Comparison of Optical and Electrical Links for Highly-Interconnected Systems

TL;DR

This paper compares optical and electrical links for high-speed multi-node systems, highlighting optical links' advantages for longer distances and potential to enable new HPC architectures.

Contribution

It provides experimental evaluation of optical signaling solutions, including DWDM and multimode fiber links, for multi-node compute systems, highlighting their benefits over electrical links.

Findings

Optical links support higher data rates over longer distances.

Optical solutions show advantages in power and bandwidth efficiency.

Experimental results demonstrate feasibility for HPC systems.

Abstract

As data rates for multi-gigabit serial interfaces within multi-node compute systems approach and exceed 10 Gigabits per second (Gbps), board-to-board and chip-to-chip optical signaling solutions become more attractive, particularly for longer (e.g. 50-100 cm) links. The transition to optical signaling will potentially allow new high performance compute (HPC) system architectures that benefit from characteristics unique to optical links. To examine these characteristics, we built and tested several optical demonstration vehicles; one based on dense wavelength division multiplexing (DWDM), and others based on multiple point-to-point links carried across multimode fibers. All test vehicles were constructed to evaluate applicability to a multi-node compute system. Test results, combined with data from recent research efforts are summarized and compared to equivalent electrical links and the advantages and design characteristics unique to optical signaling are identified.