Enhancing train transportation is a key issue as competing transportation means are gradually becoming saturated in capacity. The European Union (EU) tries to promote this by developing initiatives and enhancing the competitiveness of the rail grid by means of deregulation and interoperability, supporting this process with a planned upgrade to the existing rail network. The SMITS project (Smart Monitoring of Train Systems) of 5th European Framework Program (FP5) has been specifically devoted to control the contact force between the train pantograph and the Overhead Contact Line (OCL), enabling both the infrastructure managers to control the rolling stock operators compliance with their infrastructure rules (e.g.: pantograph maximum wear on the OCL), and the rolling stock operators to optimize the wear conditions and proceed to predictive maintenance. In such a context, several well-suited electromagnetic immune Optical Fibre Bragg Grating (FBG) sensor lines were integrated by SMITS partners into the current collectors, turning the pantograph into a 3 points bending-based sensor in direct contact with the OCL, offering the advantage to be less sensitive to inertial forces (especially those introduced by pantograph suspending devices), which should lead to more accurate measurements. A semi-empirical model, validated by FEM analysis and several laboratory tests performed at high voltages, was introduced into the signal processing software of a dedicated highly accurate and auto-calibrated FBG measurement system (accuracy and drift lower than 0.6 pm @ 1550 nm, and at 500 Hz measuring rate), providing simultaneous measurements over several FBG optical lines. On-line validation tests were performed during a full week on a very high speed train “TGV Duplex” between Paris and Vendôme (France) at speeds up to 320 km/h, leading to equivalent linear resolution better than 20 cm along the track. Contact forces between the pantograph and the OCL, as well as temperatures inside the current collectors were computed in real time at 500 Hz, on 4 lines in parallel, and immediately transmitted to the SNCF reference measurement system for comparison and validation. During these TGV tests, the innovative FBG measurement system developed by the CEA LIST has demonstrated its reliability and accuracy with temperature measurements, and coherence with contact force measurements in comparison with SNCF reference records.