Network planning strategies for next-generation flexible optical networks [invited]

Using well-established results on nonlinear propagation modeling in coherent optical links, two different approaches for network planning are addressed and compared in terms of performance maximization and robustness to dynamic changes in the network, one based on maximization of the margin in the optical signal-to-noise ratio, the other on minimization of the pre-forward-error-correction bit error rate (BER). We show that, in pure coherent optical networks, the planning strategy that best supports the dynamic evolution of the network is the design aimed at BER minimization. A closed-form formula for the maximum reach (in terms of number of spans and loss budget) of each interface is analytically derived, which is a useful tool for the evaluation of the overall network cost for a desired traffic capacity.