Abstract-A novel remote antenna unit, intended for application in the downlink of an analog radio frequency over fiber system, is proposed, whose radiated power originates entirely from the optical signal supplied by a single multi-mode fiber. By operating the photodetector of the optical receiver at zero bias voltage, while omitting typical active components, such as transimpedance amplifiers, a fully passive unit, requiring no external power supply, is obtained. Instead, a careful co-design is performed to maximize the power transfer from photodetector to antenna within the frequency range of interest using an impedance matching network. A wideband cavity-backed slot antenna is implemented in air-filled substrate-integrated-waveguide technology. The antenna feed plane serves as integration platform for the optical receiver. The resulting downlink remote antenna unit is compact, cost-effective, energy-efficient and extremely reliable. Therefore, it is an ideal building block for novel, highly specialized, ultra-high density wireless communication systems, which require massive amounts of remote antenna units, deployed in attocells as small as 15 cm ×15 cm. A prototype operating in a wide frequency bandwidth ranging from 3.30 GHz to 3.70 GHz is constructed and validated. In free-space conditions, a broadside gain of −0.2 dBi, a front-to-back ratio of 8.8 dB and linear polarization with a cross-polarization level of −28.8 dB are measured at 3.50 GHz. Furthermore, a −3 dB gain bandwidth of 500 MHz is observed. Finally, the prototype is deployed in a unidirectional data link, achieving a symbol rate of 80 MBd over a distance of 20 cm.

Transceivers based on electro-absorption modulators are considered as a promising candidate for the next generation 400 GbE short-reach optical networks. They are capable of combining high bandwidth and low-power operation with a very compact layout, removing the need for traveling wave electrodes and dedicated 50 Ω termination. In this paper we demonstrate the first silicon-based EAM, in combination with an in-house developed SiGe BiCMOS transceiver chipset, capable of transmitting single-lane 100 Gb/s non-return-to-zero in realtime. Transmission up to 500 m of standard single mode fiber and 2 km of non-zero dispersion shifted fiber is demonstrated, assuming a forward-error coding scheme with a bit-error rate limit of 3.8×10 −3 is used. Due to the high line rate, transmission over longer fiber spans was limited by the chromatic distortion in the fiber. As a possible solution, electrical duobinary modulation is proposed as it is more resilient to this type of fiber distortion by reducing the required optical bandwidth. We show improved performance for longer fiber spans with a 100 Gb/s electrical duobinary link, resulting in real-time sub-FEC operation over more than 2 km of standard single-mode fiber without any digital signal processing. Finally, the possibility of a 100 Gb/s EAM-to-EAM link is investigated.

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Beyond-5G wireless systems require significant improvement to enable the Internet of Everything, offering ultrareliability, ultra-low-latency and high data-rates for holographic telepresence, immersive augmented and virtual reality, and cyber-physical systems in Industry 4.0. The mmWave frequency band (30 GHz-300 GHz) provides the required bandwidths, but very challenging propagation conditions exist. Conventional co-located multi-antenna systems counter higher path loss, but are insufficient in challenging real-life scenarios with frequent non-line-of-sight conditions. For distributed massive MIMO systems or large intelligent surfaces, we advocate optically-enabled distributed antenna systems (DAS) to alleviate these issues. To ensure tight synchronization and scalability, we propose a mmWave-over-fiber based architecture with low-complexity high-performance remote antenna units (RAUs). Strategically distributing and integrating RAUs in the user equipments' environment yield high throughput and reliable coverage. We demonstrate a mmWave-over-fiber DAS yielding multi-Gbps mmWave communication in a harsh indoor environment with non-line-of-sight conditions, measuring wireless data rates up to 24 Gbps, by selecting the RAU yielding the best link quality, and up to 48 Gbps, by leveraging distributed MIMO techniques.