As ROADMs manufacturing process evolved, it became possible to build optical switching nodes that are colorless, directionless and contentionless. These types of switching nodes increase significantly the possibilities of setting up new optical paths, allowing new connectivity services to be offered, such as transport network topology virtualization. One solution to deal with the higher complexity in control operations in such scenario is the SDN architecture, which allows the inclusion of new control features by means of "network applications". This paper presents one use-case of such applications in a SDN scenario by using a PCE capable of doing physical layer impairment analysis, such as total OSNR estimation.