Abstract

The recent development of large two-dimensional arrays of digital, optically bistable devices has facilitated the construction of test-bed, free-space switching systems^1,2. This paper discusses aspects of the design and operation of these systems. Free-space switching systems may ultimately provide larger interconnection density than conventional electronic techniques. It is proposed that they therefore provide the switching fabric. The fabric is the part of the switch which routes data from the input to the required output. The input to the switch is not in a format suitable to send directly to the fabric. It includes the routing information required by the computer controlling the switch, the path hunt processor, and signalling protocol information that must be extracted and processed. The input data must also be re-synchronized and bit-aligned. Therefore, the operating wavelength of the fabric is unconstrained. It does not need to match the transmission wavelength. Similarly, with demultiplexing, the fabric data rate does not need to match the transmission data rate. Each array of logic gates provides data regeneration in a manner similar to electronic gates. Thus, although the devices must switch states at the fabric data rate, high output contrast is not required. Any comparison with systems using data ‘transparent’ devices, such as lithium niobate waveguides, is complicated since they operate as relational rather than logical devices.

© 1991 Optical Society of America