Phase Modulation Depth Evaluation and Correction Technique for the PGC Demodulation Scheme in Fiber-Optic Interferometric Sensors

Phase generated carrier (PGC) demodulation schemes are widely used in fiber-optic interferometric sensors. Basic PGC schemes required the certain value of the phase modulation depth to work properly. In this paper, a novel phase modulation depth evaluation and correction technique for PGC demodulation schemes based on the integral control feedback is presented. The proposed scheme provides the phase modulation depth stabilization to the certain predefined optimal value. Detailed theoretical analysis and mathematical modeling of the proposed scheme and the PGC-Atan demodulation scheme were performed to estimate their required parameters. The suggested technique with the PGC-Atan demodulation scheme was implemented in the field-programmable gate array-based electronic processing circuit of the single interferometric fiber Bragg grating sensor. Experimental results are consistent with theoretical analysis and the proposed scheme provides real-time stabilization of the phase modulation depth to its optimal value 2.63 rad with the standard deviation less than $5\ast 10^{-4}$ rad.