A harmonic subtraction technique to suppress intensity modulation induced Kerr effect drift in a closed-loop RFOG

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.