  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.
