Fig. 1. Schematic of closed-loop fiber optic gyroscope with electrical cross-coupling

Fig. 2. Working principle diagrams of four-state modulation when 0≤φf<φ0. (a) Variation of output signal for gyro rotation; (b) variation of output signal of gyro with change in half-wave voltage

Fig. 3. Working principle diagrams of four-state modulation when φ0≤φf<2π-φ0. (a) Variation of output signal with gyro rotation; (b) variation of gyro output signal with change in half-wave voltage

Fig. 4. Working principle diagrams of four-state modulation when 2π-φ0≤φf<2π. (a) Variation of output signal with gyro rotation; (b) variation of gyro output signal with change in half-wave voltage

Fig. 5. Simulation images of feedback phase. (a) Not in dead zone; (b) in dead zone

Fig. 6. Schematic of analog adding feedback method

Fig. 7. Fiber optic gyroscope prototype platform

Fig. 8. Gyro output curve of four-state modulation method

Fig. 9. Partial experimental results of feedback phase. (a) Not in dead zone; (b) in dead zone

Fig. 10. Gyro output curve of analog adding feedback method

Fig. 11. Gyro output curve of ratio four-state demodulation method