Method and arrangement for the measurement of rotations by the sagnac

Abstract

In order to permit the measurement of very small rotation rates, the rotan rates are measured by the Sagnac effect in a light path encircling an area. To accomplish this, two coherent light beams are coupled into the two ends of said light path of which a section is subject to perturbations that affect the polarizations of said two light beams. After the beams emerge again from the ends of said fiber, they are superimposed so that they interfere. The rotation rate of said light path can then be evaluated from an analysis of the interference. In particular, in order to reduce sensitivity to the perturbations, the two light beams are coupled with defined states of polarization into said light path of which a section is subject to perturbations, and the two interfering beams pass through at least one polarization analyzer, the azimuth and ellipticity of which is adjusted for maximum transmission of light which is the conjugate of one of said light beams coupled into said light path at one end thereof. An automatic control system, responding to variations of polarization, is used to maintain a stable state of polarization of at least one of said two light beams emerging from said perturbed section of said light path, said stable state of polarization being distinctly different from that state which is blocked by said polarization-analyzer.