Theory of a novel high sensitivity optical fibre gyroscope

A novel optical fibre gyroscope, with a structure making use of the combination of a Sagnac interferometer with an active fibre ring-resonator, is proposed and analysed. It can be regarded as a generalised structure of the conventional Sagnac interferometric fibre optic gyroscope (SIFOG). Counter-propagating optical waves in the gyroscope can circulate many times in the sensing loop into which an optical amplifier is incorporated to compensate partially for optical losses of each circulation. The optical response is effectively the sum of the optical responses of a series of conventional Sagnac interferometric fibre optic gyroscopes having effective loop length equal to the fibre loop length multiplied by the number of circulations. We show that the sensitivity of the proposed gyroscope can be two orders of magnitude higher than that for a conventional SIFOG and that the minimum detectable nonreciprocal phase shift limited by the amplifier noise is nearly one order of magnitude smaller than that of conventional SIFOG limited by quantum noise. These performance enhancements cannot be obtained by incorporating an optical amplifier into the conventional SIFOG structure.