Thermal phase noise in giant interferometric fiber optic gyroscopes

The thermal phase noise in giant interferometric fiber optic gyroscopes (fiber length L > 10 km) and its impact on the detection sensitivity are theoretically derived and experimentally verified. It is confirmed that thermal phase noise cannot be overlooked for the giant IFOGs. Utilizing high order eigen frequency modulation can effectively suppress the walk-off component of thermal phase noise, but the residual part contributes to high-frequency range thus limits the detection bandwidth of giant IFOGs. The self-noise is experimentally demonstrated as 3.5 nrad/s/Hz at low frequencies and 5.2 nrad/s/Hz at 100 Hz in the IFOG with a 30-km single mode fiber coil. Discussions about the fiber characteristics on thermal phase noise are presented, which paves the way to the design of giant IFOGs.