Abstract: A semiconductor pump laser uses a depolarzer to depolarize the pump light entering the fiber amplifier. The depolarized light source is useful for reducing polarization dependent gain of fiber amplifiers. The pump laser includes one or more semiconductor, coherence-collapsed laser sources emitting polarized pump outputs, and one or more depolarizers disposed to depolarize the polarized pump output from the lasers. One or more fiber outputs are coupled to the one or more depolarizers to receive depolarized pump light. The depolarizer may include an N×M polarization preserving coupler having N inputs and M outputs, N and M being at least 2, an input to the depolarizer at a first coupler input, an output port from the depolarizer at a first coupler output. A polarization-controlling optical path is coupled between a second coupler output and a second coupler input.