Transmission/reflection analysis for localization of loss-inducing perturbations in distributed fiber-optic sensor based on Rayleigh backscattering

We present a simple method for the localization of a loss region for a fiber-optic alarm-condition sensor based on the measurement of transmitted and Rayleigh backscattered power. Bending the sensing fiber affects both the transmitted and backscattered power of unmodulated continuous-wave light that is launched into the fiber. The position of the loss region is determined from unique relationships between normalized transmitted and backscattered powers for different locations of the disturbance along the test fiber. The localization of a strong disturbance with an estimated accuracy of few meters along a few km-length single-mode test fiber was demonstrated.