This paper describes an ontology model (conceptual model) based on the ITU-T Recommendation G. 805 for transport network architectures. The goal is to take a step forward to the autonomic applications for transport network operation and management. Besides the conceptual model description and explanation, including its main elements (classes, properties and constraints), this paper also includes the description of the G. 805 recommendation main concepts characteristics. Furthermore, the paper elaborates on the advantages of using an ontological model, as well as the technologies used for ontology conceptual modelling and ontology implementation. Finally, this paper presents a case study using a simple OTN unidirectional network, in which automated inferences could be verified. In conclusion, the methodology and reference conceptual model of transport networks presented here constitutes a contribution towards autonomic network applications.