Increasing the capacity of optical networks raises the issue of cost optimal bitrate migration into existing infrastructures. In this paper, we use the migration from 10G to 40G services as an example. 10G demands can be groomed into 40G channels or transmitted natively, reducing reach of concurrently mixed 40G channels. We study the migration scenario from a networking point of view, optimizing the migration strategy in terms of capital expenditures. For a lower and an upper cost bound, we apply the two multiperiod planning approaches: all-periods planning and incremental planning, respectively. The migration optimization shows considerable impact from forecast knowledge to cost optimality, channel mix, and aggregation decisions. The impact of the topology dimension on migration strategy and overall costs are investigated for a USA and a British network. For long-term migration under traffic growth, optimal network cost is achieved by early investments in 40G-only equipment—a conclusion that applies to both network topologies.
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