In this study a feasibility analysis of a satellite-to-ground QKD link employing the Decoy-State BB84 protocol for both LEO and MEO satellite constellations is presented. Considering realistic atmospheric conditions and system assumptions, a comparison of the QKD performance between low and medium satellite orbits over an existing OGS network is reported.
A novel transmitter implementation, which will be capable of operating in both classical and quantum light regimes since it will be able to send single photons across a quantum channel and at the same time to serve as analog RoF transmitter currently deployed in X-haul topologies, is proposed. By spectrally isolating the sidebands of analog RoF signal and by controlling the EML’s modulation index, different mean photon numbers launched in one sideband can be obtained. We report on the architecture of our proposed transmitter station, and we demonstrate its operation through proof-of-concept experiments by performing successful RoF transmission links and by carrying out photon-counting measurements. The transmission of 200 Mbaud QPSK-modulated signal with acceptable EVM measurements of < 17.5%, as well the variation of the mean count rate of the filtered sideband as a function of the peak-to-peak driving voltage of radio signal at 28GHz were successfully performed, confirming that the sidebands of A-RoF transceivers can be used as single-photon carriers for quantum information.
Photonic integrated circuits (PICs) are one of the key enablers for beyond 5G networks. A novel generation of fully integrated photonic-enabled transceivers operating seamlessly in W- D- and THz-bands is developed within the EU funded project TERAWAY. Photonic integration technology enables key photonic functionalities on a single PIC including photonic up/down conversion. For efficient down-conversion at the photonic integrated receiver, we develop the first waveguide-fed photoconductive antenna for THz communications. Finally, we report on the experimental implementation of a fully photonic-enabled link operating across W- D- and THz-bands.
For enabling and realizing long-haul Quantum Key Distribution (QKD), satellite communication infrastructure is exploited to deliver symmetric encryption keys to ground segments. In this direction the European Quantum Communication Infrastructure (Euro-QCI) initiative, supported by the European Space Agency (ESA), aims to build a secure quantum communication network that will span across the EU. In this framework, ESA has selected three observatories in Greece to support European activities in optical communications and QKD systems. In this study, a QKD feasibility analysis between a LEO satellite constellation (100 satellites) and the three selected Optical Ground Stations (OGSs) in Greece, using an entangled based QKD protocol is presented. This contribution focuses on the performance evaluation and the applicability validation of an entanglement-based QKD system in a pragmatic regional segment of Euro-QCI. The time varying atmospheric channel is modeled taking into account the joint cloud coverage of the OGSs, the turbulence, the pointing errors and the solar background radiance. The performance of the regional entangled-based QKD system is validated in terms of annual availability as well as the number of shared distilled key bits between the ground stations per year.
Free space optics (FSO) is considered a promising technology for satellite communications due to its various advantages over radio-frequency (RF) systems, such as higher throughput, lower energy consumption and smaller mass. Nevertheless, optical satellite communication systems are heavily affected by atmospheric impairments, mainly by clouds. In order to cope with cloud coverage, site diversity technique is employed at the expense of installing extra optical ground stations (OGSs). As a consequence, the interest in ground network optimization is rapidly increasing with the aim to guarantee a given service availability. In this paper, a low-complexity optimization algorithm for ground network design in optical geostationary (GEO) satellite systems is presented, taking into account the spatial correlation between sites. Specifically, the objective is to choose a group of candidate OGSs that minimizes the overall cost of the ground network and meets certain availability requirements for every time period (thus incorporating the temporal variability of cloud coverage). Moreover, an extension of the methodology to optical medium-Earth-orbit (MEO) satellite systems is provided. Lastly, the performance of the proposed algorithm is evaluated via numerical experiments.
In this paper, a methodology for the generation of cloud free line of site time series for low earth orbit optical satellite communication systems is presented. The proposed methodology is based on the synthesis of 3D cloud fields employing Integrated Liquid Water Content (ILWC) statistics. The methodology captures the temporal and spatial variability of cloud coverage and takes into account the varying elevation angle of the LEO optical link with each optical ground station (OGS) and the altitude of each OGS for the estimation of the CFLOS probability. The ILWC statistical parameters required for the CFLOS time series are taken from ERA Interim data base, European Centre for Medium- Range Weather Forecasts (ECMWF). Finally CFLOS numerical results are reported and some significant conclusions are drawn.
In this paper, a methodology for the estimation of aperture averaging factor for a central obscured aperture is briefly presented and tested against experimental results. The modeling is based on the methodology reported in the NASA’s report edited by Fried [10]. For the validation of the methodology, experimental data from the ARTEMIS bi-directional optical link is employed. Experimental data sessions from 2003 with the ARTEMIS GEO satellite as space segment and the 1.016m Cassegrain central obscured telescope of ESA in Tenerife at 2.4km altitude as ground segment are used.
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