Ring interferometer with an arrangement to eliminate false indications

Claim 1

In a ring interferometer having a light source, at least one light sensitive surface of a detector, a light waveguide which is wound in the coil and has two ends, each end providing a separate coupling point at which light from the coherent source is coupled into the light waveguide and propagates to the opposite end for output coupling therefrom as output beams, said interferometer including means for receiving the output beams and directing portions thereof in a superimposed fashion to the light receiving surface, the improvements comprising means for reducing adulterating influences of undesirable interference light from reflected and back-scattered light components, said means for reducing including said light source being a pulsed light source producing a sequence of individual light pulses having a pulse duration (t) and an interval of time (T) between two consecutive light pulses, said pulse duration (t), said interval of time (T) and a predetermined length of the light waveguide between the coupling points being matched to one another so that the pulse duration (t) is smaller than the length of travel time required by the light to pass over the predetermined length of the light waveguide and the interval of time (T) between pulses is greater than said length of travel time, and said means for reducing including means for gating out a majority of the undesirable interference light at each detector.