3D OPTICAL INTERCONNECTS FOR HIGH-SPEED INTERCHIP AND INTERBOARD COMMUNICATIONS

Metal connections are generally considered the most basic obstacle to continued advances in the speed of computing systems. The bottleneck of current metal-based interconnection networks is typically their very limited bandwidth. Optics, with its inherent parallelism, high bandwidth, freedom from planar constraints, and noninterfering communication, has been recognized as a possible solution to the communication problem in high-performance computing systems. This article proposes a model of 3D free-space optical interconnection network architectures for chip-to-chip and board-to-board communications. The model is intended to provide sufficiently high communication bandwidth as well as the parallelism required by massively parallel computing systems. Ln the model, interprocessor links are provided by free-space optics, eliminating all electrical links between processors. This results in a denser realization of processor arrays as well as higher interconnect densities than with electrical approaches. The authors show how to embed binary n-cube and mesh networks into the model and how to physically realize the binary n-cube network an the basis of the proposed embedding methodology using computer-generated holograms. As a relatively immature technology, optics has some disadvantages, but these are technology dependent and not fundamentally insurmountable. Ongoing research will eventually point the way to improved performance of optical switches and converting devices.