A system and method for efficiently combining multiple laser beams into a single frequency by invoking stimulated Brillouin scattering (SBS) in a dual core optical fiber is disclosed. The method and apparatus essentially becomes a brightness converter for the input laser beams. An SRS seed is generated in a long length of fiber or by a diode and is launched into the back-end of the SBS combining optical fiber. Various single-frequency pump beams are launched into the front-end of the same fiber. The seed acts to lower a threshold for SBS in the fiber, thus invoking the nonlinearity. Provided the various pump beams are close in frequency and seed/pump modes overlap, each acts to amplify the seed through the nonlinear SBS process, providing an output signal which is brighter than the combined pump beams.