Software-defined elastic optical network node supporting spectrum defragmentation

The elastic optical network (EON) benefits from improved spectrum utilization, but also faces new challenges in resource allocation. The spectrum continuity and contiguity constraints in routing and spectrum allocation can cause spectrum fragmentation, which would increase traffic blocking. In this paper, we present an EON node structure supporting spectrum defragmentation and a novel software-defined networking (SDN)-based control scheme to resolve the fragmentation problem. In the proposed node, bulk traffic can be spectrally separated and fit into multiple fragments. This way, fragmentationinduced traffic blocking can be mitigated intelligently. Moreover, the SDN control scheme features effective physical-layer abstraction, which is compatible with different defragmentation implementations. We experimentally demonstrate the software-defined EON node on a laboratorial test-bed. Four-wave-mixing-based spectrum multicasting is applied to implement defragmentation, and the corresponding operation procedure of the node Agent is presented. The captured controlling messages and measured signal performance confirm the effectiveness of the solution.