SLM-based optical crossbars based on the matrix-matrix principle

Describes the principles and practice of photonic switches using free space optics with channel selection by shuttering light beams using spatial light modulators. Optical fan-out is achieved using Fourier plan array generators based on binary phase only computer generated optical elements. The spatial light modulator technology considered uses arrays of ferroelectric liquid crystal pixel modulators embedded in silicon VLSI control circuitry. Under favourable circumstances, i.e. with an adequate power margin and numerical aperture margin across the switch, these appear capable of very high switch bandwidths (hundreds of Gbits/sec), and scalability to large numbers of users (hundreds). It also appears possible to make well integrated compact devices. The construction of a prototype 16×16 switch aimed at 660 Mbit/sec per channel in the LINK `Optically Connected Parallel Machines´ project is described, including its extension to a 64×64 crossbar. The practical difficulties that must be solved if the theoretical performance levels are to be approached are reviewed