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.

Abstract: To measure exactly minute elongations, for example on airplanes or bridge structures by means of a light wave conductor-phase sensor, the measuring beams of polarized light at the output of the sensor is divided by means of a beam divider into three partial light beams. The first partial light beam is directly received by a first light receiver; the second light beam is transmitted through a quarter wavelength plate and an analyzer to the second light receiver; and a third partial light beam is transmitted through an analyzer to the third light receiver. The electrical output signals from the light receivers carry information about extreme refraction values of the measuring light beam and are supplied to an electronic evaluation circuit.

Abstract: A device for measuring minute elongations of a light wave conductor is constructed as a light wave conductor-type sensing unit assembled of a series connection of a polarizer, a light coupler, a single polarization preserving, doubly refracting monomode light wave conductor enclosed in an elliptical sheathing and an analyzer. A light beam emitted from a laser diode is coupled via a light wave conducting correction cable to the polarizer and upon passage through the sensing unit is coupled via the light wave conducting connection cable to an optoelectric receiver and the electrical signals are evaluated in an electronic circuit. Changes in phase difference of the exiting light wave resulting from the minute changes in length of the light wave conductor are evaluated and scaled as geometric length units.

Abstract: A light wave conductor-sensor for tension, comprises a primary coated light wave conducting element, at least one coil wound on the primary light wave conducting element and forming together with the latter a sensor core, and a compound including longitudinally extending tension-proof fibers embedded in a synthetic plastic matrix, the compound forming a casing for the sensor core.

Abstract: A structural element is provided with at least one light conduit which is arranged thereon under a selected mechanical initial stress. In this manner, the deformation or breakage can be detected at loads or deformations which are lower than the breaking loads or deformations of the component parts to be monitored.

Abstract: A high tensile wire of a fiber-reinforced synthetic resin encloses an axially arranged light guide in the form of an optical fibers connectable to a light testing instrument. The light guide is enclosed in an intermediate sleeve of a heterogeneous synthetic material which is mechanically firmly connected both to the light guide and to the inner surface of the outer sleeve. In the preferred embodiment, the wire is used as a reinforcing span wire in concrete component parts and the attenuation of the light passing through the light guide indicates tensile strength, bending strength or breakage of the wire in the concrete.