Super-channel spectrum saving optimization procedure in elastic optical networks

Optical networks have historically been overprovisioned for physical-layer conditions and capacity and, as such, operate uninterrupted over several years. By reducing system margins, network efficiency and cost savings could be improved without compromising network reliability. On the other hand, super-channel transmission has been identified as a suitable solution for supporting high-data-rate connectivity. NETCONF, along with YANG models, has been recognized as a software defined networking (SDN) configuration and management protocol enabling control in a vendor-neutral way. Moreover, the OpenConfig YANG model defines vendor-specific transmission parameters, such as modulation format and bit rate, within operational modes. This paper investigates the trade-off between super-channel quality of transmission (QoT) and spectrum saving by allowing slight subcarrier overlap and tight filtering, hence reducing system margins. An automatic spectrum-efficient super-channel optimization procedure is experimentally demonstrated using a 600 Gbit/s transponder in an SDN-controlled elastic optical network. The automatic procedure performs the adaptation of filter bandwidth and subcarrier spacing. The latter is effectively operated by transponder agents, without involving the SDN controller, thus reducing the margins while guaranteeing that the QoT enables savings of up to 25% of the spectrum.