A wavelength division multiplexer utilizes an optical source in the form of at least two separate laser array components, each laser array component including a group of laser diodes operating at wavelengths that are spaced by a multiple of the pre-defined channel spacing of the multiplexer. This optical source thus generates a plurality of non-sequential optical signals that need to be re-ordered at some point along the signal path so that all of the signals are multiplexed onto a single output signal path. The multiplexer utilizes an arrayed waveguide grating (AWG) to combine the various optical signals, with a specialized apparatus for re-ordering the non-sequential wavelengths of the propagating plurality of N optical signals disposed either at the input or output of the AWG.