Perovskite is an emerging low-cost and high-quality material, that show significant potential to revolutionize photovoltaic and lighting sectors in Organic and Large Area Electronics (OLAE) devices. Their simple and inexpensive processing methods, such as solution-based synthesis and printing, make them attractive for flexible and lightweight electronic devices. In this work, perovskite suitability has been tested for telecommunication applications, particularly Li-Fi links. The perovskite devices were integrated into a telecom system, including an FPGA handling signal processing, LED array, analog transmitter circuitry, and driving electronics for the perovskite photodiode. 4-PPM modulation format has been adopted due to resilience in low SNR. The purpose is to thoroughly characterize the setup to assess the suitability of perovskite devices for Li-Fi scenarios or combined PV and Li-Fi usage. This research aims to advance the application of perovskites in telecommunication and expand their potential in various electronic devices.
Physical Layer Security (PLS) exploits characteristics and properties of the physical layer for data encryption and supplements conventional cryptography for enhanced overall security. Most of the PLS methodologies rely on the (statistical) characteristics of the transmission channel to either generate secure encryption keys, or to exploit them together with other physical layer characteristics (i.e. advanced modulation schemes) for secure transmission. However, these approaches often lead to increased complexity and therefore become impractical for actual system implementation. Recent advancements in Quantum Key Distribution (QKD) systems allow for the utilization of ultra-secure and robust high-rate key exchange. In this work, we propose and describe practical techniques for exploiting and seamlessly integrating highrate QKD keys to encrypt modulation parameters and quantities of conventional modulation schemes like M-QAM, DMT and OFDM of communication links. Moreover, we present transmission scenarios, integrating QKD-PLS in free space optics links, together with their numerical evaluation. The main advantage of QKD exploitation to the proposed solutions comes from the seamless and transparent integration and application of high-rate keys which can either be used in their original form or feed a pseudo-random number generator, to modify the modulation properties/symbols in very high rates, such that eavesdropping and decoding of the encrypted information becomes almost impossible. Additionally, we present the architecture of a real time practical system utilizing and seamlessly integrating the QKD keys into transceiver links to form a robust and ultra-secure PLS ecosystem.
KEYWORDS: Light emitting diodes, Receivers, Modulation, Non-line-of-sight propagation, Signal to noise ratio, Transmitters, System on a chip, Forward error correction, Atmospheric optics
Non-Line-of-Sight (NLOS) optical communication systems have attracted a lot of interest the last few years due to their obvious advantages, such as no requirements for optical beam tracking, non-destructive impact of obstacles on performance etc. Utilization of optical carriers in the UV-C band offers additional advantages profiting from the strong optical scattering, very low optical background noise due to ozone absorption in the atmosphere and inherent security since the UV-C radiation is strongly attenuated with distance. So far, the main focus of the demonstrated experiments has been on point-to-point communication systems. In this paper, we report on the implementation and initial performance characteristics of a peer-to-peer network consisting of nodes interconnected through scattered UV-C light. At the transmissions part, each node consists of four properly spatially arranged groups, with four UV-C LEDs per group, emitting at 265 nm. Each LED group is adjusted at a certain elevation angle. Moreover, each node has three receivers based on Photomultiplier Tubes (PMΤs) including a UV-C bandpass optical filter in front of each PMT to further reduce the background noise due to the non-zero responsivity of each PMT in the UV-B band. The modulation scheme adopted in the experiments is the 4-PPM (Pulse Position Modulation). The bit rate at the physical layer is close to 7.80 kbit/s. In the link layer, the rules for communication and collisions avoidance between nodes are also set. The first results for 15 meters distance with focus on the physical layer show that the concept is realistic.
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