Brillouin gain analysis for fibers with different refractive indices.

We studied an anomalous result in the measured stimulated Brillouin scattering threshold for single-mode optical fibers with different refractive index profiles and effective areas. It was found that, in addition to the optical effective area, the refractive-index-dependent interaction between the optical and the acoustic fields must be considered in order to account for the differences in the stimulated Brillouin scattering threshold between fiber types. A detailed analytical formalism describing the acousto-optic interaction was derived to accommodate the influence of the index profile design on Brillouin scattering.