Near shot-noise limited performance of an open loop laser-driven interferometric fiber optic gyroscope

Abstract

We report for the first time experimental evidence of near shot-noise limited performance for an open loop interferometric fiber optic gyroscope interrogated with a narrowband laser instead of a broadband source. Using a highly coherent laser source (Δf = 2.2 kHz), the measured gyroscope noise is 350 nrad/√Hz for an average returning power of 20 μW, while the measured noise for the same gyro operated with a broadband source (Δλ ≈ 30 nm) was 850 nrad/√Hz. This measured noise is only ~2 dB above the calculated shot noise for this power. This result was made possible by using a very narrow linewidth, which greatly reduces the laser phase noise and thus the phase-noise-mitigated coherent backscattering. This excellent noise performance has applications for future fiber gyroscope technologies as well as other sensors utilizing a Sagnac interferometer. The bias drift of the laser-driven gyroscope was higher than anticipated but could be reduced to roughly Earth-rate using a frequency sweeping technique. In addition to improved sensitivity, the benefits of using a laser include much higher scale factor stability, lower power consumption, and lower component cost.

Low-Drift Closed-Loop Fiber Optic Gyroscope of High Scale Factor Stability Driven by Laser With External Phase Modulation

“…where 0 E is the constant amplitude of the laser field, and τ is the random fluctuation time of the phase. The broadened spectrum with 0 v as the central frequency can be obtained by calculating the Fourier transform of (9). By increasing the PSD of the GWN under the same bandwidth, the spectrum asymptotically becomes a smooth Gaussian with the broader linewidth and less optical carrier as shown in Fig.…”

“…From the perspective of market, the IFOG has a tendency to replace the RLG completely. However, the most serious problem needing to solve in this process is to improve the scale factor stability of the IFOG, which is usually driven by the broadband superluminescent diode (SLD) or superfluorescent fiber source (SFS) and its average wavelength stability is much worse than that of laser [9].…”