Alvaro Morales

Bio: Alvaro Morales is an academic researcher from Eindhoven University of Technology. The author has contributed to research in topics: Photonics & Radio over fiber. The author has an hindex of 5, co-authored 30 publications receiving 85 citations. Previous affiliations of Alvaro Morales include Technical University of Denmark.

Towards a Scaleable 5G Fronthaul: Analog Radio-over-Fiber and Space Division Multiplexing

Abstract: The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6 GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable In this article the use of analog radio-over-fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach–Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800 MHz bandwidth, achieving transmission over 10 km of 7-core single-mode multi-core fiber and 9 m mm-wave wireless at 255 GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction

Highly Tunable Heterodyne Sub-THz Wireless Link Entirely Based on Optoelectronics

Abstract: This article presents the experimental demonstration of a fully photonics-based heterodyne subterahertz (sub-THz) system for wireless communications. A p-i-n photodiode is used as a broadband transmitter to upconvert the signal to the sub-THz domain and a photoconductive antenna downconverts the received wave to an intermediate frequency around 3.7 GHz. The optical signals used for photomixing are extracted from two independent optical frequency combs with different repetition rates. The optical phase locking reduces the phase noise of the sub-THz signal, greatly improving the performance of the system when phase modulation formats are transmitted. The sub-THz carrier is tuned between 80 and 320 GHz in 40-GHz steps, showing a power variation of 21.8 dB. The phase noise at both ends of the communication link is analyzed and compared with the phase noise of the received signal with different wireless carriers. As a proof-of-concept, a 100-Mbit/s binary-phase-shift-keying signal is successfully transmitted over 80-, 120-, and 160-GHz carriers, achieving a bit error rate below 10−5 in the first two cases. These results show the great potential of THz communications driven by photonics to cover an extensive portion of the THz range without relying on electronic components that limit the operating range of the system to a concrete frequency band.

Analog Radio Over Fiber Fronthaul for High Bandwidth 5G Millimeter-Wave Carrier Aggregated OFDM

Abstract: The increasing demands for high capacity and ultra-low latency services require to introduce a 5G mobile communications infrastructure based on a centralized radio access network with space division multiplexed optical fronthaul using radio-over-fiber. The transmission of carrier aggregated 5G OFDM signals over an analog radio-over-fiber fronthaul link is experimentally demonstrated. Multi-Gbit/s data rates are achieved in limited bandwidth, with BER below the 25% overhead FEC limit after millimeter-wave wireless transmission over 2.2 m.

50 GHz optical true time delay beamforming in hybrid optical/mm-wave access networks with multi-core optical fiber distribution

Abstract: We propose and experimentally validate an optical true time delay beamforming scheme with straightforward integration into hybrid optical/millimeter (mm)-wave access networks. In the proposed approach, the most complex functions, including the beamforming network, are implemented in a central office, reducing the complexity and cost of remote antenna units. Different cores in a multi-core fiber are used to distribute the modulated signals to high-speed photodetectors acting as heterodyne mixers. The mm-wave carrier frequency is fixed to 50 GHz (V-Band), thereby imposing a progressive delay between antenna elements of a few picoseconds. That true time delay is achieved with an accuracy lower than 1 ps and low phase noise.

1 Gb/s chaotic encoded W-band wireless transmission for physical layer data confidentiality in radio-over-fiber systems.

Abstract: Physical layer encryption methods are emerging as effective, low-latency approaches to ensure data confidentiality in wireless networks. The use of chaotic signals for data masking is a potential solution to prevent a possible eavesdropper to distinguish between noise and sensitive data. In this work, we experimentally demonstrate the W-band wireless transmission of a 1 Gb/s chaotic signal over 2 m in a radio-over-fiber architecture. The chaos encoding scheme is based on the transition between different states of a Duffing oscillator system, digitally implemented. The bit error rate achieved in all cases was below the forward error correction limit for 7 % overhead. The presented results validate the proposed chaos-based physical layer encoding solution for gigabit data transmissions in hybrid millimeter-wave/photonic networks.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Physical properties of III-V semiconductor compounds : InP, InAs, GaAs, GaP, InGaAs, and InGaAsP

Abstract: Structural Properties Mechanical, Elastic, and Lattice Vibrational Properties Thermal Properties Collective Effects and Some Response Characteristics Electronic Energy-Band Structure Electron and Hole Deformation Potentials Optical Properties Elastooptic and Electrooptic Effects Carrier Transport Properties Strain Problems in InGaAs(P)-Based Heterostructures Concluding Remarks Appendix Indexes.

High-Capacity 5G Fronthaul Networks Based on Optical Space Division Multiplexing

Abstract: The introduction of 5G mobile networks, bringing multi-Gbit/s user data rates and reduced latency, opens new opportunities for media generation, transport and distribution, as well as for new immersive media applications. The expected use of millimeter-wave carriers and the strong network densification resulting from a much reduced cell size—which enable the expected performance of 5G—pose major challenges to the fronthaul network. Space division multiplexing (SDM) in the optical domain has been suggested for ultra-high capacity fronthaul networks that naturally support different classes of fronthaul traffic and further enable the use of analog radio-over-fiber and advanced technologies, such as optical beamforming. This paper discusses the introduction of SDM with multi-core fibers in the fronthaul network as suggested by the blueSPACE project, regarding both digitized and analog radio-over-fiber fronthaul transport as well as the introduction of optical beamforming for high-capacity millimeter-wave radio access. Analog and digitized radio-over-fiber are discussed in a scenario featuring parallel fronthaul for different radio access technologies, showcasing their differences and potential when combined with SDM.

Towards a Scaleable 5G Fronthaul: Analog Radio-over-Fiber and Space Division Multiplexing

Abstract: The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6 GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable In this article the use of analog radio-over-fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach–Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800 MHz bandwidth, achieving transmission over 10 km of 7-core single-mode multi-core fiber and 9 m mm-wave wireless at 255 GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction

Toward 6G Internet of Things and the Convergence With RoF System

Abstract: The Internet of Things (IoT) has been a promising communication paradigm that involves sensors, microcontrollers, and transceivers for an efficient communication and computation system. The infrastructure and the applications shall enable and improve the intelligent management of our city service, workspace, and daily life. This article aims at the future 6G vision of IoT, and discusses the convergence with the Radio-over-Fiber (RoF) system. Comparing with the IoT services included in the 5G deployment, 6G IoT exploits high-density heterogeneous devices involving extremely high capacity, supporting much more robust system architecture and artificial intelligence (AI)-based smart algorithms. The RoF is one of the most promising enablers for the outstanding characters of flexibility and efficiency of 6G IoT systems. This article first introduces the IoT envolution roadmap from 5G toward 6G and the potency of optic fiber and RoF technologies. Then, we present the rapidly expanding RoF market and compatible technologies related to IoT-RoF convergence with the discussion on the current outstanding works in multiple dimensions. Finally, we investigate the challenges ahead for the future RoF supported 6G IoT system and the emerging technology solutions.