Transmission-Reflection Analysis for Localization of Temporally Successive Multipoint Perturbations in a Distributed Fiber-Optic Loss Sensor Based on Rayleigh Backscattering

A novel method is presented for the localization of multipoint loss-inducing perturbations in a distributed fiber-optic sensor. The proposed simple technique is based on measurement of the transmitted and the Rayleighbackscattered powers of an unmodulated light launched into a sensing fiber. The positions of consecutive perturbations are determined by measuring the slopes of the dependence of normalized Rayleigh-backscattering power versus the square of normalized transmitted power. It is shown that these slopes uniquely depend on the positions of the disturbances along the test fiber. The method allows localization of any number of the perturbations that appear one after another at different positions along the test fiber without ambiguity. Good agreement is obtained between calculated and experimentally measured slopes for a loss that was consecutively induced near the source and remote ends of 2.844-km-long fiber.