Avoiding signal distortion in several classes of dynamic fiber-optic interrogators

Dynamic fiber-optic interrogators, which employ frequency scanning to determine measurand-induced frequency shifts (as in fiber Bragg Gratings (FBGs) and Brillouin-based interrogations), normally report their measurement results on a uniform time grid. In reality, these instruments find their reported frequency shifts on a non-uniform time grid. The resulting errors, mainly harmonic distortion and nonlinear response, are shown to increase to severe levels as the sampling rate approaches the Nyquist criterion and as the employed frequency-scanning span comes close to the measurand dynamic range. Guidelines are provided how to estimate these errors and how to choose an operating point that minimizes these distortions.