Energy efficient Traffic-Aware design of on–off Multi-Layer translucent optical networks

Abstract

Efficiency in energy consumption is attracting greater and greater attention in recent years to the point that it is becoming one of the major constraints steering the evolution of our society. In addition to developing new low-consumption devices, one can further reduce the power consumption of optical networks by allowing IP and WDM layer units (racks, shelves, line cards, transponders (TXPs), regenerators) to be jointly switched on/off “following” the daily variation of traffic demand.In order to evaluate the benefits of such on/off strategies, in this study we first propose an accurate model of power consumption and housing constraints of both IP and WDM layers of an IP-over-WDM translucent optical network architecture. Second, we present a Traffic-Aware design technique (i.e., network design allowing reconfiguration when traffic varies) as a Mixed Integer Linear Programming (MILP) formulation based on an extended version of the so-called “connectivity graph”. Third, we evaluate the impact on power consumption of Multi-Layer network architectures when coherent and non-coherent transmission technologies are employed. Fourth, we analyze the energy savings arising from switching on/off devices jointly at IP and WDM layers when traffic demand changes. We show that the contribution of the WDM layer to the power consumption is about 10% of the overall network consumption regardless the employed transmission technology and the type of traffic. We demonstrate that in Multi-Layer networks and for current traffic needs, coherent transmissions do not exploit their extended reach and they show the worst performance in terms of energy consumption although they represent a future-proof technique to cope with the expected increase of traffic over long distances. Finally, we present our Traffic-Aware design results on Multi-Layer translucent networks showing that we can save on average up to almost 50% of the peak-traffic power consumption.