Distributed dynamic large strain optical fiber sensor based on the detection of spontaneous Brillouin scattering

A Brillouin-based distributed optical fiber dynamic strain sensor is described which converts strain-induced Brillouin frequency shift into optical intensity variations by using an imbalanced Mach–Zhender interferometer. A 3×3 3×3 coupler is used at the output of this interferometer to permit differentiate and cross multiply demodulation. The demonstrated sensor is capable of probing dynamic strain disturbances over 2 km of sensing length every 0.5 s up to a strain of 10 mε with an accuracy of ±50 με ±50 με and spatial resolution of 1.3 m