper. The influence related to modulation depth, light intensity and carrier phase delay can be theoretically eliminated. In classical PGC algorithm, the orthogonal components are obtained by mixing the detected signal with the proper multiples of carrier frequency and low-pass filtering, which are related to several parameters (modulation depth, light intensity, carrier phase delay, etc.). We notice that the differential signals of them also contain the parameters above. In the proposed SR-PGC algorithm, the orthogonal components are taken as the reference signals, and they are divided by their own differential signals, so that the parameters above can be eliminated in real-time. The algorithm was implemented in the field-programmable gate array-based electronic processing circuit, and a large dynamic range of 178.2 dB@200 Hz was achieved. Within 1 kHz bandwidth, the phase resolution reached 2 mu rad/Hz1/2. A maximum light intensity rejection ratio of 37.0 dB was obtained. While the modulation depth is between 1 rad and 3.5 rad, the signal-to-noise-and-distortion (SINAD) and the total harmonic distortion (THD) can reach as good as 74.0 dB and -76.8 dB respectively, and the fluctuation of the SINAD and THD in 4 h were both within 1.2%. These experimental results prove the high stability of SR-PGC algorithm.