Layout model for optical interconnects based on λ-routing grids and topology embeddings

Optical technology is being promoted as a highly promising, energy-efficient interconnect solution for next generation data centers and high performance computing systems. To overcome the energy and bandwidth limitations of electrical interconnects, all-optical technologies will be deployed at even shorter distances in the near future (board-to-board, on-board, and on-chip). On-board layout models for electronic interconnects, including the Thompson model [J. Comput. System Sci., vol. 28, no. 2, pp. 300, 1984], have long been proposed in the literature and corresponding area-efficient layouts have been found [Int. Conf. Parallel Processing, 2000] for a number of popular topologies. However, optical on-board interconnects have important differences from electrical ones, requiring the introduction of appropriate layout models for them. In this work, we look into the differences between electronic and optical on-board layouts, and propose optical interconnection layout models. In particular, we examine λ-routing grids for on-board optical interconnects in which routing options other than the traditional vertical-horizontal one are used (λ is the number of permitted routing options). We define 2D mesh topologies, based on the proposed λ-routing grids, achieving better bisection width and bisection width over area ratios than with rectangular (λ = 2) grids. We also propose topologies with high connectivity degrees that fit the examined λ-routing grids and present their on-board layouts.