Closed-loop resonant fiber optic gyro with an improved digital serrodyne modulation

Abstract

To widen the linear dynamic range and improve the linearity, a closed-loop resonant fiber optic gyro (RFOG) is proposed and experimentally demonstrated. To overcome the effect of the imperfect serrodyne modulation, an improved frequency shifting module is designed and constructed on a LiNbO3 phase modulator. Its frequency resolution is improved to 0.01 Hz which is equivalent to a rotation rate of 0.04°/h for an RFOG with a 12-cm diameter fiber ring resonator. With the frequency shifter applied in the RFOG, a closed-loop detection is demonstrated, whose bias stability is around 2 °/h, close to that of the open-loop output. Moreover, good linearity and wide dynamic range are also experimentally demonstrated thanks to the closed-loop operation. The measured result shows that the open-loop linear detection range of ± 215°/s is improved to ± 1076°/s. It is improved by a factor of 5. The open-loop scale factor nonlinearity of 1.2% is decreased to 0.02% (200 ppm), which is improved by a factor of 60. These are the best results reported to date, to the best of our knowledge, for closed-loop RFOGs.

Resonator fiber optic gyro with high backscatter-error suppression using two independent phase-locked lasers

“…Figure 3 shows the residual parts per million deviations from a precalibrated lookup table for the gyro. This yields the effective scale factor linearity response at better than 25 ppm, which is the best known performance to date in an RFOG to our knowledge, and an 8x improvement over best previously reported results (13) . However, the measurement is primarily limited by bias offset drifts during the time it takes to complete one sequence, and therefore, an underestimate of the actual scale factor linearity.…”

A Hollow-Core Photonic-Crystal Fiber-Optic Gyroscope Based on a Parallel Double-Ring Resonator

“…The light emitted by the high-coherence laser is split into two equal-power beams (CW waves, CCW waves) by the LiNbO 3 Y-branch phase modulator (Y-PM), and modulated with the same modulation frequency f m . The phase modulator 1 (PM1) is driven by a serrodyne wave for frequency shifting and PM2 is used for the same purpose [24]. Then the CW and CCW waves enter two HCPCF ring resonators through a 2 × 2 coupler, where fiber ring resonator 1 (FRR1) transmits CW waves, while ring resonator 2 (FRR2) transmits the CCW waves.…”

Performance of closed-loop resonant micro-optic gyro with hybrid digital phase modulation

“…For a 125-MHz DAC, the reset time of the serrodyne wave can be ignored and the parameter X is thought as 1. Figure 3 shows the theoretical calculated sideband suppression [13] as a function of the phase amplitude at four different stair widths in the digital serrodyne wave. In the plots of Fig.…”