Study on the Output Signal Modulation for Laser Gyro with Mechanical Dither Bias

Abstract

The amplitude of the output signal of prisms laser gyro with mechanical dither bias is always modulated. Theoretical analysis and experimental research on the ray trajectories, assembly situation and polarized properties of light were carried out. Results show that during the dither bias, the light transmitting route deviation caused by stress induced birefringence of prisms and the relative displacement between the photodetector and output light spot was the main reason responsible for the modulation. Polarized experiment data demonstrated that when the value of polarized power of output light below the 25.5% of that in ideal static situation, the standard error over 0.0337dBm, and the displacement extent of prism is higher than the 53% of radius of the beam waist in gyro cavity, the amplitude modulation extent of gyro output signal would be up to 16%, which badly influences measurement precision of laser gyro. Using the symmetric structure for laser gyro design, adopting prisms material with a suitable refractive index and reducing the photodetector deviation could reduce the extent of output signal's amplitude modulation obviously.