Improved Phase Generated Carrier Demodulation for Time-Division Multiplexed FBG Accelerometers

A phase generated carrier (PGC) demodulation system for fiber Bragg grating (FBG) time-domain multiplexed accelerometers array is proposed. To eliminate environmental noise effect on the Michelson interferometer(MI), a reference FBG is used. Additionally, a PGC-improved demodulation algorithm is proposed to facilitate precise demodulation of the acceleration signal. The distortion of the demodulated signal due to modulation depth fluctuations is eliminated by constructing a quadrature signal containing only the test signal. The numerical simulation results show that the output signal of the PGC-Improved demodulation algorithm is independent of the operating point of the interferometer, the carrier delay of the modulation signal, and the modulation depth. The vibration test results of the FBG accelerometer based on the flexible hinge show that the PGC-Improved algorithm achieves a gain of 15.01 dB and 57.2 dB relative to PGC-DCM and PGC-Arctan at frequencies and accelerations of 60 Hz and 1 g. The minimum total harmonic distortion value of the PGC-Improved algorithm is 0.008 at modulation depths from 1.5 rd to 3.5 rd. The noise level of the system is approximately $4 \times 10^{-5}$ rad provided that the MI is subjected to 60 Hz perturbation.