Benjamin, J; Gerard, T; Lavery, D; Bayvel, P; Zervas, G; (2020) PULSE: Optical Circuit Switched Data Center Architecture Operating at Nanosecond Timescales. Journal of Lightwave Technology , 38 (18) pp. 4906-4921. 10.1109/JLT.2020.2997664.

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Abstract

We introduce PULSE, a sub-μs optical circuit switched data centre network architecture controlled by distributed hardware schedulers. PULSE is a flat architecture that uses parallel passive coupler-based broadcast and select networks. We employ a novel transceiver architecture, for dynamic wavelength-timeslot selection, to achieve a reconfiguration time down to O(100 ps), establishing timeslots of O(10 ns). A novel scheduling algorithm that has a clock period of 2.3 ns performs multiple iterations to maximize throughput, wavelength usage and reduce latency, enhancing the overall performance. In order to scale, the single-hop PULSE architecture uses sub-networks that are disjoint by using multiple transceivers for each node in 64 node racks. At the reconfiguration circuit duration (epoch = 120 ns), the scheduling algorithm is shown to achieve up to 93% throughput and 100% wavelength usage of 64 wavelengths, incurring an average latency that ranges from 0.7-1.2 μs with best-case 0.4 μs median and 5 μs tail latency, limited by the timeslot (20 ns) and epoch size (120 ns). We show how the 4096-node PULSE architecture allows up to 260 k optical channels to be re-used across sub-networks achieving a capacity of 25.6 Pbps with an energy consumption of 82 pJ/bit when using coherent receiver.

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