A wavelength division multiplexed, WDM, reconfigurable optical switch, the switch comprising: at least one optical input port to receive a WDM input optical signal comprising a plurality of wavelength channels; a plurality of optical output ports; a reconfigurable holographic array on an optical path between said at least one optical input port and said plurality of optical output ports; and at least one diffractive element on an optical path between said at least one optical input port and said reconfigurable holographic array, to demultiplex said WDM input optical signal into a plurality of demultiplexed optical input beam channels, and to disperse said demultiplexed optical input beam channels spatially along a first axis (N x) on said reconfigurable holographic array; wherein said reconfigurable holographic array comprises an array of configurable sub-holograms (112, 112'), said array extending along said first axis, wherein a sub-hologram is configured to direct a demultiplexed optical input beam channel to a respective selected one of said optical output ports; and wherein the switch further comprises one or more beam profiling optical elements to modify transverse beam profiles of said demultiplexed optical input beam channels to modified beam profiles, wherein a said modified beam profile comprises a beam profile having one or more characteristics selected from a group consisting of: a flattened beam profile, a steeper-sided beam profile, and a beam profile which substantially fits a rectangular envelope, and wherein said one or more beam profiling optical elements are configured to modify said transverse beam profiles of said demultiplexed optical input beam channels such that a transverse spatial dimension of a demultiplexed optical input beam channel substantially matches a corresponding transverse spatial dimension of a said sub-hologram on said reconfigurable holographic array. at least one optical input port to receive a WDM input optical signal comprising a plurality of wavelength channels; a plurality of optical output ports; a reconfigurable holographic array on an optical path between said at least one optical input port and said plurality of optical output ports; and at least one diffractive element on an optical path between said at least one optical input port and said reconfigurable holographic array, to demultiplex said WDM input optical signal into a plurality of demultiplexed optical input beam channels, and to disperse said demultiplexed optical input beam channels spatially along a first axis (N x) on said reconfigurable holographic array; wherein said reconfigurable holographic array comprises an array of configurable sub-holograms (112, 112'), said array extending along said first axis, wherein a sub-hologram is configured to direct a demultiplexed optical input beam channel to a respective selected one of said optical output ports; and wherein the switch further comprises one or more beam profiling optical elements to modify transverse beam profiles of said demultiplexed optical input beam channels to modified beam profiles, wherein a said modified beam profile comprises a beam profile having one or more characteristics selected from a group consisting of: a flattened beam profile, a steeper-sided beam profile, and a beam profile which substantially fits a rectangular envelope, and wherein said one or more beam profiling optical elements are configured to modify said transverse beam profiles of said demultiplexed optical input beam channels such that a transverse spatial dimension of a demultiplexed optical input beam channel substantially matches a corresponding transverse spatial dimension of a said sub-hologram on said reconfigurable holographic array.