Energy Efficient and Energy Proportional Optical Interconnects for Multi-Core Processors: Driving the Need for On-Chip Sources

Silicon photonics is the prime candidate technology to realize an optical network-on-chip for global interconnects in future multi-core processors. Since silicon photonics lacks efficient native-substrate optical sources, the question is whether off-chip or heterogeneously integrated on-chip sources are the preferred technology. In this paper we argue, based on arguments of energy efficiency and energy proportionality, that on-chip sources provide a dramatic overall system efficiency improvement, as compared to using an off-chip (comb) source. We estimate an increase in source efficiency for on-chip lasers of close to 20 dB. These results provide a clear case to include on-chip lasers, such as hybrid silicon lasers, into the network architecture design.