Discriminative Temperature and Strain Sensing in a Few-Mode Optical Fiber by Stimulated Brillouin Scattering

In this work, we demonstrate the use of Brillouin scattering in few-mode optical fibers for discriminative strain and temperature sensing. It is shown that the modal birefringence of the vector modes composing the LP11 mode group, which can be measured by any high-resolution Brillouin sensor scheme, varies with temperature and strain with opposite sign. Combining modal birefringence and Brillouin frequency shift (BFS) measurements along the same fiber, temperature and strain can be discriminated. Proof-of-concept experiments were carried our utilizing a 180-m long, graded-index few-mode-fiber (FMF) and a Brillouin optical frequency-domain analysis (BOFDA) configuration, demonstrating the feasibility of the proposed approach.