Accurate Brillouin frequency shift measurements using a hybrid Brillouin optical frequency/correlation domain analysis.

We report a hybrid Brillouin optical frequency/correlation-domain analysis technique, capable of accurate and high spatial resolution Brillouin frequency shift (BFS) profile measurements in optical fibers. The method relies on a conventional Brillouin optical frequency domain analysis (BOFDA) configuration, with an additional sinusoidal frequency modulation (FM) applied to the pump and probe beams. Such frequency modulation synthetizes a sequence of narrow correlation peaks along the fiber, which are simultaneously interrogated through BOFDA. Localizing the acoustic wave at the correlation peak positions, the artifacts that usually affect BOFDA measurements are efficiently removed, improving the measurement accuracy. Experiments demonstrate the technique in a 1.35-km sensing fiber at a spatial resolution of 6 cm.