Multi-band elastic optical network (MB-EON) is a promising technology to extend the bandwidth of the current elastic optical networks in the middle term. The migration from current networks to MB-EONs should be made carefully taking into account both the required cost and the bandwidth requirements. This paper focuses on the necessity of looking for a trade-off between the links to be upgraded during the migration from the standard C-band to the L-band and the acceptable level of capacity increase. Therefore, it makes two contributions to efficiently upgrade current elastic optical networks: firstly, a planning method to decide which fibers should be upgraded to exploit C+L band; and second, one heuristic for solving the routing, band, modulation level, and spectrum assignment (RBMLSA) problem during network operation. Simulation results demonstrate that, thanks to use of these proposals, the upgrade of a set of the fibers could be viewed as a fully convincing middle term solution by the network operators to get around the huge cost of the whole network migration to C+L line system.

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Space division multiplexing (SDM) and band division multiplexing (BDM) are considered promising technologies to increase the capacity of optical transport networks. The progressive shortage of available dark fibers and the immaturity of multicore and multimode fibers for multichannel transmission induce network operators to postpone the process of capacity enhancement through SDM. Therefore, capacity increase revolves around BDM by lighting up at least the L-band of the already installed optical fiber infrastructure, which is a practical solution in the short to middle term. However, L-band activation requires the upgrade of network components such as erbium-doped fiber amplifiers (EDFAs). To manage the imposed cost while leveraging the L-band, a network can be partially rather than fully migrated in a single step by upgrading just a subset of the fibers and thus a subset of EDFAs to operate in the C+L-bands. In this paper, the focus is set on determining which fibers in the network should be upgraded to exploit the L-band, subject to a constraint on the maximum number of EDFAs to be upgraded, and analyzing its impact on network performance when facing dynamic traffic in terms of the blocking ratio. To this end, three heuristic algorithms, each pursuing a different objective, and two of them based on an integer linear programming (ILP) formulation, are proposed for the network planning to identify which fibers to upgrade. Simulation results demonstrate that, thanks to the use of these heuristics, the upgrade of a partial set of links to the C+L line system is a viable solution for network operators to circumvent the huge cost associated with migrating the full network. For instance, we demonstrate that a strategic partial upgrade using the proposed methods, subject to upgrading a maximum of 60% of the EDFAs, can significantly boost the supported traffic load in the examined topologies, ranging from 175% to 322%, when compared to the non-upgraded network.

A novel protection mechanism for C+L multi-band optical networks is introduced. It provides two levels of protection based on service level agreement (SLA) differentiation. We demonstrate that this technique can reduce the request blocking ratio for all SLAs.