Research and application of a perimeter security system based on distributed optical fiber acoustic sensing using UWFBG

This paper addresses the significant challenges of low signal-to-noise ratio (SNR) and difficulties in event reconstruction and identification faced by conventional distributed acoustic sensing (DAS) technology in perimeter security applications for coastal defense environments. We developed a novel perimeter security system based on an Ultra-Weak Fiber Bragg Grating (UWFBG) array integrated with a self-heterodyne detection structure. The system was deployed and comprehensively validated on an island reef outpost under real-world operational conditions. Compared to traditional systems utilizing standard single-mode fiber (SMF), the background noise of signals collected by the new system under natural, non-intrusion conditions was significantly reduced. For two typical intrusion events—human knocking and assault boat landing—the average SNR was improved by 8.02dB and 9.95dB, respectively. Experimental results demonstrate that the proposed system maintains high sensitivity and strong anti-interference capability in complex coastal environments, providing crucial technical support for the engineering implementation of perimeter security in key coastal defense areas such as islands, reefs, and ports.