Abstract: A wavelength division multiplexed (WDM) reconfigurable optical switch. The switch has a set of arrays of optical beam connections, each comprising an array of optical outputs and having an optical input to receive a WDM input optical signal; a first diffractive element to demultiplexed the WDM input optical signal into a plurality of demultiplexed optical input beams, and to disperse said demultiplexed optical input beams spatially along a first axis; first relay optics between the set of arrays of optical beam connections and the first diffractive element; and a reconfigurable holographic array comprising a 2D array of reconfigurable sub-holograms defining sub-hologram rows and columns.