Optical switch utilising gap optics

An optical switch having a set of input ports 501 and a set of output ports 502 configured to transport an optical signal having at least one component frequency channel. A first programmable deflection plane 508 is configured to deflect beams of spatially separated frequency channels incident from the input ports to form a deflected array of beams. A second programmable deflection plane 514 receives first and second beams from the first plane which are deflected towards output ports. Between the two planes is an optical structure configured to direct the beams from the second deflection plane via a gap in projected images of an image plane of the first deflection plane. There may be a separation between the inputs of the input set. The optical structure may comprise a beam steering device 511 to create a gap between images, a mirror array (FIG. 16, 1600) having at least one mirror assembly each having two mirrors, and at least one prism 807a, 807b. A lens 506 may reside between the beam steering device and the second plane, and the inputs and the first plane. There may be a second lens between the first plane and the beam steering device.