SRing: A Sub-Ring Construction Method for Application-Specific Wavelength-Routed Optical NoCs

Wavelength-routed optical networks-on-chip (WR-ONoCs) attract ever-increasing attention for supporting high-speed communications with low power and latency. Among all WRONoC routers, optical ring routers attract much interest for their simple structures. However, current designs of ring routers have overlooked the customization problem: when adapting to applications that have specific communication requirements, current designs suffer high propagation loss caused by long worst-case signal paths and high splitter usage in power distribution networks (PDN). To address those problems, we propose a novel customization method to generate application-specific ring routers with multiple sub-rings, SRing. Instead of sequentially connecting all nodes in a large ring, we cluster the nodes and connect them with sub-ring waveguides to reduce the path length. Besides, we propose a mixed integer linear programming model for wavelength assignment to reduce the number of PDN splitters. We compare SRing to three state-of-the-art ring router design methods for six applications. Experimental results show that SRing can greatly reduce the length of the longest signal path, the worst-case insertion loss, and the number of splitters in the PDN, significantly improving the power efficiency.