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Coherent Free-Space Optical Communications: Opportunities and Challenges

Guiomar, F. P. ; Fernandes, M. ; Nascimento, J. ; Rodrigues, V. ; Monteiro, P.

Journal of Lightwave Technology Vol. 40, Nº 10, pp. 3173 - 3186, May, 2022.

ISSN (print): 0733-8724
ISSN (online):

Scimago Journal Ranking: 1,45 (in 2018)

Digital Object Identifier: 10.1109/JLT.2022.3164736

Abstract
The ever-increasing data rate demand for wireless systems is pushing the physical limits of standalone radio-frequency 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-high-capacity FSO communications, ultimately leading to the long-term (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.