Robust Design of Spectrum-Efficient Green Optical Backbone Networks

We propose an orthogonal frequency division multiplexing (OFDM) based optical network design focussing on minimizing the total power consumption of the network to make the network green. OFDM is a promising technology for next-generation optical networks to support high capacity and heterogeneity in network traffic by having flexible bandwidth allocation per wavelength. Another paradigm for supporting traffic heterogeneity and high bandwidth demands is mixed-line-rate (MLR) networks where wavelengths can have discrete capacities of 10/40/100 Gbps which are single carrier based. In this study, we compare the energy efficiency of an OFDM-based network versus a MLR network. We formulate mixed integer linear program (MILP) models to design energy-efficient MLR and OFDM-based networks with two scenarios: (1) with fixed average traffic per source-destination pair of the network, and (2) with uncertainties in the traffic that an actual network may have. For scenario (2), we employ a robust optimization technique which is called Gamma-robust optimization. Our results show that OFDM outperforms MLR in terms of energy efficiency especially when the traffic in the network takes random peaks in some of the links.