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.