Optical switch

An optical switch comprising: a first demultiplexer (diffraction grating) 405a that separates input light 401 into its component frequency channels to be incident on a first programmable deflection plane 408; beam steering optical element group 409 that deflects beams from the first programmable deflection plane to a second programmable deflection plane 414; and a first multiplexer (diffraction grating) 405b that combines the beams from the second programmable deflection plane into combined signals incident on the output ports 402. The first and second programmable deflection planes may be first and second regions on a single spatial light modulator (SLM) panel. If a non-inverted image is required on the second programable deflection plane the multiplexer and demultiplexer are made identical and the beam steering optical element group comprises four optical elements (lenses) 410, 411, 413, 415 that directs incoming beams onto a mirrored beam steering optical device 412 and out onto the second programable deflection plane. If an inverted image is required on the second programable deflection plane the multiplexer and demultiplexer are made opposite and the beam steering optical element group comprises two optical elements (lenses) (710, 715, Fig.7). The optical switch may be used in a reconfigurable optical add-drop multiplexer (ROADM) optical switch (Fig.10).