Suppression of stimulated Brillouin scattering in optical fibers using a stepwise optical frequency pulse train

Stimulated Brillouin scattering (SBS) is a critical problem for fibers and fiber amplifiers as it severely limits single-frequency output powers; thus, we propose a seed source to mitigate it. The proposed seed source generates a high-duty-cycle N-pulse train in which the optical frequency of each subsequent pulse is shifted by a specific fixed amount with respect to the previous pulse, a stepwise optical frequency pulse train (SOFPT). In a watt-class power experiment, for a SOFPT with a 200-MHz optical frequency step, the SBS threshold for a 200-m single-mode fiber was enhanced by a factor of N compared with that for the CW seed source.