Real-time distributed optical fiber vibration sensing based on phase-sensitive OTDR

Phase-sensitive optical time domain reflectometry (Φ-OTDR) is a promising approach for detecting and locating vibration signals along the whole fiber link. In this paper, a novel high-speed and complete signal transmission scheme based on field programmable gate array (FPGA) and universal serial bus (USB) 2.0 is proposed and applied in the Φ-OTDR system to obtain real-time vibration location. By using the novel scheme, only the effective data is selected and transmitted to the upper system for post-processing in real time. In the experiment, the vibration signals are simulated by hand-clapping, 50 Hz square waves and 400 Hz sine waves. The experimental results demonstrate that the proposed system exhibits good frequency response for vibrations below 1 kHz over 12 km fiber length. In addition, repetition vibration tests are carried out on 4.633 km and 10.022 km, and the location error is within the range of -7 m to +11 m. Therefore, the proposed system holds considerable potential for real-time vibration location and may have a wide application range in areas such as intruder detection, premier security, oil/gas pipeline leakage detection, and railway infrastructure monitoring, etc.