Brillouin standing wave reflectometry (BSWR): A novel approach for high sensitivity, fast and distributed strain sensing in optical fibers

We demonstrate a novel distributed fiber sensing technique with a record broadband sensitivity of 10nİ/√Hz at a sampling rate of 1MHz. A standing acoustic wave is generated by all-optical excitation of two simultaneously counterpropagating Brillouin dynamic gratings. A dual-tone readout probe pulse is used for the distributed measurement of strain-induced nonlinear phase-shifts of the acoustic wave. The phase is demodulated in electrical domain from the beat note of the reflected probe following the hardware-simpler direct detection. The measurement of 5kHz strain vibrations with a spatial resolution of 20cm (limited only by the 0.5ns switching time of our SOA) is reported.