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Resonator fiber optic gyro with bipolar digital Serrodyne Modulation Scheme

We have proposed and studied a resonator fiber optic gyro (R-FOG) with bipolar digital serrodyne phase modulation scheme. The serrodyne modulation serves multiple functions from reducing noises caused by fiber characteristics, such as backscattering and optical Kerr effect, to achieving gyro signal processing including closed-loop operation. Because the sensing fiber length in R-FOG is much shorter than that in interferometer FOG (I-FOG), the Shupe effect, which is caused by temporally variant temperature distribution along the fiber, can effectively be reduced in R-FOG. In this paper, a resonator made of a polarization-maintaining optical fiber (PMF) with twin 90o polarization-axis rotated splices has been proposed to suppress the polarization-fluctuation induced drift. An automated control to optimize the suppression has been proposed and demonstrated in experiments. To suppress the backscattering induced noise effectively, a precise adjustment of amplitude of the bipolar digital serrodyne waveform has also been introduced. Additionally, a closed-loop operation has been demonstrated by locking both the frequencies of clockwise (CW) and counter clockwise (CCW) travelling lightwaves to the resonator's resonant frequencies with manipulating the serrodyne waveform.