Characterization and Exploitation of the Rotational Memory Effect in Multimode Fibers

Abstract

In an ideal perfectly straight multimode fiber with a circular core, the symmetry ensures that rotating the input wave front leads to a corresponding rotation of the output wave front. This invariant property, known as the rotational memory effect (RME), remains independent of the typically unknown output profile. The RME thus offers significant potential for imaging and telecommunication applications. However, in real-life fibers, this effect is degraded by intrinsic imperfections and external perturbations, and is challenging to observe because of its acute sensitivity to misalignments and aberrations in the optical setup. Building on a previously established method for precisely estimating fiber transmission properties, we demonstrate an accurate extraction of RME properties. Additionally, we introduce a comprehensive theoretical framework for both qualitative and quantitative analysis, which specifically links the angular-dependent correlation of the RME to the core deformation’s geometrical properties and the fiber’s mode characteristics. Our theoretical predictions align well with experimental data and simulations for various amounts of fiber distorsion. Finally, we demonstrate the ability to engineer wave fronts with significantly enhanced correlation across all rotation angles. This work enables accurate characterization of distributed disorder from the fabrication process and facilitates calibration-free imaging in multimode fibers.