Distributed Vibroacoustic(Acoustic) Systems (DVS/DAS) is a set of long-distance, distributed, accurately located vibration monitoring system, the system is based on the principle of φ-OTDR, the use of high-coherence backward Rayleigh scattering of light interference phenomenon, with the ordinary communication cable itself as a sensing device, can detect a few kilometers to tens of kilometers of optical fiber vibration, the spatial sampling interval of only 1m, the detection cycle can be up to milliseconds. The detection period can be up to milliseconds.

When the light pulse propagates to the fiber optic section which is subjected to external vibration signal, its Rayleigh scattering back to the detector will also produce changes in the optical signal, through the detection of changes in the scattered light signal can be detected by the vibration of the measurement area, at the same time, through the pattern recognition algorithm can be accurately judged a variety of different invasion and destruction methods, and can simultaneously achieve multi-point invasion of the same time to monitor and accurately locate. The system can be applied to the safety monitoring and positioning of oil and gas pipelines, communication lines, power transmission cables, etc.; it can be used for the invasion safety protection in important areas, such as the invasion monitoring of pipe corridors, the positioning of people in pipe corridors, and the monitoring of pipe corridors collapsing. The characteristics of this technology are: long measuring distance, real-time, distributed measurement, high accuracy, high sensitivity, good electromagnetic insulation, free from electromagnetic interference, intrinsic lightning protection, intrinsic safety, simple construction and easy maintenance.

DVS system includes light source, AOM, EDFA, WDM, balance detector, acquisition card, computer analysis software, etc. DAS system compared to the DVS system is more sensitive, able to phase demodulation, linear restoration of the sound, DAS data acquisition needs to be demodulated IQ signal, so the acquisition card needs to be higher compared to the acquisition card bandwidth of the DVS card. The software layer is more complex than DVS.