The European Commission promotes initiatives enhancing rail grid competitiveness through a planned upgrade of train transportation network. In such a context, the Smart Monitoring In Train Systems (SMITS) European project is devoted to control contact forces between pantographs and Overhead Contact Lines (OCL), enabling infrastructure managers to control the rolling stock and to optimize the predictive maintenance. Optical Fibre Bragg Gratings (FBGs) sensors were integrated into current collectors, turning pantographs into 3-point bending-based sensors in contact with the OCL. A semi-empirical model was introduced into the software of an innovative self-calibrated dedicated measurement system, providing accurate data at 500 Hz over several FBG optical lines. On-track tests were performed on a “TGV Duplex” train at speeds up to 320 km/h. Contact forces, and temperatures inside the collectors were computed in real time, on 4 optical fibers. During these runs, the FBG measurement system has demonstrated its reliability and accuracy with temperature measurements, and coherence with contact force in comparison with reference records provided by the SNCF.