Optical Network Control Exploiting Open Interfaces

The exponential growth of internet data traffic necessitates a significant evolution in network infrastructure, particularly within optical networks. Modern optical networks are increasingly incorporating software-based devices designed to enhance the management and optimization of data traffic. These devices include transponders, which are responsible for injecting signals at fixed frequencies, and Reconfigurable Add Drop Multiplexers (ROADM), which play a crucial role in managing signal forwarding within the network. Each of these devices operates with specific hardware and runs its own operating system. The passage from static hardware devices to software-based ones represents a critical aspect towards the evolution to the open optical Software Defined Networks (SDN). An open optical SDN is characterized by a disaggregated network structure controlled by a central software-based entity known as the SDN controller. The SDN controller is designed to manage the reconfigurable devices, by sending towards them specific commands for data exchange. Before moving towards the proposed activities, it is important to focus on the ROADM entity, analyzing both hardware and software aspects, since it plays a key role in the experiment. ROADMs are devices that enable the dynamic reconfiguration on the handling of the optical signal's forwarding. The principal aspects studied are the architecture of the ROADM and the signal's handling, focusing in particular on how to create the software entities aimed to route the incoming signals, dividing them in channels according to the Wavelength Division Multiplexing (WDM) rules, to equalize the created channels and to retrieve information of each channel's power. Typically, networks are oriented towards single-vendor solutions: in particular the devices belong to the same model. A transition to multi-vendor scenario is possible with the transition towards the open optical SDN, and can offer significant advantages: multi-vendor networks enable cost control through diverse market options, allowing for the selection of various device models. The diversification of the devices introduces also a competitive scenario, able to enhance the models. To move towards a multi-vendor scenario, it is necessary to develop standard models to ensure interoperability within a multi-vendor network. In this context, the interoperability between the controller and a specific ROADM model has been tested to demonstrate the feasibility of multi-vendor communication. This test illustrated how communication happens between the controller, utilizing a specific standard, and a ROADM device with its proprietary language. In particular, there is an interaction between ONOS, an open source optical SDN controller that runs inside the laboratory, and the Adtran model of ROADM, always present in the lab: the selected standard is OpenROADM, whose aim is the control of the ROADMs. To handle the OpenROADM requests, a driver has been developed and its aim is the conversion of the commands, originally written according to the OpenROADM standard, to the proprietary language supported by the Adtran model. The driver has been written in C-language and collects the most important functions for the ROADM management, related to the creation of optical paths and forwarding of incoming signals.