High-Spatial- and Spectral-Resolution Time-Domain Brillouin Distributed Sensing by Use of Two Frequency-Shifted Optical Beam Pairs

We present a novel scheme aimed to improve spectral resolution in Brillouin distributed sensors based on single-mode standard fibers. The method makes use of two frequency-shifted optical pairs, the first one (the "writing" pair) devoted to excite the acoustic wave and the second one (the "reading" pair) employed to perform Brillouin gain interrogation. A numerical analysis demonstrates the capability of the method to ensure high spectral resolution even when operating in the high-spatial-resolution (~1 m or less) regime. Preliminary experimental results carried out at 1-m spatial resolution are also reported.