An Energy-Efficient Optically Connected Memory Module for Hybrid Packet- and Circuit-Switched Optical Networks

Demands on future data centers and high-performance computing systems will require processor-memory interconnects with greater performance and flexibility than can be provided by existing electronic interconnects. The bandwidth density and bit-rate transparency offered by optical systems are uniquely suited to address these challenges facing memory interconnects. We, thus, investigate a hybrid packet- and circuit-switched optical interconnection network linking microprocessors with their associated main memory, which can simultaneously reduce memory access latency and improve energy efficiency performance. This novel hybrid approach allows low-bandwidth memory control data and small memory transactions to be efficiently transmitted as wavelength-striped optical packets, while long bursts of memory accesses are optically circuit switched. In this study, we experimentally demonstrate an optically connected memory system in which a microprocessor accesses multiple 80-Gb/s memory modules all-optically across a hybrid packet- and circuit- switched optical network. Error-free communication between the microprocessor and main memory is confirmed (bit-error rates less than 10-12) with the optical network providing low-memory access latencies. The overall memory system reduces energy consumption by 28%.