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.

We report an approach to spatially map the correlation profile along the sensing fiber in Brillouin optical correlation domain analysis by pulsing the pump radiation. Simulations are carried out to demonstrate the influence of frequency modulation parameters of a narrow linewidth source on the width of the correlation profile and its peak position. The simulation results are validated through controlled experiments. The correlation profile is mapped over 1 km long fiber with spatial resolution of 1 m, limited only by the finite lifetime of acoustic phonons in the silica fiber.

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We propose a combination of frequency correlation and temporal gating techniques to map the correlation peaks, investigate their tunability through simulations and experiments. Correlation peaks in 1 km fiber are tracked with 100 ns pulses.

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