Spatial-division multiplexed Brillouin distributed sensing based on a heterogeneous multicore fiber

Abstract

We have experimentally investigated spatial-division multiplexed (SDM) Brillouin optical time-domain analysis in a heterogeneous multicore fiber whose central core and six outer cores are made from different preforms, showing a ∼70 MHz Brillouin frequency shift (BFS) difference between them. It reveals that the heterogeneous central core and the outer cores have different temperature sensitivities, but their strain sensitivities are almost the same. By making use of the distinct temperature coefficients of these two kinds of cores, simultaneous and discriminative temperature and strain measurements are achieved. The bending-induced Brillouin gain spectrum (BGS) broadening issue in off-center cores has been clarified, and a solution has been proposed to eliminate the uncertainty caused by a bending-induced BFS shift, by averaging the BFS variations of two symmetrical outer cores. We show a new perspective for discriminative measurement in Brillouin distributed sensors based on SDM solutions.