In accordance with the invention, arrays optical sources are combined in a multilevel planar optical waveguide structure for insertion into an optical fiber laser. The basic element of the combiner is a planar array of multiple waveguides which converge and are gradually tapered to a single output waveguide. A plurality of such elements integrally formed on successive cladding layers provides a high power stack of vertically aligned outputs. An arrangement is described for using such apparatus in the amplification of optical communications signals.