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Based on second harmonic difference between two counter-propagating beams, a harmonic subtraction technique is proposed to suppress the intensity modulation induced Kerr effect drift in a closed-loop RFOG. The linear relationship between Kerr effect induced drift and second harmonic difference is established, and based on this relationship, the harmonic subtraction algorithm is proposed. The intensity modulation induced Kerr effect drift is tested in the practical closed-loop RFOG, and it is found that the intensity modulation does cause a significant Kerr effect drift, which becomes larger as the initial second harmonic difference increases. The tests for gyro output signal are carried out with harmonic subtraction technique to verify its effectiveness. It is indicated that this technique could achieve a noise suppression ratio of better than 7.95%. It is concluded that the harmonic subtraction technique really works in suppressing the intensity modulation induced Kerr effect drift in a closed-loop RFOG. [ABSTRACT FROM AUTHOR]

Aiming at the demodulation signal compensation technique for intensity modulation noise suppressing in a digital RFOG, which is based on the detection of closed loop’s second-harmonic, the quantization precision for second-harmonic is discussed and optimized. By analyzing second-harmonic’s fluctuation under the intensity modulation noise equal to shot noise limited sensitivity, the expression for the required minimum quantization bits of second-harmonic signal is obtained. Based on this expression, numerical simulations are carried out to optimize the quantization bits in a digital RFOG in detail. Based on over-sampling technique, the stability of gyro output signal with different quantization bits and rotation rates is tested to verify the theoretically analyzed results. It is concluded that the minimum quantization bits of second-harmonic is related to the rotation rate and the ratio of second-harmonic’s maximum to minimum, and it gets larger as these two parameters are increased. Especially, the required minimum quantization bits for second-harmonic would generally exceed that supported only by hardware circuits, which leads to the adoption of over-sampling technique. And it is proven that the quantization precision improvement for second-harmonic, realized by the over-sampling technique, does work in improving the effect of intensity modulation noise suppressing. [ABSTRACT FROM AUTHOR]