Disaggregation at the optical layer is expected to bring benefits to network operators by enriching the offering of available solutions and enabling the deployment of optical nodes that better fit their needs. In this paper, we assume a partially disaggregated model with transponder nodes for transmission and ROADMs for switching, where each optical node is conceived as a whitebox consisting of a set of optical devices and a local node controller that exposes a single interface to the software-defined networks (SDN) controller. An architecture to provide autonomic networking is proposed, including the SDN controller and supporting monitoring and data analytics capabilities; YANG data models and software interfaces have been specifically tailored to deal with the level of disaggregation desired. To demonstrate the concept of autonomic networking, use cases for provisioning and self-tuning based on the monitoring of optical spectrum have been proposed and experimentally assessed in a distributed test-bed connecting laboratories in Spain and Italy.