We developed a new optical network (ON) simulator that aims to take into account the physical layer impairments and eventually handle future optical functionalities (OFs) in a generic way. The tool is designed to accurately evaluate the Quality of Transmission (QoT), by modelling precisely the physical degradations affecting the transmitted signals. The QoT encompasses the physical impairments and is used in the routing and wavelength assignment (RWA) decision making at the network level. Preliminary results show the impact of an accurate evaluation of the physical impairments on the traffic blocking probability compared to results obtained without the QoT input. In addition, we give a practical example on how our simulator is able to integrate wavelength conversion, a well-known OF, and evaluate its impact on the network performance. This opens the perspective to add new OFs and propose a wider range of use cases.