On the Routing and Scalability of MZI-based Optical Beneš Interconnects

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Silicon Photonic interconnects are a promising technology for scaling computing
systems into the exa-scale domain. However, there exist significant challenges
in terms of optical losses and complexity. In this work, we evaluate the applicability of a thermally/electrically tuned Beneš network based on Mach-Zehnder Interferometers for on-chip and inter-chip interconnects as regards its scalability.
We examine how insertion loss, laser power and switching energy consumption
scale with the number of endpoints. In addition, we propose a set of hardware inspired routing strategies that leverage the inherent asymmetry present in the
switching components. We evaluate a range of network sizes, from 16 up to 256
endpoints, using 8 realistic and synthetic workloads and found very promising
results. Our routing strategies offer a reduction in path-dependent insertion
loss of up to 35% in the best case, as well as a laser power reduction of 31% for
32 endpoints. In addition, bit-switching energy is reduced by between 8% and
15% using the most efficient routing strategy, depending on the communication
workload. We also show that workload execution time can be reduced with
the best strategies by 5-25% in some workloads, while the worst-case increases
are at most 3%. Using our routing strategies, we show that under the examined technology parameters, a 32-endpoint interconnect can be considered for
the NoC domain in terms of insertion loss and laser power, even when using
conservative parameters for the modulator.

Bibliographical metadata

Original languageEnglish
JournalNano Communication Networks
Publication statusAccepted/In press - 10 Oct 2020