Abstract: Assembly comprising: a set of strands that extends in a direction of tension in which the set of strands is intended to experience tensile stresses; at least one diagnostic fiber that is integrated into the set of strands and able to conduct light, the light propagating through the diagnostic fiber between an entrance end and an exit end, that extends in the direction of tension, and that has a mechanical tensile strength close to that of one of the strands; and a diagnostic device comprising a light source for sending a light beam into the diagnostic fiber via the entrance end, a first optical sensor for delivering a signal representative of the light intensity at the exit end of the diagnostic fiber, the light intensity at the exit end of the diagnostic fiber being correlated to the mechanical state of the diagnostic fiber.