The ever-increasing data rate demand for wireless systems is pushing the physical limits of standalone radiofrequency communications, thus fostering the blooming of novel high-capacity optical wireless solutions. This imminent penetration of optical communication technologies into the wireless domain opens up a set of novel opportunities for the development of a new generation of wireless systems providing unprecedented capacity. Unlocking the full potential of free-space optics (FSO) transmission can only be achieved through a seamless convergence between the optical fiber and optical wireless domains. This will allow taking advantage of the staggering progress that has been made on fiber-based communications during the last decades, namely leveraging on the latest generation of Terabit-capable coherent optical transceivers. On the other hand, the development of these high-capacity optical wireless systems still faces a set of critical challenges, namely regarding the impact of atmospheric turbulence and pointing errors. In this work, we provide an in-depth experimental analysis of the main potentialities and criticalities associated with the development of ultra-highcapacity FSO communications, ultimately leading to the longterm (48-hours) demonstration of a coherent FSO transmission system delivering more than 800 Gbps over ∼42 m link length, in an outdoor deployment exposed to time-varying turbulence and meteorological conditions.

Using an ANN channel estimator, we experimentally demonstrate an outdoor 400G FSO-link with slow-fading prediction and compensation. A transmission reliability of more than 99% is obtained after 3-hour BER measurements.

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With datacenters expanding their networks at a greater than ever rate, efficiently managing an extremely numerous a network of servers with high cabling complexity is a daunting task. This has motivated the rise of free-space optics (FSO) communication technologies, as a reliable new solution for high-capacity communication systems, which grants a possibility for the implementation of cable-free intra-datacenter communications as a way to reduce the level of network complexity. However, as the scientific community continuously explores FSO distinctive characteristics of unregulated large-bandwidth spectrum, to easily establish new communication links, atmospheric conditions threaten its commercial deployment. As such, the effects of atmospheric turbulence on FSO links have been under investigation by researchers from all over the world, leading to the proposal of several models in an attempt to predict and therefore mitigate the effects of adverse conditions. This study seeks to capture and analyze experimental data on the influence of turbulence on the received optical power of a FSO link in a controlled room, to simulate a datacenter environment, followed by the modeling of experimental data using the Log-Normal model. Using a small 2000 RPM Fan in three different positions we increased the atmospheric turbulence of the FSO channel and measured the differences in received optical power over the course of 1 hour per position. These measurements are then compared to a control obtained without externally induced turbulence. Using the obtained data, we demonstrate its Log-Normal fit, thus enabling to determine the Rytov variance for each scenario.