Rate-flexible optical CDMA networks based on coherent modulation formats

In this paper, we propose, design, and assess the performance of optical coherent access networks based on optical code-division multiple-access (OCDMA) based on three distinct coherent modulation formats, namely, BPSK, QPSK, and 16-QAM. We design a flexible network architecture based on these coherent modulation formats to provide either single data rate transmissions or multiple data rate transmissions. In this way, the network supports users with the same transmission rate, or group of users transmitting at different data rates. We derive new close-form analytical expressions for both single and multiple rate use cases to assess the performance of the coherent OCDMA network. Results shown that the multi-rate data traffic from the users can coexist almost transparently in terms of network performance. The flexible OCDMA network might be a prospective alternative for implementing coherent systems for different service provision according to traffic demand requirements while supporting with high capacity, security, and simultaneous numbers of subscribers. Keywords: BPSK, QPSK, 16-QAM, coherent network, BER, OCDM

The C-Band accelerating structures for SPARC photoinjector energy upgrade

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Technology developments of ELI-NP gamma beam system

The ELI-NP gamma beam system (GBS) is a linac based gamma-source in construction in Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy, from 0.2 to 19.5 MeV, and with intensity and brilliance beyond the state of the art, will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and an intense laser pulse at 100 Hz repetition rate. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation and laser recirculation at the interaction point. In this paper, the main technological developments carried out by the EuroGammaS consortium for the generation of the ELI-NP gamma beam will be described with a special emphasis on the electron linac technology, such as: RF-gun and C-band accelerating structures design fabrication and tests; low level RF (LLRF) and synchronization systems specifications and development. Finally, the laser recirculation apparatus design is briefly described and first results reported

Erratum to: EuPRAXIA Conceptual Design Report – Eur. Phys. J. Special Topics 229, 3675-4284 (2020), https://doi.org/10.1140/epjst/e2020-000127-8

International audienceThe online version of the original article can be found at http://https://doi.org/10.1140/epjst/e2020-000127-8</A

Bidirectional K-band photonic/wireless link for 5G communications

A bidirectional analogue radio-over-fiber link relying on photonic heterodyning and time-division duplex is experimentally demonstrated, successfully transmitting 5G OFDM signals with data rates of 2.4 Gbit/s and 1.2 Gbit/s in down- and uplink directions over 4 m of wireless distance. An optical frequency comb laser is used together with a demultiplexing module based on injection locking to generate stable K-band (18 – 27 GHz) signals, which eliminates the need for complex high-speed electronics for mm-wave generation

Performance analysis of atmospheric optical communication systems with spatial diversity affected by correlated turbulence

This paper presents a complete analytical framework for obtaining the performance associated with a free-space optical (FSO) communication system with a spatial diversity and equal gain-combining technique. The system is affected by gamma gamma scintillations with different realistic degrees of channel correlation depending only on the physical parameters of the link. We derive new analytical closed-form expressions for the average bit error rate (ABER) considering different scenarios to provide very realistic behavior of the system including different numbers of FSO receivers in several geometric configurations, with different receiving areas, different path lengths, and a variety of turbulence conditions. Furthermore, a very accurate approximate closed-form expression is also derived for the ABER of any generic coding scheme with either a very complex or, directly, no closed-form expression for its associated conditional BER that is first obtained in the ideal case of absence of turbulence. Numerical results via Monte Carlo simulation are provided to corroborate the validity of all the derived analytical expressions