Simultaneous Suppression of Thermal Phase Noise and Relative Intensity Noise in a Fiber-Optic Gyroscope

The short-term sensitivity of a several-kilometers long fiber-optic gyroscope (FOG) is limited mainly by thermal phase noise (TPN) and relative intensity (RIN). Increasing the modulation frequency decreases TPN but not RIN since it behaves as white noise. Here, we propose experimentally demonstrate that angular random walk (ARW) can be effectively decreased suppressing at its third-order harmonic using direct feedback to drive current superluminescent diode (SLD). Our simultaneous suppression yields an ARW 15 $\mu {\text {deg}}/\sqrt {{\text {h}}}$ bias instability 33 {deg}}/{\text {h}}$ fiber coil with length 5 km effective area 280 notation="LaTeX">${\text {m}}^{{{2}}}$ for measurement time 40 h.