Optical free-space board-to-board interconnect: options for optical pathways

The optical free-space interconnect is becoming increasingly important because of its high intrinsic density and routing capabilities. This paper deals with a free-space board-to-board interconnect, based on light-emitting diode arrays as sources. The design of the optical pathway is discussed, and some design rules and simulation results are presented. Two basic options (a lens array and a single lens) are evaluated, and their performance, in terms of power transfer, cross talk, and uniformity, are analyzed.