Closed-loop resonant fiber optic gyro with an improved digital serrodyne modulation

Area of Science:

• Photonics and Optical Sensing
• Inertial Navigation Systems

Background:

• Resonant fiber optic gyros (RFOGs) are crucial for rotation sensing.
• Existing RFOGs face limitations in linear dynamic range and linearity due to modulation imperfections.

Purpose of the Study:

• To develop and demonstrate a closed-loop RFOG with enhanced linear dynamic range and linearity.
• To overcome limitations of serrodyne modulation in RFOGs.

Main Methods:

• Proposed and experimentally demonstrated a closed-loop resonant fiber optic gyro (RFOG).
• Designed and constructed an improved frequency shifting module using a LiNbO3 phase modulator to address imperfect serrodyne modulation.
• Implemented closed-loop detection with the improved frequency shifter.

Main Results:

• Achieved a frequency resolution of 0.01 Hz (0.04°/h for a 12-cm fiber ring resonator).
• Demonstrated a bias stability of approximately 2 °/h.
• Significantly improved the linear detection range from ±215°/s to ±1076°/s (a factor of 5).
• Reduced scale factor nonlinearity from 1.2% to 0.02% (200 ppm) (a factor of 60).

Conclusions:

• The closed-loop RFOG design successfully widens the linear dynamic range and improves linearity.
• The enhanced frequency shifting module effectively mitigates modulation imperfections.
• The achieved performance represents state-of-the-art results for closed-loop RFOGs.