Optical interconnections and their impact on computing

Summary form only given, as follows. A computing system can be regarded as a collection on nonlinear gates, within which signals must interact, and interconnections between those gates and between groups of gates for communications. The use of optics at an interconnect technology is addressed. The appropriateness of optics as an interconnect solution varies through the hierarchy of levels of interconnect present in computing. At the machine-to-machine level there is no argument about the success of optics as an interconnect medium. At the lowest level, gate-to-gate, it can be shown that optics will probably not be competitive with electronic solutions. Somewhere between the highest level and the lowest level there is a level where optics becomes noncompetitive. Just where this level may be is a subject of much interest and research. From the knowledge now in hand, it appears likely that optics will provide a competitive advantage at those levels where terminated transmission lines would otherwise be required. However, the relatively short lifetimes (less than 100 h) of laser diodes will limit the number of such devices that can be used within a single machine and therefore will influence how low in the interconnect hierarchy optics can penetrate.<>