Silicon Photonic Interconnects: Minimizing the Controller Latency

Silicon photonic interconnects (SPIs) have emerged as a promising solution to outperform the communication infrastructure in multiprocessor systems-on-chip (MPSoCs). Routing a message from one node to another in an MPSoC integrating SPIs, several photonic components (e.g., switching elements) need to be configured to realize an optical path between sending and receiving nodes. Such configurations are performed in an electronic controller, which, if not fast, imposes high latency in SPIs, constraining the application of SPIs in MPSoCs. Realizing a full exploitation of SPIs, this paper presents a look-up-table-based centralized controller (LUCC). We indicate that LUCC has the lowest latency among the state-of-the-art controllers for SPIs while it can be applied to different SPI architectures. Employing acceleration techniques based on off-line routings, we report (simulation and prototyping) a worst-case control latency smaller than 5 ns. Moreover, LUCC is experimentally integrated with a photonic switch in the lab, where we show contention resolution in one clock cycle.