TIP-TILT CORRECTION WITH FAST REFRACTIVE MODULATOR IN A TELESCOPE

Nowadays, telecommunications are of fundamental importance in all areas, from work to simple leisure; however, there are still many areas that are not yet reached by good telecommunications and internet infrastructures. In particular the less supplied zones are outside the urban centers and rural areas. FSO communications are optical wireless communication which operates at the near Infrared frequencies and represents an alternative solution to underground fiber optics that could give the same type of connection to families or workplaces that are not necessarily located in large city centers. However this technology has some disadvantages like absorption and scattering by particles and atmospheric turbulence which affect the optical beam propagation along the FSO link in time-spatial domain. Adaptive optics, a system capable of correcting turbulence through the use of deformable elements, can be used FSO communication systems. In this case, since small apertures are used, it is sufficient to correct only for Tip and Tilt making the system even simpler and cheaper. This thesis work is focused on the development and tests of a refractive deformable element able to correct the beam for Tip and Tilt (Tip-Tilt Lens) in such a way that it can be easily integrated into an FSO telecommunications system to improve their performances; in particular bring a significant improvement on the fiber coupling efficiency. The experiment carried out in the laboratories of CNR-IFN, a 20 m FSO transmission of a collimated laser between two telescope mounts, is proposed.