Optical Bus Extenders for High Speed Computers,

A bus extender is a means for high-speed interconnection of a multitude of individual computing modules comprising a distributed computing system. When the elements to be interconnected are spaced by distances of more than a very few meters, there are significant advantages to the use of optics for providing the interconnects. The feasibility is being examined of using optical bus extenders in a strategic defense system. The advantages and limitations of both free-space communication and fiber communication over short distances are being determined. Critical issues are the bulk and cost of components, and the efficiency with which light can be detected at the end of the various links. Optimization of certain parameters of the extender are being explored with respect to both cost and performance. The general results obtained are being applied to the special case of the VME bus. Protocols to control activity on the extender are being considered and a preferred solution is being proposed. As issues arise that can be resolved only by breadboarding a collection of components or a small subsystem, then such breadboarding is being undertaken. The problem of simultaneously mapping the state of the bus to several remote locations is being examined. Various methods for tapping the optical energy for multiple destinations are being considered and the optical efficiency and cost of these solutions are being determined.