A closed loop fiber-optic gyroscope based on phase-locked loop

Fiber-optic gyroscopes are widespread sensors used in different fields, such as inertial navigation, seismology and positioning systems. In particular, for applications where high stability and dynamic range are necessary, FOGs are used in closed loop configuration. Here we show an all-electronic closed loop FOG based on a stand-alone phase-locked loop (PLL) system. This approach, is applied directly at the signal processing level without changing the existing optical setup. The PLL stabilizes the signal’s frequency reference and suppresses low-frequency fluctuations. A thorough analysis provides a characterization of the gyroscope’s performance which shows that this PLL-based technique remarkably reduce the residual noise at low frequency as well as improve the global stability of the system. The gyroscope shows a closed-loop residual noise in the range of 8 × 10^-6 – 2 × 10^-9 rad/s/√Hz over the frequency bandwidth 1mHz – 100 Hz. Future upgrades and perspectives are discussed.