Optical packet switch with energy-efficient hybrid optical/electronic buffering for data center and HPC networks

Advanced optical switching architectures, capable of scaling to thousands of ports while achieving low communication latency and reduced power consumption, are becoming a dominant theme for interconnection networks in next-generation data centers and high-performance computing systems. The arrayed waveguide grating (AWG) device, with its inherent ability to perform wavelength routing of many wavelengths in parallel, has been recognized as a promising core component for fast optical switching. Although the AWG is energy efficient (as essentially a passive optical device), has high-bandwidth switching capabilities and has relative simplicity and low cost, an inherent characteristic of switching schemes based on the AWG is potential wavelength oversubscription at switch output ports, which can lead to high packet blocking probabilities. To resolve this traffic congestion, this paper proposes a hybrid optical/electronic buffering scheme and a method for efficiently integrating fiber delay line buffer capacity into the AWG wavelength assignment scheme. The dimensioning of the optical and electronic buffer resources is then carried out using simulations. The results indicate that with the proper dimensioning, the hybrid-buffered AWG switch achieves significantly increased overall energy efficiency, compared to electronic-only buffering, while maintaining low latency and non-blocking performance. We also investigate the computational complexity of the required scheduling algorithm in the hybrid-buffered switch, which in turn allows us to estimate the required processing power of the switch controller.