Triple closed-loop resonant micro-optical gyroscope based on optoelectronic hybrid feedback

Abstract

The resonant micro optical gyro (RMOG) is considered to be a unique type of optical gyroscope with great application prospects because of its high precision and miniaturization. However, high precision RMOG systems are generally required to have the narrow full width at half maximum (FWHM) of the resonance spectrum. The dynamic range of the open-loop detection method based on FWHM demodulation output is correspondingly narrowed. Therefore, we propose a triple closed-loop control system based on optoelectronic hybrid feedback in this work. First, the sawtooth wave feedback loop is used to the track the angular velocity, which reduces the influence of the nonlinear error and improves the dynamic range of the system. Second, the laser frequency locking loop (LFLL) achieves frequency locking by locking the laser's output frequency at the static resonance frequency of the waveguide ring resonance. Third, the light intensity feedback loop is introduced to reduce the optical Kerr noise by minimizing the light intensity difference between the clockwise (CW) and counterclockwise (CCW) directions. Experimental results show that, when using this method, the dynamic range of the gyroscope system is increased from AE686°∕s to AE5365°∕s compared with the open-loop output detection scheme, which is eight times higher. The light intensity difference between the CW and CCW channels decreases from 7.91 to 0.615 mV. The backscattering noise width under dual phase modulation technology decreases from 9.2 to 0.76 mV. The nonreciprocal noises, mainly optical Kerr noise and backscattering noise, is reduced by about one order of magnitude. The long-term bias stability measurement of the RMOG system is 0.926 °/h.