Distributed optical-fiber vibration sensing system based on differential detection of differential coherent-OTDR

A distributed optical-fiber vibration sensing system based on differential detection of differential coherent optical time-domain reflectometer (DC-OTDR) is developed in this paper. Multiple vibration sensing and positioning along the long sensing fiber are achieved using differential detection for a series of Rayleigh backscattering signals produced by single optical pulse propagating in the fiber. The experimental results show that the sensing range is more than 10 kilometers, the positioning error is less than ±3 m, and its signal to noise ratio is higher than 40.