Ring interferometer with a mode diaphragm

Abstract

A ring interferometer, which has a coiled waveguide having two ends with each end being provided with means for coupling light from a first source into the waveguide and for uncoupling light coupled into the opposite end of the waveguide, a first optical arrangement for superimposing the uncoupled light from the two ends of the waveguide and forming two portions, an optical arrangement for directing one of the portions of the output coupled light at a first light receiving surface over a common path in a direction opposite to a direction of light from said first source characterized by a mode diaphragm being arranged in the common path to receive the one portion of the superimposed beam and the light from the first source to reduce the number of modes being transmitted therein. Preferably, a second mode diaphragm is arranged in the path of the other portion and both diaphragms are preferably a monomode waveguide such as an optical glass fiber having a core surrounded by a cladding. Preferably, the interferometer includes a second light receiving surface arranged to receive light coupled out of the second mode diaphragm. In an embodiment, a second light source is provided which may have a different wavelength than the wavelength of the first mentioned light source and filters are provided in the path of the light directed at each light receiving surface so that only light from the second source is received by the first receiving surface and only light from the first source is received by the second receiving surface.