Abstract: A system for locating Fresnel reflections along an optical fiber, including an emission circuit for emitting optical pulses which are coupled into the input face of the fiber; a reception and transformation circuit (20) for receiving signals reflected by the fiber and transforming them into electrical signals; a selection circuit (20) for taking the electrical signals and selecting therefrom only those electrical signals which correspond to Fresnel reflections; a comparison circuit (23, 25, 26) coupled to the selection circuit (20) and receiving a comparison reference signal expressing the rank of an arbitrarily-chosen one of the Fresnel reflections; and an evaluation circuit (13, 21, 22, 24, 26) coupled to the comparison circuit (23,25,26) and to the selection circuit (20) so as to locate the point along the fiber that gave rise to the arbitrarily-chosen Fresnel reflection.