Optical switch

An optical switch 400 comprising first and second programmable deflection planes 408, 418 to deflect beams of an optical signal to form first and second respective deflected beam arrays. A demultiplexer 405a separates light from a set of input ports 401 into component frequency channels to form incident beams on the first deflection plane. A multiplexer 405b combines the second beam array from the second deflection plane and transports the signal to a set of output ports 402. A beam steering optical element group 409 transfers the first deflected beam array from the first deflection plane to the second plane. The incidence normal of the first deflection plane is within the same angular area as the incidence normal of the second deflection plane. The dispersion direction of the second deflection beams allows the combined signals to match with the set of outputs. The optical switch may comprise mirrors, at least one lens assembly and be part of a reconfigurable optical add-drop multiplexer (ROADM). The multiplexer and demultiplexer, which may be diffraction gratings, may exhibit opposite dispersion directions. The path between the deflection planes may be of variable optical power and comprise a polarising beam splitter and a Faraday rotator.