Optics in data center: Improving scalability and energy efficiency

Interconnection networks within modern data centers suffer from bandwidth and scalability limitations, and important power consumption. Optical switching solutions can help to overcome such issues when properly designed and optimized. This paper discusses three areas of improvement beyond state of the art: i) the use of more energy-efficient optical devices to realize high-capacity and energy-efficient optical space switches; ii) the enhancement of their scalability by combining space switching with time switching into a space-time interconnection network architecture (STIA); iii) the planning of an energy-efficient STIA-based network meeting data center bisection bandwidth requirements. Performance assessment shows that i) by combining different switching devices in the same space switch, up to 90% of the power can be saved with respect to conventional SOA-based space switches; ii) STIA allows scalability to increase by a factor of 8, thanks to the combined use of space and time switching domains, while limiting the energy per bit; iii) STIA allows the realization of data center topologies, such as folded Clos and flattened butterfly, whose optimized design can lead to power saving up to 50% with respect to an energy unaware design.