  Multi-mode fibers (MMFs) and single-mode fibers (SMFs) are widely used in
optical communication networks. MMFs are the practical choice in terms of cost
in applications that require short distances. Beyond that, SMFs are necessary
because of the modal dispersion in MMFs. Here, we present a method capable of
interfacing an MMF with an SMF using a re-programmable multi-plane light
conversion scheme (MPLC). We demonstrate that only 3-phase modulations are
necessary to achieve MMF-to-SMF coupling efficiencies from 30\% to 70\% for
MMF's with core diameters up to 200 microns. We show how the obtained coupling
efficiency can be recovered if the output field of the MMF changes entirely,
e.g. through strong deformation of the fiber, by simple monitoring of the
field. Furthermore, we test the influence of the resolution of both essential
devices (field reconstruction and MPLC) on coupling efficiencies. We find that
commercially available devices with increased speed and efficiency, such as
wavefront sensors and deformable mirrors, are sufficient for establishing an
MMF to SMF interface which auto-corrects any decoupling in the kHz regime.
