Performance analysis of QoT estimator in SDN-controlled ROADM networks

While new SDN control planes promise to provide faster and more dynamic provisioning of optical paths, mis-estimation of optical signal to noise ratio (OSNR) is still an issue that reduces the amount of capacity available in practice to allocate data paths. Typically, additional margins are applied to the estimation of OSNR for given paths, however, in the absence of detailed knowledge on the gain function of EDFAs, these margins are applied equally to all paths, leading to network under-utilisation. In this paper we show this effect over a simulated optical network based on the Telefonica Spanish national topology, emphasising the reduction in capacity due to the incomplete knowledge the network controller has on the exact wavelength and time based variation of EDFA amplifiers gain. We consider this to be of high relevance, as it opens up the road for further experimentation on the use of sparse optical performance monitoring to provide data that can be used to improve the QoT estimation from the control plane of an SDN-based system. The simulation used is based on the Mininet framework. This provides the advantage of testing SDN control planes that can be then utilised on experimental ROADM networks. In order to link SDN controller and the Mininet Emulation environment, we have developed an optical agent capable of simulating the behaviour of ROADMs systems.