Nikolaos K. Lyras - IEEE Xplore Author Profile

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This paper is focused on the QKD deployment options for mountain communities based on LEO satellite-to-ground downlinks. The satellite QKD usecase for Vovousa village in Zagori is considered in this paper, providing simulation results for infrastructure deployment options that can support the implementation of LEO satellite DS-BB84 QKD protocol. SKR analysis is provided using an already available ...Show More
This paper presents a comprehensive feasibility analysis designed to model Low Earth Orbit (LEO) satellite-to-ground communications for Quantum Key Distribution (QKD), focusing on the 1550nm wavelength to facilitate the distribution of information through fiber segments. Discrete Variable Decoy State Polarization-based BB84 protocol is assumed whereas various detection setups and environmental con...Show More
We propose a WDM-enabled optical architecture in support of optimized classical/QKD coexistence over the deployed fiber/FSO infrastructure for 6G communications. A detailed analysis of 4-channel C-band WDM Classical/Quantum coexistence over deployed fiber/FSO links was conducted, showcasing the feasibility of QKD links for intra-campus connections in both mediums revealing QBER values (<3.2%) unde...Show More
Optical satellite links and networks are currently being deployed by various space agencies and the industry for space, deep-space applications and intersatellite links. In this paper, a REINFORCE-based solution is presented for optimal power allocation regarding an optical geostationary satellite-to- ground system. Specifically, the proposed algorithm is channel model-free, and learns through a c...Show More
This article presents an in-depth satellite-to-ground quantum key distribution (QKD) feasibility analysis between a low Earth orbit (LEO) satellite and a 0.28-m small-sized optical ground stations (OGSs) located in urban areas, over night time. Both prepare-and-measure (P&M) and entanglement (ENT)-based QKD protocols are employed and compared in terms of distilled key bits. The performance of vari...Show More
This paper is focused on the experimental demonstration of Analog Over Fiber systems over converged Fiber/Free Space Optical links enabling the X-haul connectivity in beyond 5G and 6G era. More specifically, we present an experimental campaign of Radio over Fiber transmission of diverse waveforms over hybrid Fiber/ Free Space Optical links scenarios. Initially, we present a brief link budget analy...Show More
Optoelectronic technology is expected to be the cornerstone of sub-THz communication systems, enabling access to and use of the vast frequency resources found in this portion of the spectrum. In this work we demonstrate a photonics-enabled sub-THz wireless link operating in real-time settings, using a PIN-PD-based THz emitter, and a THz receiver based on an ultra-fast photoconductor. The real-time...Show More
We demonstrate the generation, of a mmWave signal via the injection of an optical frequency comb (OFC) into an integrated tunable dual distributed Bragg reflector (DBR) laser as well as the fiber transmission and the processing of this signal by an optical beamforming network (OBFN). The dual DBR laser is based on a hybrid indium phosphide (InP) – polymer photonic integrated circuit (PIC). Two dif...Show More
As Quantum Key Distribution (QKD) seems to turn towards satellite communication infrastructure to interconnect distant nodes aiming to a global quantum secured network, the number of assisting satellites is expected to increase. In this work, a feasibility analysis of a large-scale Low Earth Orbit (LEO) satellite constellation supporting LEO to ground QKD links is presented. A software tool to sim...Show More
A research contribution focusing on the feasibility of the Decoy State BB84 Quantum Key Distribution (QKD) protocol over a free-space optical (FSO) link under strong and moderate solar radiance in the urban environment of Athens city, Greece for short distances up to 1km is presented. Emphasis is placed on the time varying attenuation which is introduced by various atmospheric processes and especi...Show More
We demonstrate a broadband and continuously tunable 1×4 optical beamforming network (OBFN), based on the hybrid integration of indium phosphide (InP) components in the silicon nitride (Si3N4) platform. The photonic integrated circuit (PIC) comprises a hybrid InP-Si3N4 external cavity laser, a pair of InP phase modulators, a Si3N4 optical single-sideband full carrier (SSBFC) filter followed by four...Show More
In this paper, we validate the intrinsic capability of optical beamforming networks (OBFNs) to support simultaneously multi-beam and multicast operations. Through simulation analyses and assuming operation in the downlink direction of a wireless system, we verify the capability of an OBFN based on Blass-matrix architecture and an OBFN based on true-time delay (TTD) elements to support this hybrid ...Show More
Optical satellite networks have been recently proposed as an alternative solution of backhaul satellite networks. In this paper, simple algorithms for the optimum selection of the locations of optical ground stations (OGSs) in a Medium Earth Orbit (MEO) optical satellite system are presented. The objective is to satisfy an availability threshold for each month and for each orbital position of the ...Show More
This contribution is focused on MEO satellite communication systems operating at optical wavelengths, and especially on the optimum dimensioning of their optical ground station (OGS) network (OGSN). The objective of the optimization is to minimize the size of the network, while still ensuring the target link availabilities due to cloud blockage. Two new optimization algorithms for this optimum sel...Show More
As in other facets of society, the data rate requirements of science and exploration missions in deep space are ever-increasing, mostly due to the number and refinement of science instruments onboard the spacecraft. For repatriating the increased data back to Earth, the communication link is the bottleneck. To tackle this issue for future missions, space agencies in the frame of Consultative Commi...Show More
Optical satellite communication systems are severely affected by the cloud coverage. Therefore, for the evaluation of system's availability Cloud Free Line of Sight statistics of the optical ground stations (OGSs) must be estimated. The elevation angles and the altitude of the OGSs should be considered for the accurate prediction and reliable evaluation of the optical satellite network performance...Show More
In this paper, the ground-to-satellite optical links and especially optical feeder links are studied. A methodology for the derivation of received power statistics taking into considerations the phenomena that degrade the optical signal and especially the turbulence effects is reported. The methodology is validated in terms of the first order statistics with experimental data from the ARTEMIS bidi...Show More
Satellite communication networks at optical frequencies have been proposed to provide a very high throughput for backhauling applications. In this letter, the monthly variation of cloud coverage statistics is investigated and exploited for the optimum selection of optical ground stations. Optimization algorithms for the selection of the minimum number of ground stations satisfying the monthly avai...Show More
The employment of optical frequencies in satellite communication systems has been proposed in order to cover the huge needs for capacity in the next decade. The reliable design and the prediction of the performance of optical satellite links need accurate channel modeling in the form of time series generators. Considering cloud free line-of-sight (CFLOS) satellite links, turbulence effects on the ...Show More
In this paper, the performance of a reference medium earth orbit (MEO) satellite constellation system operating at Ka-band and employing single links to ground is compared with next generation advanced systems in higher RF or optical bands employing multiple diversity links. The fill rate of existing MEO constellations offering broadband and trunking services in Ka-band is growing fast, rendering ...Show More
Analytical models for the prediction of cloud-free line-of-sight (CFLOS) probability for a single optical satellite link and for multiple spatially separated optical satellite links are presented. The presence of clouds along the slant paths causes their blockage. As a result, an ON/OFF channel with the presence of clouds is assumed. The proposed model for the calculation of CFLOS considers the el...Show More
The impact of cloud impairments on satellite links is increasing with the employment of higher frequency bands. In this paper, a model for predicting cloud attenuation statistics for satellite communication systems operating from Ka-band to optical range is presented. The cloud attenuation must be accurately quantified for the reliable design of satellite communication systems. A stochastic dynami...Show More
The reliable design of modern satellite communication systems operating above 10GHz requires the accurate evaluation of the channel modeling. Rain attenuation is the dominant fading mechanism for satellite links at Ku, Ka and Q/V band. Channel modeling is also important for the optimum design of the Fade Mitigation Techniques (FMTs). In this paper we present annual, seasonal, and diurnal simulated...Show More
This paper provides a new stochastic model for the calculation of cloud attenuation time series for Earth-space links at optical frequencies. The presented methodology is based on the employment of stochastic differential equations for the generation of time series of cloud fields. More specifically, we propose a dynamic stochastic model for the evaluation of Integrated Liquid Water Content (ILWC)...Show More