Dimensioning optical WDM backbone networks with mixed line rates

As new Internet applications are emerging, traffic in optical backbone networks is increasing with heterogeneity in bandwidth and QoS requirements. Higher bit-rate wavelength channels of 40 Gbps, 100 Gbps, and beyond are being deployed in WDM backbone networks to meet these growing traffic needs. Mixed-line-rate (MLR) networks that support various line rates on the same fiber are becoming popular to address the heterogeneous traffic growth. We study the important problem of long-term cost-effective dimensioning of WDM backbone networks with MLR. Our study should enable operators to dimension their networks with deployment of MLR transponders and optical cross-connect (OXC) ports over multiple time periods. We study two multi-period dimensioning approaches: all-periods planning and incremental planning. Our approaches predict the network equipment to be deployed at various nodes in the network during each time period while exploiting the cost reduction of network equipment over time to support traffic growth over multiple time periods. We propose mixed-inter-linear-program (MILP) solutions and a computationally-efficient heuristic. Our illustrative examples show that significant cost savings can be achieved by our long-term planning approaches.