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Coherent pulse compression Brillouin dynamic gratings reflectometry for slope-assisted, fast and distributed fiber strain sensing

The performance of optical time-domain sensing technique, employing the slope of Brillouin dynamic gratings in polarization-maintaining fibers, is significantly enhanced using coherent pulse compression techniques. The strain sensitivity of the reflectivity of a coded probe, orthogonally polarized to the pumps which generated the grating, depends on both pumps and probe detuning. Employing a 64 bit Golay code, the system sensitivity was enhanced eightfold, while retaining the high sampling rate of 1MHz. We report the measurement of 750Hz strain vibrations (limited by the bandwidth of the vibration source) with a spatial resolution of 20cm (limited by the bandwidth of the balanced photoreceivers).