Open-Loop Experiments in a Resonator Fiber-Optic Gyro Using Digital Triangle Wave Phase Modulation

Analysis of Kerr effect in resonator fiber optic gyros with triangular wave phase modulation

“…Figure 3 shows the calculated demodulation curve near Δf RES ¼ 0 of the R-FOG for an air-core PBF sensing loop. The modulation frequency of the CW beam is fixed to F M CW ¼ 62:5 kHz [17,18], while the modulation frequency for the CCW beam takes three different values of F M CCW ¼ 62:5 kHz, 60 kHz, and 70 kHz. The output intensity I 0 of the fiber laser is assumed to be 1 mW, and the center frequency and the spectral linewidth of the laser are f 0 ≈ 1:9 × 10 14 Hz and δf ¼ 60 kHz, respectively [16]; the fiber length L of the FRR is 20 m [19], the effective refractive index n r of the PBF is 0.99, the mode filled area A is 4:42 × 10 −11 m 2 , and the impedance Z is 380.53 [15]; the Kerr coefficient can be expressed as [13] …”

“…The CW signal is demodulated by the demodulation circuit DMC1, and the demodulated signal is used to lock the center frequency of the fiber laser to the CW resonance of the FRR through the feedback circuit FBC. The CCW signal is demodulated by the demodulation circuit DMC2, and the demodulated signal is proportional to the rotation rate [16,17]. Figure 2 shows the waveform of the triangular wave phase modulation signal φ t CW for the CW beam, where F M CW is the modulation frequency, and the phase modulation index is fixed to π rad [16].…”

“…And the Kerr effects in the R-FOGs with square-wave frequency modulation [14] and sinusoidal phase modulation [5,15] have been analyzed previously. We here analyze the effect of Kerr nonlinearity on the performance of an R-FOG with triangular phase modulation [16,17] for both the clockwise (CW) and the counterclockwise (CCW) propagating waves, and we evaluate the performance improvement by use of air-core PBF instead of a conventional SMF sensing loop. We focused here our analysis on the triangular phase modulation since it is better in reducing backscatter induced noise as compared to sinusoidal phase modulation [16].…”

“…We focused here our analysis on the triangular phase modulation since it is better in reducing backscatter induced noise as compared to sinusoidal phase modulation [16]. We present a general formulation on the effect of Kerr nonlinearity for an R-FOG based on triangular wave phase modulation [16,17], and we provide an expression for the demodulation curve when the Kerr effect is considered. Numerical simulations are then carried out for R-FOGs with air-core PBF and conventional SMF respectively as the sensing loops.…”

“…The performance of R-FOGs with air-core air-silica PBF and conventional SMF sensing coils are compared. Figure 1 illustrates the system configuration of the air-core PBF R-FOG based on the triangular wave phase modulation [16,17]. The fiber ring resonator (FRR) can be made entirely from conventional SMF or from air-core PBF spliced to the two arms of a conventional SMF coupler C4.…”