Low-Drift Fiber-Optic Gyroscope Interrogated With Multiple Broadened Semiconductor Lasers

We achieved the best performance reported so far for a laser-driven fiber-optic gyroscope (FOG), namely a measured angular random walk (ARW) of
${\rm{320\ \mu deg/}}\sqrt{\mathrm{h}} $
, a bias drift of 5.7 mdeg/h, and a mean-wavelength stability less than 0.5 ppm. This performance meets the inertial-grade requirement for transcontinental airliners, and it is superior to the performance of an SFS-driven FOG in terms of ARW and mean-wavelength stability. This result was achieved by probing the FOG's 3-km Sagnac interferometer with low-coherence light from four lasers broadened by the same noise-driven phase modulator. This approach is shown to further reduce the temporal coherence compared to a single broadened laser. Optical gating was also applied to suppress the residual drift due to the Kerr effect. Models are presented to quantify the noise and drift and their dependencies on the number of lasers and the gate's duty cycle, and to estimate the mean-wavelength stability. Experimental results agree well with the prediction that the noise and drift decrease in inverse proportion to the square root of the number of lasers, and with the predicted mean-wavelength stability. This technique can be easily extended to a larger number of lasers to further reduce the drift while maintaining a mean-wavelength stability of less than 1 ppm.