نبذة مختصرة : The growth of optical links in free space leads to systems with data rates of tens of gigabits/s. To reach such data rates, one of the most frequently considered approaches is to couple the received signal into an optical Single-Mode Fiber (SMF) and thus benefit from technologies developed for fiber links. However, due to atmospheric turbulence effects, a degradation of the coupling efficiency is present when the beam propagates in free space. Although turbulence mitigation techniques such as Adaptive Optics (AO) are widely used at high elevation angles, low-Earth orbit satellite-to-ground links have to deal with low elevation angles and longer propagation distance in the atmosphere. Such longer propagation induces intensity fluctuations which results in a more complex wavefront measurement. In this context, a new promising alternative to deformable mirrors is to decompose the perturbed wave into a set of propagation modes associated with different waveguides, and then coherently combining these guided modes. The mode decomposition is performed by a Space-Division Multiplexing (SDM) device. Once the received beam is decomposed into a set of modes, they are recombined through a Photonic Integrated Circuit (PIC). The advantages of this method include the absence of moving parts, its compactness, and its lower sensitivity to scintillation effects. This work is dedicated to the development of such a device. In the first part, an analytical approach is derived in order to describe the average effects of atmospheric turbulence when a beam is coupled with a set of propagation modes. Based on this analysis, the second part of this thesis is devoted to the coherent combination of different guided modes on a PIC. In the selection of materials for PICs, there is a trade-off between bandwidth, manufacturability and number of channels. The performance of this device in terms of overall power margin, as well as its statistical and temporal behavior through end-to-end simulations are considered. In this thesis, two different ...
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