Benefits of unidirectional design based on decoupled transmitters and receivers in tackling traffic asymmetry for elastic optical networks

We consider a unidirectional design approach to tackle the traffic asymmetry in an elastic optical network (EON). We decouple a bidirectional transponder into a pair of separate unidirectional transmitters and unidirectional receivers, and consider different multi-flow transmitters that use either an array of laser diodes or a broadband laser source with filters to generate multiple sub-carriers. To evaluate the benefit of this unidirectional design, we have considered the routing and spectrum allocation optimization problem for the EON. An integer linear programming model and an efficient heuristic algorithm based on spectrum window planes have been developed. Simulation results show that the proposed unidirectional design approach can significantly improve capacity utilization and minimize network cost compared to one based on bidirectional symmetric traffic flows. It is also efficient for network scenarios with spatial traffic asymmetry and where multi-period network planning is required.