An improved device for measuring the contact force between a contact wire and a power collector in an electrically powered vehicle, specially an electrical railway vehicle, by use of optical fiber force sensors. To this end, two compact force sensors are arranged between the base body (7) of the contact strip (6) and the pantograph rocker frame (5) or between the wearing element or shoe (8) and the base body (7) of the contact strip (6). Each sensor includes a deformable body (11), which is elastic in an axial direction but highly rigid crosswise, with the body being fitted with an integrated optical fuber reflex sensor (19). Axial deformations of the deformable body (11) equivalent to the contact force are detected by the reflex sensor (19) with high resolution, accuracy and no interference, are then signaled to a device (27) via optical fibers requiring no potential and converted therein into contact force-equivalent signals (28) or instructions (29).