An interferometer with single-mode optical waveguide wound in a coil which waveguide has a surface at each end for the acceptance of light into the waveguide and for the display of light in the waveguide characterized by at least one polarizing filter being arranged in the path of light emerging from each end surface of the waveguide. Preferably, the interferometer includes a light source such as a laser, at least one beam dividing element which is arranged in the path of a light beam and a coupling arrangement for coupling the light of one of the partial beams into one of the end surfaces and the other partial beam into the other end surface. While the interferometer utilizes a device for detecting the superimposed images of the light exiting both end surfaces of the waveguide, preferably two devices are utilized which can be either a screen or a light sensitive element such as a photo diode.