Abstract

A free-space optical interconnection has zero insertion force and no ground planes. Low propagation delays are possible in board-to-board applications because of the direct path between interconnected points compared to the circuitous path often required by electrical interconnections. The optical channel has very high bandwidth and low dispersion. Furthermore, very high interconnection densities are possible because light beams can cross in free space. However, high­speed optoelectronic components are typically small and difficult to align in a computer environment. Experimental free-space optical interconnections have required the use of micropositioners for alignment and are not readily adapted for conventional computers.¹ In this work, techniques for the practical implementation of high-speed board-to-board free-space optical interconnections without micropositioners have been developed. A free-space transmitter and receiver module combined with a card cage board enclosure designed for the application have made possible a differential electrical current efficiency (detector photocurrent divided by laser drive current) as high as 8%.

© 1991 Optical Society of America