Multi-point Dynamic Strain Sensing using External Phase Modulation-based Brillouin Optical Correlation Domain Analysis

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.