Multi-point location algorithm for distributed optical fiber disturbances detection system

A novel data processing algorithm named “2-FFT” for multi-point disturbances detection and location in an in-line Sagnac sensing system is proposed and demonstrated. When multiple disturbances are applied onto the sensing fiber at the same time, the frequency response curve of the modulated phase will be superposed by each null frequency curve of the single disturbance. However, by applying a second-time FFT to the frequency spectrum, the location corresponding to each disturbance point could be simply extracted and determined. Based on the theoretical and the experimental investigation, the “2-FFT” algorithm is demonstrated to be reasonable and efficient.