A Novel Phase Demodulation Method and Simulation for Fiber-Optic Distributed Acoustic Sensor

Fiber-optic distributed acoustic sensors (DASs) can be used for various applications, such as seismic wave detection, geological exploration, and large-scale structural health monitoring. Phase-sensitive optical time-domain reflectometer (Φ-OTDR) is one of DAS’s most common technical schemes. In this paper, a novel phase demodulation method for DAS is proposed. In this proposed method, four pairs of probing pulses are used to construct in-phase and quadrature (IQ) components for phase demodulation. Compared to the conventional quadrature demodulation method, this method simplifies the system. The scaler model of Φ-OTDR and phase demodulation algorithm are revealed in theory and simulation. Simulations confirm the validity of the proposed method. The demonstrated phase demodulation method achieves ~ 80 dB of SNR, capable of vibroacoustic perturbations along the same line. It has good potential in low-cost and long-distance health structural health monitoring.