Characterization of stimulated Brillouin scattering in a few-mode fiber.

Characterization of stimulated Brillouin scattering (SBS) in a few-mode fiber (FMF) is experimentally demonstrated, where the Brillouin gain spectrum (BGS) of intramodal or intermodal SBS is analyzed for different pump-probe pairs of four LP modes--LP(01), LP(11), LP(21), and LP(02) modes--guided in the fiber. A mode-division multiplexer composed of concatenated mode-selective couplers is applied for selective launching of each LP mode, and a differential measurement scheme is adopted for the analysis of the BGS. The intermodal SBS is observed in each pump-probe pair of different modes, and the Brillouin gain is measured to be within 14%-45% of that of the SBS between the LP(01) modes. The SBS threshold of each LP mode in the FMF is also evaluated.