  We report a novel technique to detect dynamic strain variations
simultaneously at multiple locations. Our technique is based on Brillouin
optical correlation domain analysis implemented through external phase
modulation to generate multiple independently-accessible correlation peaks
within the sensing fiber. Simulations are carried out to demonstrate the
precise determination of Brillouin frequency shift (BFS) from multiple
locations independently, and the corresponding results are validated through
controlled experiments. Two correlation peaks are generated within a 1 km long
fiber and their independent tunability is verified experimentally by mapping
the spatial profile of the two correlations. We demonstrate the detection of
dynamic strain variations up to 50 Hz (limited only by our test setup) at two
locations, each with a spatial resolution of 6 m over 1.1 km long fiber.
