Energy-efficiency of all-optical transport through time-driven switching

Decreasing the Internet power consumption is a challenging issue. Optical transport networks employing the wavelength division multiplexing (WDM) technique have been identified as energy efficient solutions to face this issue, considering the expected high increase of Internet traffic. The authors study the energy efficiency of a recently-proposed switching technique for transport networks, the time-driven-switching (TDS), in which time-coordination of network elements is exploited to achieve 'sub-lambda' granularity in optical signal switching directly in the optical domain. In order to achieve the fast switching time required by TDS, semi-conductor optical amplifier-based optical switches are exploited. The authors discuss the properties, in terms of the energy efficiency, of a TDS transport network, focusing on the energy requirements of the TDS optical switches. The authors provide a qualitative description of the main contributors to energy consumption in a TDS network. The authors then develop an integer linear programming formulation, in which the physical impairments impact over optical signals is also considered. Power consumption over realistic case study networks for the TDS case is compared to the power consumption for the classical IP over WDM architecture, and in some cases TDS is demonstrated to save more than 55% of power consumption with respect to competing architectures.