Fully Differential Optical Interconnections for High-Speed Digital Systems

Abstract

This paper presents the design details and experimental results for a parallel optical link. The link is designed for connections within high-speed digital systems, specifically for board and backplane level interconnections. The link can contain as many fibers in parallel as technology permits. The unusual aspects of this interconnection system are that it is dc-coupled, and uses fully differential inputs, two optical channels per signal, to achieve self-thresholding and noise immunity. A chip set consisting of a 2.5-Gbps bipolar differential laser driver, a 800-Mbps GaAs MSM-preamp array, a 800-Mbps GaAs MSM-preamp-postamp array, and a GaAs MSM-preamp array with each preamp having a different bandwidth varying from 300 Mbps to 2 Gbps has been designed, fabricated, and tested to serve as a vehicle for verifying the concept. Although the experimental testing of the entire interconnect system is not yet complete, the experimental studies presented show a bandwidth in excess of 800 MHz, and excellent signal isolation between channels. © 1993 IEEE