Observation of the Sagnac effect in a ring resonant interferometer with a low-coherence light source

A fibre-optic resonant ring interferometer with a low-coherent light source was investigated experimentally. The feasibility of measuring the parameters of ring cavities characterised by very narrow lines (of the order of tens of kilohertz) was demonstrated by using a broad-band light source and a retroreflecting Doppler mirror. The Sagnac effect was first observed in a ring resonant interferometer with a low-coherence light source. Modulation and compensation of the phase nonrecriprocity in a low-coherence resonant interferometer with the aid of an optical frequency shifter located outside a sensing fibre loop were observed experimentally.