Abstract: A measuring device with a light wave conductor-bending sensor for monitoring bridge structures comprises a light emitter and a light receiver, a multi-mode light wave conductor arranged to extend along a structural part and having two ends connected with the light emitter and the light receiver, respectively, an elongated plate having a lower side arranged to be placed on and connected with the structural part and also having an upper side provided with a longitudinal groove, two sliding rails arranged in the longitudinal groove and having outer ends fixed to the plate and inner ends spaced from one another to form an intermediate space and movable relative to the plate. The light wave conductor is fixed with one of the sliding rails, then extends through the intermediate space and forms a freely movable curve, and then exztends along and is fixed to the other of the movable rails.

Abstract: To enable a continuous measurement of damping of a light beam in light wave conductor (LWC)-sensor which is accessible at one end only, a measuring light beam emitted by a transmitter is guided through a light wave conductor into a beam divider in which a measuring partial light beam is guided in the same direction as the transmitted beam to a measuring LWC-sensor. At the free end of the sensor the measuring partial light beam is totally reflected to propagate in reverse direction back against the beam divider where it is deflected by 90.degree. and guided into a light receiving and measuring unit. The other partial light beam is employed either for the temperature compensation or for the compensation of the power output of the light transmitter or of sensitivity of the light receiver.