Add and drop architectures for multi-carrier transponders in EONs

The elastic optical network (EON) is a paradigm for optical networks, based on the combination of a flexible grid, advanced transmission techniques, and bandwidth-variable optical switching. Recent studies on EONs have been focused on multi-carrier transponders with coherent detection. Such transponders can achieve high-rate (e.g., 1 Tb/s) lightpaths through super-channels. A particular case of the multi-carrier transponder is the sliceable bandwidth variable transponder (S-BVT) where the generated flows can also be routed onto different paths and toward different destinations. The add and drop (A&D) module connecting transponders to the optical cross connect plays an important role in the design of the network node. In particular, depending on the A&D architecture, the flexibility provided by the multi-carrier transponder and the S-BVTs may be partially limited. This paper gives first a technological overview of different A&D architectures. In particular, the coupler/splitter, multicast switch, and wavelength-selective switch technologies for A&D are reviewed. Then, we investigate how different A&D architectures influence the benefit of elastic spectral efficiency in a long-haul meshed network scenario, looking for a trade-off between costs and performance.