Patent ID: 8922779

Claim:
A method comprising: generating a plurality of harmonic demodulation signals based on a detection signal of an open-loop fiber-optic gyroscope and a phase modulator signal of the open-loop fiber-optic gyroscope, the plurality of harmonic demodulation signals including a first harmonic demodulation signal and a second harmonic demodulation signal, wherein the first harmonic demodulation signal and the second harmonic demodulation signal are substantially synchronous; generating a delayed first harmonic demodulation signal by adding a delay time period to the first harmonic demodulation signal; generating a delayed second harmonic demodulation signal by adding the delay time period to the second harmonic demodulation signal; generating a first multiplied signal by multiplying the first harmonic demodulation signal and the delayed first harmonic demodulation signal; generating a second multiplied signal by multiplying the first harmonic demodulation signal and the delayed second harmonic demodulation signal; generating a third multiplied signal by multiplying the second harmonic demodulation signal and the delayed second harmonic demodulation signal; generating a fourth multiplied signal by multiplying the second harmonic demodulation signal and the delayed first harmonic demodulation signal; generating a first combined signal by subtracting the fourth combined signal from the second combined signal; generating a second combined signal by adding the first multiplied signal and the third multiplied signal; generating a divided signal by dividing the first combined signal by the second combined signal; and generating a Sagnac phase shift measurement value by adding a previous Sagnac phase shift measurement value and the divided signal filtered by a first low pass filter; wherein the time gap between the Sagnac phase shift measurement value and the previous Sagnac phase shift measurement value is substantially equal to the delay time period.