Discrete Model of Backscattering Drift in Fiber Optic Gyroscopes

We present a new model of backscattering drift in a fiber-optic gyroscope (FOG) using square-wave modulation and demodulation and interrogated with light of arbitrary lineshape and linewidth. By modeling the effect of the linewidth on the drift via a coherence function, the convergence and computation time of numerical simulations of the drift at broad linewidths is significantly improved. Numerical solutions show that for square-wave modulation and demodulation, the drift has no dependence on coil length and a steep dependence on linewidth Δν at broad linewidths (Δν
^-1.5
). A simple single-scatterer model is presented to explain these dependencies physically, and to show that the different dependencies on the coil length and linewidth predicted by previous models are solely due to the different modulation and/or demodulation waveforms used in these models. This article also shows that the backscattering drift can be reduced by using sine-wave demodulation and a Lorentzian-lineshape source.