Distributed Acoustic Sensing System Utilizing Phase-OTDR Integrated With One-Way Ring SI via Undersampling Recovery Algorithm

In this article, a novel integrated vibration sensing system based on phase sensitive optical time-domain reflectometer (phase-OTDR) and one-way ring Sagnac interferometer (RSI) is proposed and demonstrated. Based on the relationship between the reflectometer and interferometer phase signal spectra, a cross-correlation algorithm is introduced for undersampling judgment. By mapping the undersampled frequency to the real frequency, the vibration signal is correctly recovered to improve the system frequency response range. The proposed signal recovery algorithm can accurately reconstruct individual signals when multiple vibration spectra do not overlap. In addition, the demodulation result of the interferometer is used as the output signal when the vibration signal amplitude exceeds the detection range of the reflectometer to improve the dynamic range of the system. Experimental results show that the system achieves correct demodulation of low-frequency, high-frequency, wide-frequency, and multipoint vibration. Thus, the proposed system is crucial for advancing distributed fiber optic sensing applications.