<title>Crosstalk in packaging array-based optical interconnects and processors</title>

Abstract

Parallel optical interconnections which replace metallic transmission lines with optical fibers or free space channels provide high throughput, easy system integration, and low latency. Such interconnects are used in the design of multiprocessors and telecommunication central office switches and routers. In all parallel optical interconnects we need to couple a set of laser beams coming out of an array of sources or passing through an array of optical devices to another array of optical devices. Owing to diffraction laser beams spread spatially. So some optical d evices in the path of laser beams may receive power from adjacent channels. The power from adjacent channels gives rise to crosstalk noise. In this paper we quantify the amount of optical crosstalk that can corrupt a channel in two-dimensional rectangular arrays of parallel optical interconnects. The worst case signal to crosstalk power ratio in an array of interconnects is calculated as a function of the sizes of the array elements, inter-element spacing and distances. From the analytical results in this paper it is possible to determine guidelines on packaging optical interconnects, free -space or optical fiber-based. The effects of built-in offsets on the crosstalk power can be quantified. The results of this paper are also useful in optimizing the design of various types of e xtrinsic optical sensors in which cross-coupling or crosstalk is the basis of the sensing process.