False Alarms Mitigation in Φ-OTDR System Using Multicore Fiber with Correlation Algorithms

Phase-sensitive optical-time domain reflectometry (Φ-OTDR) is able to detect vibrations effectively with high sensitivity. It achieves by interrogating coherent Rayleigh backscattering (RBS) light in sensing fiber. However, backscattering light in sensing fiber undergoes fading caused by phase extinction interference or polarization mismatching. Fading will result in serious false alarms when locating real vibration events, especially in weak vibration signal detection. In order to suppress interference fading and exclude false alarms to improve localization accuracy, we propose a multi-core fiber-based Φ-OTDR system. Two cores of the multicore fiber are utilized for sensing, which detect the same vibration event simultaneously. Their backscattering signals will be demodulated for locating respectively and the locating result will pass through a mutual correlation algorithm to eliminate false alarm. As a proof of the concept, experimental results confirm a very successful false alarm reduction effect. It shows great potential in smart detection of acoustic signal, such as partial discharge detection in grid.