Ring interferometer with a multimode fiber waveguide

An expression is obtained for the output signal of a fiber ring interferometer with a multimode waveguide. It is shown that the precision of such an interferometer can be improved by the use of a light source characterized by a low spatial coherence. An analysis is made of the possibility of increasing the stability of the output signal by effective mode mixing at the input or in the multimode interferometer loop. The results are given of an experimental investigation of a prototype ring interferometer consisting entirely of a multimode fiber waveguide.