| 摘要 |
A closed loop fiber optic rotation sensing system prevents the occurrence of instabilities in its feedback signal by modulating the counterpropagating waves with a reference signal and demodulating an electrical signal indicative of the phase difference of two counterpropagating waves with the reference signal. The modulating means is driven to null the phase difference between the counterpropagating waves, and the feedback signal is adjusted to prevent instability. The counterpropagating waves may be either phase modulated or shifted in frequency. The means for modulating the counterpropagating waves may comprise a fiber optic frequency shifter connected to the fiber optic sensing coil and means for applying the reference signal to the frequency shifter. The feedback signal is adjusted with either a pseudo-random or a periodic signal having a zero mean value to prevent instability.
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