System to optically detect the actuation of the brake in a vehicle.

The system has a detection device (7) placed on or in a rear wall (51) of a braking assistance servomotor (5) and comprising a LED (70) emitting a light beam towards an inner skirt (3) of the servomotor. The device has a photodetector (71) to detect light reflected by the skirt. The LED is oriented such that the beam is reflected by the skirt towards active surface of the photodetector when the servomotor is at rest.