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To overcome data rate limitations of RF communication links with satellites, TNO and Airbus Netherlands envision optical free-space communication feeder links for next generation high throughput satellites. This poster presents a feasibility assessment of such links and the technology needed by means of a link budget and a turbulence model of terabit/s optical links. Based on these parameters, requirements and status of the link-subsystems are discussed, and a roadmap is presented, aimed at achieving terabit per second optical feeder links.

Multiple groups world wide are currently developing laser communication terminals for downlinking data from satellites in the LEO orbit directly to earth in the so call DTE (Direct To Earth) configuration. These terminals will require a network of ground stations to downlink their data. The challenge for the communication industry is the following: - as no CCSDS standard is defined yet and currently different space terminal architectures are being developed (wavelength, no channels, Modulation and coding formats, and protocols) meaning that interoperability will be challenging. Therefore a single station that can serve all will be of high value. - There is a ‘Chicken-Egg’ situation where customers will likely not invest in space terminals until there is an operational OGS network capable of downlinking the data from satellites and the OGS network will be not implemented until there is a strong pull from the market to do so. TNO and its partners recognize this issue and are actively working to break this deadlock.

To support the development program on Optical Communication (OC), a dedicated facility for testing is being realized. Such a facility will be used for technology development and to perform end to end communication tests. The facility aims to enable the following three high level functionalities: testing of critical technologies and subsystems in a laboratory setting ; execution of end to end Ground to Ground (G2G) laser communication testing between two field stations placed at few kilometres distance ; enable the reception of data from satellites (Space to Ground S2G). By means of a dedicated Optical Ground Station (OGS).

For the next generation of very high throughput communication satellites, free-space optical (FSO) communication between ground stations and geostationary telecommunication satellites is likely to replace conventional RF links. To mitigate atmospheric turbulence, TNO and DLR propose Adaptive Optics (AO) to apply uplink pre-correction. In order to demonstrate the feasibility of AO pre-correction an FSO link has been tested over a 10 km range. This paper shows that AO pre-correction is most advantageous for low point ahead angles (PAAs), as expected. In addition, an optimum AO precorrection performance is found at 16 AO modes for the experimental conditions. For the specific test site, tip-tilt precorrection accounted for 4.5 dB improvement in the link budget. Higher order AO modes accounted for another 1.5 dB improvement in the link budget. From these results it is concluded that AO pre-correction can effectively improve high-throughput optical feeder links.

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We derive approximate equations of motion for excited state dynamics of a multilevel open quantum system weakly interacting with light to describe fluorescence detected single molecule spectra. Based on the Frenkel exciton theory, we construct a model for the chlorophyll part of the LHCII complex of higher plants and its interaction with previously proposed excitation quencher in the form of the lutein molecule Lut 1. The resulting description is valid over a broad range of timescales relevant for single molecule spectroscopy, i.e. from ps to minutes. Validity of these equations is demonstrated by comparing simulations of ensemble and single-molecule spectra of monomeric LHCII with experiments. Using a conformational change of the LHCII protein as a switching mechanism, the intensity and spectral time traces of individual LHCII complexes are simulated, and the experimental statistical distributions are reproduced. Based on our model, it is shown that with reasonable assumptions about its interaction with chlorophylls, Lut 1 can act as an efficient fluorescence quencher in LHCII., Comment: 13 pages, 5 figures and 4 pages of Supplementary Information