Plasmonic modulators have been assessed for operation up to 200 GBaud in a turbulent 53 km free-space-optical link. They are shown to withstand space radiation and large temperature ranges making them ideal for space applications.

Highly efficient coherent beam combining (CBC) of two very-high-power optical amplifiers (VHPOA) with applications to long-range FSO communications such as ground-to-space feeder links is presented. The CBC setup is designed to minimize the telecom signal degradation, with a polarization beam splitter used to minimize the power fluctuations and to control the output polarization state of the beam. The system delivers 80 W output power and is proven to be compatible with 25 Gb/s telecom signals with a less than 1 dB power penalty.

Free space optical (FSO) links are considered as an essential part of future satellite communications as they benefit from wide optical bands, absence of frequency regulation, and synergy with terrestrial networks [1], [2]. Nevertheless, several challenges remain for enabling very high capacity optical links. For the optical feeder uplink, a major one is the generation of optical carriers strong enough to carry the communication signal from a ground station up to geostationary satellites. The output power of telecom optical amplifiers has been increased over the past decade, notably with the recent demonstration of very high power optical amplifier (VHPOA) capable of delivering up to 50 W [3]. However, the coherent beam combination (CBC) of several VHPOAs is a promising solution to meet the very demanding requirements of future optical ground-based terminals.

High power generation is an enabling technology for high capacity free space optical feeder links. We show the feasibility of optical transmission of WDM OOK / DPSK at high power based on 50 W amplifiers and their coherent combination to deliver up to 97 W power.

Optical feeder links (OFL) are expected to become part of future Very High Throughput Satellite (VHTS) systems in response to the growing demand for higher capacity and lower costs. H2020 VERTIGO (Very High Throughput Satellite Ground Optical Link) project was set to prove key optical communication technologies and to address: 1) Throughput increase with high spectral and power efficiencies. 2) Higher optical power generation and delivery. 3) Atmospheric turbulence mitigation by optical and digital processing. Transmit and receive optical communication models were developed in rack units for assessing, in laboratory and outdoor trials, their intrinsic performance, robustness against atmospheric turbulence and compatibility with other technologies. The models for 25 Gbps OOK/DPSK and RF analog modulation with optically pre-amplified direct or differential detection are reported with the achieved performance. An atmospheric channel emulator fed with time series established by simulations was used to mimic the propagation losses and fading of the optical signal coupled into the receiver. Both the downlink and uplink under weak or strong turbulence were emulated. For digital transmission experiments, the performance metrics include BER curves, detection sensitivity and power penalty. State-of-the-art sensitivities were achieved especially under 25 Gbps DPSK. For RF analog transmission, the performance metrics were constellation diagrams and Error Vector Magnitude (EVM) measured for various modulations from QPSK to 64-QAM. Are reported the results of optical transmission experiments first performed in the laboratory under static and dynamic propagation channels, then in the outdoor trial successfully carried out in July between Jungfraujoch and Zimmerwald in Switzerland.

A 1 Tbit/s 53km single channel free-space optical (FSO) link is demonstrated. High bandwidth, high order modulation formats and advanced adaptive optics are utilized. We show that the absence of a nonlinear-Shannon limit in combination with adaptive optics enables record data-transmission with low link failures.

Spontaneous capillary imbibition is a classical problem in interfacial fluid dynamics with a broad range of applications, from microfluidics to agriculture. Here we study the duration of the cross-over between an initial linear growth of the imbibition front to the diffusive-like growth limit of Washburn's law. We show that local-resistance sources, such as the inertial resistance and the friction caused by the advancing meniscus, always limit the motion of an imbibing front. Both effects give rise to a cross-over of the growth exponent between the linear and the diffusive-like regimes. We show how this cross-over is much longer than previously thought – even longer than the time it takes the liquid to fill the porous medium. Such slowly slowing-down dynamics is likely to cause similar long cross-over phenomena in processes governed by wetting.