Exploiting Classes of Services to Mitigate the Impact of Fading in Free Space Optics Links for Satellite Networks

In future Free Space Optics (FSO) high-speed links between Earth and satellites, we will use the available transceivers designed for fiber-optics networks. Deep fading events due to FSO propagation can dramatically impact network performance and have an even greater effect because of receivers designed for a stable power. Here, we investigate these effects in an experimental testbed, where we emulate the effect of a single fading event with variable depths, and measured its impact on the receivers. We observe significant different tolerance in a 10 Gbit/s OOK and in a 100 Gbit/s DP-QPSK commercial Optical Transport Network (OTN) transceivers. The results show quite dissimilar impact and largely different recovery times; this allows us to introduce a reliability scheme at network level that assumes two classes of service (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gold</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">best-effort</i>), corresponding to 10 Gbit/s and 100 Gbit/s transmission, respectively. The proposed solution is experimentally validated in the lab, confirming a remarkable reduction of lost packets of gold traffic. This approach, combined also with other fading mitigation techniques, could be a feasible option for future FSO networks, with various classes of service.