Fundamental Limits on Energy Use in Optical Networks

Fundamental energy limits in communication systems are reviewed and applied to a gedanken network model in order to determine the corresponding ideal minimum energy requirements on classical, non-adiabatic, uniform-demand optical networks. Introduction Recent focus has been placed on information and communication technologies (ICT) as a means to achieve greater efficiency in applications as diverse as indoor climate controls, automobile traffic coordination, and the electric power grid. So-called 'smart' technologies utilize ICT for energy efficient monitoring and control. At the same time, concerns have been raised that ICT equipment efficiency improvements may be lagging network traffic growth rates. Recent studies indicate that dramatic improvements in network energy efficiency will be required to sustain current growth trends. This need quickly raises the question of how far the efficiency can be increased or equivalently what are the limits to the energy per bit required in communications. Determining global energy limits is complicated because of the diverse technologies, constraints, and topologies used in communication networks. This complexity is similar to the situation for integrated circuits. A chip in itself is a network of transistors. Some understanding of energy limits in such complex systems can be derived by considering a 1 hierarchy of technological limitations . Starting from fundamental physical constraints, different limits can be built up as layers of complexity are added: material limits, device limits, circuit limits, and chip limits.