Multi-tone approach to SBS mitigation in narrow linewidth high power fiber amplifiers

We investigate theoretically multi-tone seeding of high power ytterbium-doped amplifiers using a numerical code that solves a two-point boundary problem. A large wavelength separation among the signals is used leading to efficient transfer of power through laser gain while increasing the stimulated Brillouin scattering threshold in the channel of interest. Two-tone and three-tone seeding configurations are considered. For two-tone seeding, it is shown that a combination of narrow linewidth and broadband signals employed in a co-propagating geometry can achieve the same level of SBS suppression as counter-pumping.