Intermodal stimulated Brillouin scattering in two-mode fibers.

Characterization of stimulated Brillouin scattering (SBS) in an elliptic-core two-mode fiber is experimentally demonstrated. The LP(01) or LP(11) mode is selectively launched to a fiber under test by a mode-selective coupler as a Brillouin pump, and the Brillouin gain spectra are analyzed for different mode pairs of the pump and probe waves. Intermodal SBS between counterpropagating LP(01) and LP(11) modes is observed, and the efficiency is measured to be about 58% of that of the SBS between the LP(01) modes.