Harnessing path diversity for laser control in data center optical networks

Optical interconnects are already the dominant technology in large-scale datacenter networks. Unfortunately, the high optical loss of many optical components, coupled with the low efficiency of laser sources, result in high aggregate power requirements for the thousands of optical transceivers that such networks employ. As optical interconnects stay always on, even during periods of system inactivity, most of this power is wasted. Ideally we would like to turn off the transceivers when a network link is idle (i.e., 'power gate' the lasers), and turn them back on right before the next transmission. The danger with this approach is that it may expose the laser turn-on delay and lead to higher network latency. However, data center networks typically employ network topologies with path diversity and facilitate multiple paths for each source-destination pair. Based on this observation, we propose an optical network architecture where redundant paths are turned off when the extra bandwidth they provide is not needed, and they turn back on when traffic increases beyond a high watermark to decongest the network. Maintaining full connectivity removes the laser turn-on latency from the critical path and results in minimal performance degradation, while at the same time power-gating the lasers saves 60% of the laser power on average on a variety of data center traffic scenarios.