Pantograph-Catenary interaction constitutes the fundamental sliding mechanism able to feed the train engine with the electrical power necessary to its motion. To maintain this mechanical coupling in well-functioning conditions, it is valuable to have a good and specific monitoring system able to evaluate the contact force magnitude and position. Systems available nowadays for this purpose are characterized by a limit to the measuring frequency range up to 20 Hz due to a rigid collector assumption. The objective of this paper is the definition of an alternative method for contact force estimation able to extend the measuring frequency range. The solution found consider fiber Bragg gratings strain optical sensors placed along the pantograph collector. The developing of the system is presented starting from the optical setup. The results obtained adopting two different data treatments strategies are analyzed and commented.