Sensitivity characterization of in-fiber acousto-optic interaction

Abstract

In this work we present the broadband characterization of in-fiber acousto-optic interaction in fiber SM2000 (Thorlabs), with a special focus on the sensitivity of the technique as a measurement tool of the parameters of the fiber. The acoustooptic interaction technique provides good sensitivity when measuring parameters of singlemode or few-mode fibers: dispersion curves, radius, or core refractive indices (both linear and nonlinear) can be determined by means of this tool with accuracy. The basics of the technique rely on its resonant character: as a parameter of the fiber changes, the optical wavelength that fulfills the acousto-optic phase-matching condition shifts. The measurement of the acousto-optic phase matching curve provides information about the sensitivity of the technique as a function of variations of different parameters of the fiber. Such measurements can be performed in a broadband spectral range, using a single section of fiber of some tens of cm. In this paper, we report the measurement in detail of the acousto-optic dispersion curves for the couplings LP01-LP1,1-4, in the optical range 1.0-2.0 μm. From these data, we characterize the sensitivity of the technique for the measurement of the core radius, external radius and numerical aperture of the fiber, especially around the turning point of the phase-matching curve for the acousto-optic coupling.