Field Trial of SDN-Controlled Probabilistic Constellation Shaping Supporting Multiple Rates Over a Coupled-Core Multi-Core Fiber

Space division multiplexing (SDM) is being investigated in support of traffic growth. SDM networks offer multiplexing over space and spectrum dimensions. Probabilistic constellation shaping (PCS) is a solution to optimize spectral efficiency by adapting the constellation of a M-ary quadrature amplitude modulated (QAM) signal to physical layer impairments. At the control plane, in the recent years NETCONF and YANG have been identified as the protocol and the data modeling language, respectively, for the configuration and management of network devices. Significant effort has also been directed to network disaggregation and vendor neutrality: an example is the work done within the OpenConfig consortium. In this article, we present a SDM field trial based on a deployed coupled-core four-core fiber, where a software-defined network (SDN) controller configures probabilistic constellation shaping through NETCONF, by optimizing spectral efficiency either with respect to the path length, or in response to degradations due to soft failures. The NETCONF protocol relies on the OpenConfig YANG data model to configure and manage transceivers. In the field trial the integrated data and control planes are demonstrated with multiple rates (800-850-900-950-1000 Gb/s) for optical reach values ranging from 910 km to 2730 km. Soft failures are also introduced and a characterization of their impact on transmission performance is provided in order to design the recovery strategy deployed by SDN controller. Indeed, depending on the changes in the electrical signal-to-noise ratio, the SDN controller reconfigures the constellation shaping to restore the optical connection affected by the failure with a reduced line rate.