Angular-Random-Walk Reduction for Fiber Optic Gyroscopes Using Light-Intensity Switching

Raising the detected light intensity is fundamentally important for reducing the angular-random-walk (ARW) coefficient, which stands for the total output noise, of the fiber optic gyroscope (FOG). Conventionally, the transition spikes, which are unavoidably generated in the modulated optical output, easily reach the saturation level in photodetection, thus preventing the detected intensity from being increased. In this work, we propose the technique of light-intensity switching, which is implemented by a Mach-Zehnder-interferometer based intensity modulator. By synchronizing the switching-off periods with the predictable presence of intensity spikes, valid information is preserved in the optical signal while photodetection is sheltered from the consequences of intensity spiking. Besides, a closed-loop scheme is designed for compensating the errors of the intensity modulator in practice, including the half-wave-voltage variation and the operating-point drift. With this approach, the maximum detectable intensity is no longer limited by the intensity-spike saturation but by the source output power instead. Experimentally, we obtain 37.50% less ARW with 3.57 times more detected intensity than the maximum one in the conventional case. This technique provides a feasible route for improving the FOG measurement accuracy without modifying the fiber-coil dimension, and contributes to simplifying down-line electronic processing and avoiding deleterious effects related to intensity spiking like the rotation-rate measurement error due to the pulse-decay instabilities.