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In this paper, we demonstrate a real-time high-resolution analogue-to-digital-based free-space optics system. We utilise a field-programmable gate array platform complete with system-on-chip to flexibly implement the orthogonal frequency division multiplexing (OFDM) with up to 2048 sub-carriers and carrier-less amplitude and phase (m-CAP) modulation with up to 20 sub-bands in a real free-space optical link for the first time. We also consider high order modulation formats up to 64-QAM (6 bits/symbol) to achieve a raw data rate up to 1.8 Gb/s. Previous real-time free-space optics transceivers were either analog-based or restricted to on-off keying (1 bit/symbol). We emulate the fog environment utilising neutral density filters and evaluate the performance of the link under increasingly poor visibility conditions. We show that OFDM and m-CAP offer similar performances in the link environment, however, we finally show that m-CAP offers increased robustness and receiver sensitivity in low visibility settings. [ABSTRACT FROM AUTHOR]

Free-Space Optical (FSO) systems offer the ability to distribute high speed digital links into remote and rural communities where terrain, installation cost or infrastructure security pose critical hurdles to deployment. A challenge in any point-to-point FSO system is initiating and maintaining optical alignment from the sender to the receiver. In this paper we propose and demonstrate a low-complexity self-aligning FSO prototype that can completely self-align with no requirement for initial manual positioning and could therefore form the opto-mechanical basis for a mesh network of optical transceivers. The prototype utilises off-the-shelf consumer electrical components and a bespoke alignment algorithm. We demonstrate an eight fibre spatially multiplexed link with a loss of 15 dB over 210 m. [ABSTRACT FROM AUTHOR]

Innovations in ‘sustainable’ photonics technologies such as free-space optical links and solar-powered equipment provide developing countries with new cost-effective opportunities for deploying future-proof telecommunication networks. [ABSTRACT FROM AUTHOR]