Suppression of the interference fading in heterodyne Φ-OTDR with fast signal synthesis algorithm

Abstract With the increasing diversity of application scenarios, there is a growing demand for distributed acoustic sensing (DAS) systems to monitor the environment without false alarms. In DAS system based on phase-sensitive optical time-domain reflectometry (Φ-OTDR), interference fading significantly lead to a large number of false alarms in the system, which affecting the system’s monitoring capability. Before the phase demodulation process, Φ-OTDR system generally requires additional time for interference fading suppression. Therefore, the rapid acquisition of a fading-free signal before phase demodulation benefits the use of Φ-OTDR in real-time demanding scenarios. In this paper, based on the time-domain stitching and complex-field moving average, a fast signal synthesis (FSS) algorithm is proposed, enabling the quick synthesis of signals while maintaining fading suppression performance. Experimental results show that the signal intensity obtained by FSS algorithm fluctuates within 27 dB, while the intensity of the conventional denoising algorithm fluctuates more than 50 dB. Meanwhile, this method is more rapid than the rotated-vector-sum (RVS) algorithm, and the time consumption of signal synthesis is only 26.58% of that of the RVS algorithm. FSS algorithm provides a new and faster way to synthesize signals for interference fading suppression. Benefiting from this, FSS algorithm further improves the real-time performance of the Φ-OTDR system.