Impact of Technological Advances and Architectural Insights on the Design of Optical Computers

Communication problems such as interconnection bandwidth, clock skew, and connectivity are restricting computational throughput. Bandwidth and clock skew problems limit the speed and add to the design complexity of a processor. Constrained connectivity forces much of the speed of a processor to be used to compensate for the limited number of interconnections. Philosophically, the large bandwidth, innate parallelism and non-interfering propagation of optics offer mechanisms for overcoming these communication problems. The difficulty in exploiting these capabilities has been the absence of suitable optical logic and memory devices. Advances in optical nonlinearities offer the possibility of cascadable optical logic gates that are competitive with electronics. Advances in computer architecture can be used to simplify the optical memory requirements and utilize the large bandwidth, parallel, non-interfering communications of optics. Current computers suffer from several communication problems that limit their computational throughput, such as bandwidth, clock skew and the Von Neuman bottleneck. The bandwidth and clock skew problems limit the speed and add to the design complexity of a processor. The Von Neumann bottleneck forces much of the speed of a processor to be used to compensate for the limited number of interconnections. Philosophically, the large bandwidth, innate parallelism and non-interfering propagation of optics offer mechanisms for overcoming these communication problems. Historically, the development of optical processors has suffered from the lack of suitable logical and memory devices. Recent advances in optical bistability offer the possibility of cascadable optical logic gates with speeds and power consumption competitive with electronic gates. A parallel pipelined architecture can be shown to simplify the optical memory requirements; utilize the large bandwidth, parallel, non-interfering communications of optics; and solve some of the expected problems assiciated with using optical technology that operates on a femtosecond timescale.