Brillouin scattering in multi-core optical fibers

We measure the Brillouin gain spectra in two cores (the central core and one of the outer cores) of a ~3-m-long, silica-based, 7-core multi-core fiber (MCF) with incident light of 1550 nm wavelength, and investigate the Brillouin frequency shift (BFS) and its dependence on strain and temperature. The BFSs of both the cores are ~10.92 GHz, and the strain- and temperature-dependence coefficients of the BFS in the central core are 484.8 MHz/% and 1.08 MHz/K, respectively, whereas those in the outer core are 516.9 MHz/% and 1.03 MHz/K. All of these values are not largely different from those in a silica single-mode fiber, which is expected because the cores are composed of the same material (silica). The difference in the BFS dependence of strain between the two cores may originate from the difference in structural deformation when strain is applied to the fiber, which is a unique characteristic to MCFs. The future prospect on distributed strain and temperature sensing based on Brillouin scattering in MCFs is finally presented.