PODCA: A Passive Optical Data Center Network Architecture

Abstract

Optical interconnects have gained great attention recently as a promising solution offering high throughput, low latency, scalability, and reduced energy consumption compared to electrical interconnects. However, some active optical components, such as tunable wavelength converters and micro-electro-mechanical systems (MEMS) switches, suffer from high cost or slow reconfiguration times, and have been roadblocks to the realization of all-optical interconnects. In this paper, we propose three versions of a passive optical data center network architecture (PODCA), depending on the size of the network. Our key device is the arrayed waveguide grating router (AWGR), a passive device that can achieve contention resolution in the wavelength domain. In our architectures, optical signals are transmitted from fast tunable transmitters; pass through couplers, AWGRs, and demultiplexers; and are received by wide-band receivers. Our architecture can scale to over 2 million servers. Simulation results indicate that PODCA exhibits lower latency and higher throughput even at high-input loads compared with electrical data center networks such as Fat-Tree and Flattened Butterfly, and comparable performance with other optical interconnects such as DOS and Petabit, but at much lower cost and power consumption. The packet latency of PODCA in our simulation experiments is below 19 μs, and the throughput is 100%. Furthermore, we compare the power consumption and capital expenditure (CapEx) cost of PODCA with the other four architectures. Results show that PODCA can save at least 75% on power consumption and 50% on CapEx.