Theory of an amplified closed-Sagnac-loop interferometric fiber optic gyroscope

An Amplified Closed-Sagnac Loop Interferometric Fiber Optic Gyroscope (AC-IFOG) has been proposed. It is constructed from an open-loop interferometric fiber-optic gyroscope with an erbium-doped fiber amplifier (EDFA) that closes the sensing coil into a re-entrant configuration. Earlier experiments have shown a 6.56 fold increase in rotation response factor at a rate of 5 degrees over a conventional gyroscope using the same fiber length and light source. This paper reports the theoretical analysis of its operation. The analysis has been focused on the effect of the EDFA inserted within the re-entrant path. The analysis shows that the rotation detection factor can be increased by at least two orders as compared to a conventional IFOG when the EDFA is an ideal device. A mathematical expression for the open-loop response has been derived and it agrees well with the experiment result.