ABSTRACT
In order to accurately locate external disturbances in a distributed fiber sensing system based on a Sagnac interferometer, a null-frequencies-seeking method of calculating autocorrelation of frequency spectrum of the interference signal is proposed and demonstrated. The average value of delay frequency intervals between the adjacent autocorrelation peaks of the interference signal spectrum is used as the null-frequency interval. The disturbance can be located by the null-frequency interval. A simulation of a Sagnac fiber-ring interferometer sensing system is built using OptiSystem software. Various disturbances acting on different positions of the sensing fiber are simulated and located. The maximum and minimum location errors within a 1 km sensing fiber are 4.5 m and 0 m, respectively. The simulation results verify that the proposed method is accurate and simple.
