The Gemini Project


The goal of the Gemini project is the effective exploitation of optical technology in computer interconnection networks. The focus is on tightly-coupled multicomputer systems, but the ideas are relevant to local-area network and wide-area network systems as well. To date, optics have been used almost exclusively as a link technology. Fiber links provide high-bandwidth paths from computer to switch and between switches. The switches themselves are, however, constructed using electronics, not optics. This necessitates a high-speed optical-to-electrical (o/e) signal translation at the inputs to each switch and an electrical-to-optical (e/o) translation at each swith output. It also limits the data rate to the bandwidth supported by the electronic switch.

One aspect of the Gemini project is the inclusion of optical switching in the high-bandwidth data path from computer to computer. With optical switching, we can support an all-optical end-to-end data path, eliminating the o/e and e/o signal translation and the data rate bottleneck at the switch.

Another aspect of the Gemini project is that we are not asking optical systems to perform tasks that are more well-suited to electronic systems. We are not constructing an all-optical switching system, we are constructing a dual-technology (optical and electrical) switching system that contains an optical data path and an electrical control path. In this way, optical technology is used where it provides significant advantages (e.g., high bandwidth) and electrical technology is used where it excels (e.g., logic and control).

Historical Context

Previous optical interconnect work was focused on inverted graph topologies. The following papers document this work:

Funded Activities

We are funded by NSF to build a prototype all-optical data path as a proof-of-concept for the Gemini interconnect design. We are using lithium niobate electrooptical switching elements and interconnecting them using polymer waveguides. The following publications describe various aspects of the work:

Follow-on Optical Work

After completion of the NSF grant, we continued work in the optical interconnect area for a period of time. The following publications describe this later work:


The faculty involved in the Gemini project included:

The students included:

Last modified 12 August 2006. Return to Roger's home page .

Roger Chamberlain <>