Phase Correction Based on Adaptive Fading Feedback in Distributed Fiber Acoustic Sensing Systems

Distributed optical fiber acoustic sensing is a versatile technology based on phase-sensitive optical time-domain reflectometry, capable of distributed monitoring of multipoint disturbances along a length of the optical fiber, which has been widely implemented in diverse science and engineering fields. However, for ultra-long sensing distances, the system suffers from several signal-fading mechanisms, especially those produced by interference and polarization fluctuation. As a result, the local signal intensity will be greatly attenuated, causing the phase signal to jump, making it difficult to continuously and effectively collect the disturbance signal. An adaptive phase correction method for fading suppression in distributed optical fiber acoustic sensing systems is proposed in this article. The fading-point position is obtained through differential analysis of the amplitude signal and its outlier detection. Phase correction is performed using a moving-window adjacent interpolation to achieve fading suppression. Experiments conducted in a controlled laboratory environment show that, for the piezoelectric transducer vibration signals, applying the fading suppression method results in an average increase of 12.49 dB in signal-to-noise ratio (SNR). The time required for a single moving-window processing is only 3.1 ms. During lake trials, the SNR of an underwater acoustic disturbance signal increases by 20.36 dB after applying the fading suppression method, demonstrating that the proposed method suppressed the signal distortion caused by fading effectively and could completely restore the disturbance signal.