A pig tracking and locating method based on distributed optical fiber vibration sensing technology

At present, the available pig tracking and locating devices can not perform online tracking continuously on the whole process but at the designated points. In order to solve this problem, it is proposed to make use of the distributed optical fiber vibration sensing technology to perform online tracking and locating of pigs. The distributed optical fiber vibration sensing system based on phase-sensitive optical time domain reflectometer (Φ-OTDR) was put up by using the one-core optical fiber of optical cable that is laid together with pipeline in the same ditch. This system was used to acquire the vibration signals which are generated during the operation of pigs, so as to analyze their time domain characteristics. It is concluded that the vibration generated during the operation of pigs is mainly caused by impacting between pigs and wall welding seams, and signal-to-noise ratio (SNR) of signals is reinforced by using the upper-lower envelope difference. Field application verifies that this technology can track and locate pigs in real time.