Minimizing energy and cost in fixed-grid and flex-grid networks

Core networks offer high capacities, thanks mainly to the optical technologies they utilize, but they consume a non-negligible amount of energy. The traffic volume in metro and core networks is forecast to grow at very high rates, exceeding 30% per year for the next five years, and if the corresponding energy requirements grow analogously, they will sooner rather than later form a bottleneck for network communications. Thus, energy efficiency in optical networks is mandatory for the sustainability of the future Internet. The objectives of the current work are to identify the main causes of energy consumption for current fixed-grid wavelength division multiplexing and future flex-grid optical networks, and to propose and compare techniques for improving their energy efficiency. Toward this end, we carried out a comparative study of energy efficiency of flex-grid networks and fixed-grid single-line-rate and mixed-line-rate networks. Under realistic network scenarios, we calculated the energy consumption of the different components of the optical layer and demonstrated that by using energy-aware techniques in planning such networks, we can achieve significant power savings. Since energy prices are location dependent, especially in large networks, e.g., over continents, we show that accounting for such information can increase the cost savings.