Exploiting spectrum sharing for soft failure recovery

Elastic optical networks (EONs) offer several optimization dimensions that can be harvested to increase network efficiency and survivability. More specifically, the adaptation of the modulation format to a more robust one can recover the quality of transmission (QoT) of a lightpath affected by a soft failure (i.e., a physical layer degradation resulting in QoT deterioration). In this scenario, increasing the robustness of a transmission may require a spectrum increase. Thus, the spectrum also might have to be reconfigured. In this paper, we propose spectrum sharing between lightpaths of classes requiring different rate guarantees. In the case of a soft failure, a high-priority, rate-guaranteed lightpath can expand its spectrum to recover its QoT at the expense of spectrum allocated to a lower-priority, guaranteed minimum rate lightpath. We propose an integer linear programming (ILP) routing and spectrum assignment (RSA) algorithm for the planning phase and an online RSA for the operation phase of the network that optimize spectrum sharing among lightpaths of different classes. Using these proposed techniques can effectively reduce the network costs to guarantee the rate of high-priority connections.