A Highly Adaptive and Energy-Efficient Optical Interconnect for On-Board Server Communications

As the global IP traffic and its demand for computation increase in a rapid and sustained manner, processor, server, and network architectures are also undergoing a considerable evolution. Two of the manifestations of this evolution are the integration of a large number of computing nodes in a single server and the interconnection of many servers via high-speed communication links. At present, however, the node-to-node communication bandwidth is one of the severest resource bottlenecks in massively parallelized applications. There is a concerted effort by the academia and the industry to achieve higher data rate by assembling multiple parallel links. This effort, however, is inherently limited by many constrains, including space. Optical interconnects, on the other hand, promise superior data rates, lower transmission losses, and less inter-channel crosstalk when compared to electrical interconnects. Development in this area promise data rates in the range of Tera bits per second per link and beyond. So far, however, little attention is given to the power adaptiveness of optical interconnects. In this paper, we present an optical interconnect concept which adjusts its power consumption in response to the change in the statistics of the incoming workload. The several components of the link have been designed and developed in hardware. Based on initial power and performance measurements of the components, a link model of our optical interconnect was created. The performance-power consumption characteristics of this model was simulated applying different workload statistics and the potential of the energy savings by the adaptivity have been evaluated. It is revealed that the power consumption of our optical interconnect reduces by up to 40% when its workload was exponentially distributed (signifying underutilisation) compared to a Weibull distribution workload (signifying full capacity workload). This study confirms the high potential for power saving in performance adaptive optical interconnects.