Fiber optic gyroscope interrogated with three multiplexed broadened semiconductor lasers

We report the best noise and drift ever achieved by a laser-driven FOG, namely an angular random walk of 368 μdeg/√h and a drift of 6.66 mdeg/h. This improvement was achieved by interrogating the 3-km Sagnac interferometer of the FOG with a low-coherence light source consisting of three lasers broadened by the same noise-driven phase modulator, which further reduces the temporal coherence compared to a single broadened laser. Proper optical gating is also applied to suppress the residual drift due to the Kerr effect. The experimental results agree well with our prediction that both the noise and the drift improve as the square root of the number of lasers. Using multiple lasers also improves the mean-wavelength stability of the light source compared to a single laser. Thanks to the low cost of semiconductor lasers, this technique is a promising and cost-effective solution that can be easily extended to a larger number of lasers for further reduction of the noise and drift in high-accuracy FOGs.