Speed and energy comparison between electrical and electro-optical interconnects and application to optoelectronic computing

The performance of VLSI systems become increasingly more dominated by the performance of long interconnects. To overcome this limitation, free-space electro-optical interconnects have been suggested, where long electrical interconnects are replaced by an electrically-driven optical transmitter, a photodetector, and interconnection optics between them. Such electro-optical connections, although devoid of electrical interconnection parasitics, have their own difficulties. Unavailability of monolithically integrated optical transmitters on silicon imposes hybrid integration schemes with larger parasitic capacitance and increased cost. Transformation of information from electrical to optical domain and vice versa introduces severe inefficiencies into the energy budget. There are voltage incompatibility issues between some optical transmitter technologies and VLSI technology as well.;It is therefore essential to clarify the regions of superiority between electrical and electro-optical interconnects, and identify some of the important trade-offs. This thesis covers the study of electrical and electro-optical interconnections within a globally connected computing machine, presents the comparison of intrachip, inter-chip, wafer-scale and module-level electrical and electro-optical interconnections, demonstrates a region of superiority of electro-optical connections, and illustrates the application of such electro-optical interconnects to parallel optoelectronic computing machines.;Chapter I presents a study of electrical versus electro-optical interconnections in terms of data transmission speed and energy per bit transmitted. Chapter II presents the implementation of a 3-dimensional neural network prototype system where inter-neuron communications are electro-optical. Large-scale neural network implementations require long fan-out and fan-in connections which highly benefit from electro-optical implementations. Chapter III presents the application of electro-optical interconnects to processor-to-massive storage connections in optoelectronic database machines. Parallel direct optical access to mass memory enables high data throughput, larger than possible using serial electrical access techniques. Optoelectronic associative memory and correlator systems have been investigated. In Chapter IV, the application of electro-optical connections to a general purpose, 3-D computer architecture is presented and advantages are illustrated.