Distributed and dynamic monitoring of 4km/sec waves using a Brillouin fiber optic strain sensor

Abstract

We report a Brillouin-based fully distributed and dynamic monitoring of a strain wave, propagating at a speed of ~4km/sec in a 6m long fiber. Using an audio speaker, a mechanical impulse was introduced to one end of a 6m long optical fiber, initiating a strain wave propagating towards the other fixed end of the fiber. Employing a simplified version of the Slope-Assisted Brillouin Optical Time Domain Analysis (SA-BOTDA) technique, the whole length of the fiber was interrogated every 1μs (before averaging). A dynamic spatially and temporally continuous map of the strain was obtained, from which the wave velocity could be deduced. With a trade-off among sampling rate, range and signal to noise ratio, kHz sampling rates and hundreds of meters of range can be covered with spatial resolutions down to a few centimeters.