Dedicated protection with signal overlap in elastic optical networks

In optical dedicated path protection (1+1), the same optical signal is transmitted along both working and backup paths. Thus, in 1+1, the transmission parameters need to be configured according to the most impaired path, e.g., the backup one. This implies that the working signal is typically served with higher than necessary quality of transmission and occupies larger than necessary spectrum resources, leading to inefficient network resource utilization. In this study, we propose to apply the recently introduced signal overlap technique to improve network efficiency of optical dedicated path protection. The signal overlap technique enables uncorrelated optical signals to be superimposed along the same spectrum resources. It relies on a cancellation detection strategy also exploited in wireless communications and recently applied on coherent optical receivers. In particular, this study summarizes the key aspect and transmission performance of the overlap technique and discusses its implementation complexity. Then, two signal overlap schemes, namely, working signal overlap and working and backup signal overlap are introduced for effective optical dedicated path protection. An integer linear programming (ILP) formulation based on the routing, modulation, and spectrum allocation problem and an efficient heuristic are then presented to effectively assess the performance of the proposed overlap-based 1+1 protection strategy under various topologies and traffic profiles. In the considered simulative scenarios (e.g., network diameters well below a thousand kilometers), results show that the more efficient working and backup signal overlap scheme significantly improves the accepted load of dedicated protection requests.