THEORY OF A NOVEL HIGH-SENSITIVITY OPTICAL-FIBER GYROSCOPE

A novel optical fibre gyroscope, with a structure making use of the co mbination of a Sagnac interferometer with an active fibre ring-resonat or, is proposed and analysed. It can be regarded as a generalised stru cture of the conventional Sagnac interferometric fibre optic gyroscope (SIFOG). Counter-propagating optical waves in the gyroscope can circu late many times in the sensing loop into which an optical amplifier is incorporated to compensate partially for optical losses of each circu lation. The optical response is effectively the sum of the optical res ponses 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 sensitivit y of the proposed gyroscope can be two orders of magnitude higher than that for a conventional SIFOG and that the minimum detectable nonreci procal phase shift limited by the amplifier noise is nearly one order of magnitude smaller than that of conventional SIFOG limited by quantu m noise. These performance enhancements cannot be obtained by incorpor ating an optical amplifier into the conventional SIFOG structure.