Analysis of polarization dependence of fiber optic security systems

The fiber-optic distributed disturbance sensor with dual Mach-Zehnder interferometers can be used in detecting intruder, cracks, and oil or fuel leaks. The position of the disturbance was obtained by the time delay difference between the output signals of the two Mach-Zehnder interferometers. According to the theory analysis, the records of the experiments in the major cases are compared. The polarization-induced fading phenomenon will lead to the inaccuracy of the position of the disturbance. The factors affected the system error are discussed. In order to find the relationship between the change of the environment conditions and the output states of polarization, the experiments were made. The experimental data and the simulation result on the Poincare sphere are similar.