This invention relates to methods and apparatus for routing light beams in telecommunications devices using holographic techniques, in particular by displaying kinoforms on LCOS (Liquid Crystal on Silicon) devices. Thus we describe optical beam routing apparatus comprising: at least one optical input to receive an input beam; a plurality of optical outputs; a spatial light modulator (SLM) on an optical path between said optical input and said optical outputs; and a driver for said SLM to display a kinoform on said SLM to diffract said input beam into an output beam comprising a plurality of diffraction orders, wherein a routed one of said diffraction orders is directed to at least one selected said optical output; wherein said apparatus is configured to modify a wavefront of said output beam to reduce a coupling of said output beam into said selected optical output; and wherein said kinoform is adapted to compensate for said wavefront modification to compensate for said reduced coupling and thereby to reduce a coupling of other diffracted light from said input beam into others of said optical outputs than said at least one selected optical output.