Conversion analogique-numérique Sigma-Delta large bande appliquée à la mesure des non-linéarités des amplificateurs de puissance

Power amplifiers, which are essential elements of any communication system, will play a crucial role in the development of future communication systems. Today improving power amplifiers requires technological advances at the circuit device level, but one also must consider a more global approach. In particular, advances in digital processing can now correct in the early stage of the communication chain some distortions that are generated downstream in the chain. Digital pre-distortion is a correction technique for power amplifiers that has a growing interest because of its completely digital implementation and of its gains in linearity and energy consumption. This technique requires a feedback path where the analog-to-digital converter is a critical element. This component must satisfy the constraints of high resolution , wide bandwidth, and high linearity. In this thesis, we propose a new architecture of analog-to-digital converter based on bandpass Delta-Sigma modulators. This architecture takes advantage of operating bandpass modulators that are designed to work in parallel, each focusing on different frequencies, but also of a particular cascading arrangement to eliminate the useful signal, which has a high power, in order to reduce dynamics constraints. High-level design and simulations were carried out for discrete time and continuous time systems and also required the development of appropriate simulation tools.Les amplificateurs de puissance, éléments constitutifs essentiels de tout système de télécommunication, vont jouer un rôle capital dans le développement des futurs systèmes de communication. Aujourd'hui l'amélioration des amplificateurs de puissance nécessite un progrès technologique au niveau du composant lui même mais doit aussi tenir compte d'une approche plus globale. En particulier, le progrès dans les traitements numériques permet aujourd'hui de corriger en amont certaines distorsions qui seront générées en aval de la chaîne de communication. La pré-distorsion numérique est une technique de correction des amplificateurs de puissance qui connaît un intérêt grandissant de par son intégration complètement numérique et par les gains en linéarité et en consommation. Cette technique nécessite une voie de retour dont un élément critique est le convertisseur analogique-numérique. Ce composant doit répondre à des contraintes de résolution, de bande passante et de linéarité élevées. Dans cette thèse, nous proposons une nouvelle architecture de convertisseur analogique-numérique à base de modulateurs Sigma-Delta passe-bande. Cette architecture tire partie du fonctionnement passe bande des modulateurs que nous faisons travailler en parallèle, chacun centré sur différentes fréquences, mais aussi d'un agencement en cascade particulier pour éliminer le signal utile, qui est de forte puissance, dans le but de diminuer les contraintes de dynamique.La conception haut niveau et les simulations ont été menées pour des systèmes à temps discret et aussi à temps continu et a nécessité le développement d'outils adaptés de simulation se basant sur la boîte à outils Delta Sigma Toolbox de Richard Schreie

Receiver design for nonlinearly distorted OFDM : signals applications in radio-over-fiber systems

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 201

Novel linear and nonlinear optical signal processing for ultra-high bandwidth communications

The thesis is articulated around the theme of ultra-wide bandwidth single channel signals. It focuses on the two main topics of transmission and processing of information by techniques compatible with high baudrates. The processing schemes introduced combine new linear and nonlinear optical platforms such as Fourier-domain programmable optical processors and chalcogenide chip waveguides, as well as the concept of neural network. Transmission of data is considered in the context of medium distance links of Optical Time Division Multiplexed (OTDM) data subject to environmental fluctuations. We experimentally demonstrate simultaneous compensation of differential group delay and multiple orders of dispersion at symbol rates of 640 Gbaud and 1.28 Tbaud. Signal processing at high bandwidth is envisaged both in the case of elementary post-transmission analog error mitigation and in the broader field of optical computing for high level operations (“optical processor”). A key innovation is the introduction of a novel four-wave mixing scheme implementing a dot-product operation between wavelength multiplexed channels. In particular, it is demonstrated for low-latency hash-key based all-optical error detection in links encoded with advanced modulation formats. Finally, the work presents groundbreaking concepts for compact implementation of an optical neural network as a programmable multi-purpose processor. The experimental architecture can implement neural networks with several nodes on a single optical nonlinear transfer function implementing functions such as analog-to-digital conversion. The particularity of the thesis is the new approaches to optical signal processing that potentially enable high level operations using simple optical hardware and limited cascading of components

Roadmap of optical communications

© 2016 IOP Publishing Ltd. Lightwave communications is a necessity for the information age. Optical links provide enormous bandwidth, and the optical fiber is the only medium that can meet the modern society's needs for transporting massive amounts of data over long distances. Applications range from global high-capacity networks, which constitute the backbone of the internet, to the massively parallel interconnects that provide data connectivity inside datacenters and supercomputers. Optical communications is a diverse and rapidly changing field, where experts in photonics, communications, electronics, and signal processing work side by side to meet the ever-increasing demands for higher capacity, lower cost, and lower energy consumption, while adapting the system design to novel services and technologies. Due to the interdisciplinary nature of this rich research field, Journal of Optics has invited 16 researchers, each a world-leading expert in their respective subfields, to contribute a section to this invited review article, summarizing their views on state-of-the-art and future developments in optical communications

Radio over fiber enabling PON fronthaul in a two-tiered cloud

Avec l’avènement des objets connectés, la bande passante nécessaire dépasse la capacité des interconnections électriques et interface sans fils dans les réseaux d’accès mais aussi dans les réseaux coeurs. Des systèmes photoniques haute capacité situés dans les réseaux d’accès utilisant la technologie radio sur fibre systèmes ont été proposés comme solution dans les réseaux sans fil de 5e générations. Afin de maximiser l’utilisation des ressources des serveurs et des ressources réseau, le cloud computing et des services de stockage sont en cours de déploiement. De cette manière, les ressources centralisées pourraient être diffusées de façon dynamique comme l’utilisateur final le souhaite. Chaque échange nécessitant une synchronisation entre le serveur et son infrastructure, une couche physique optique permet au cloud de supporter la virtualisation des réseaux et de les définir de façon logicielle. Les amplificateurs à semi-conducteurs réflectifs (RSOA) sont une technologie clé au niveau des ONU(unité de communications optiques) dans les réseaux d’accès passif (PON) à fibres. Nous examinons ici la possibilité d’utiliser un RSOA et la technologie radio sur fibre pour transporter des signaux sans fil ainsi qu’un signal numérique sur un PON. La radio sur fibres peut être facilement réalisée grâce à l’insensibilité a la longueur d’onde du RSOA. Le choix de la longueur d’onde pour la couche physique est cependant choisi dans les couches 2/3 du modèle OSI. Les interactions entre la couche physique et la commutation de réseaux peuvent être faites par l’ajout d’un contrôleur SDN pour inclure des gestionnaires de couches optiques. La virtualisation réseau pourrait ainsi bénéficier d’une couche optique flexible grâce des ressources réseau dynamique et adaptée. Dans ce mémoire, nous étudions un système disposant d’une couche physique optique basé sur un RSOA. Celle-ci nous permet de façon simultanée un envoi de signaux sans fil et le transport de signaux numérique au format modulation tout ou rien (OOK) dans un système WDM(multiplexage en longueur d’onde)-PON. Le RSOA a été caractérisé pour montrer sa capacité à gérer une plage dynamique élevée du signal sans fil analogique. Ensuite, les signaux RF et IF du système de fibres sont comparés avec ses avantages et ses inconvénients. Finalement, nous réalisons de façon expérimentale une liaison point à point WDM utilisant la transmission en duplex intégral d’un signal wifi analogique ainsi qu’un signal descendant au format OOK. En introduisant deux mélangeurs RF dans la liaison montante, nous avons résolu le problème d’incompatibilité avec le système sans fil basé sur le TDD (multiplexage en temps duplexé).With the advent of IoT (internet of things) bandwidth requirements triggered by aggregated wireless connections have exceeded the fundamental limitation of copper and microwave based wireless backhaul and fronthaul networks. High capacity photonic fronthaul systems employing radio over fiber technology has been proposed as the ultimate solution for 5G wireless system. To maximize utilization of server and network resources, cloud computing and storage based services are being deployed. In this manner, centralized resources could be dynamically streamed to the end user as requested. Since on demand resource provision requires the orchestration between the server and network infrastructure, a smart photonic (physical layer)PHY enabled cloud is foreseen to support network virtualization and software defined network. RSOAs (Reflective Semiconductor Optical Amplifier) are being investigated as key enablers of the colorless ONU(Optical Network Unit) solution in PON (Passive Optical Network). We examine the use of an RSOA in radio over fiber systems to transport wireless signals over a PON simultaneously with digital data. Radio over fiber systems with flexible wavelength allocation could be achieved thanks to the colorless operation of the RSOA and wavelength reuse technique. The wavelength flexibility in optical PHY are inline with the paradigm of software defined network (SDN) in OSI layer 2/3. The orchestration between optical PHY and network switching fabric could be realized by extending the SDN controller to include optical layer handlers. Network virtualization could also benefit from the flexible optical PHY through dynamic and tailored optical network resource provision. In this thesis, we investigate an optical PHY system based on RSOA enabling both analog wireless signal and digital On-Off Keying (OOK) transportation within WDM (Wavelength Division Multiplexing) PON architecture. The RSOA has been characterized to show its potential ability to handle high dynamic range analog wireless signal. Then the RF and IF radio over fiber scheme is compared with its pros and cons. Finally we perform the experiment to shown a point to point WDM link with full duplex transmission of analog WiFi signal with downlink OOK signal. By introducing two RF mixer in the uplink, we have solved the incompatible problem with TDD (Time Division Duplex) based wireless system

Cost-Effective Spectrally-Efficient Optical Transceiver Architectures for Metropolitan and Regional Links

The work presented herein explores cost-effective optical transceiver architectures for access, metropolitan and regional links. The primary requirement in such links is cost-effectiveness and secondly, spectral efficiency. The bandwidth/data demand is driven by data-intensive Internet applications, such as cloud-based services and video-on-demand, and is rapidly increasing in access and metro links. Therefore, cost-effective optical transceiver architectures offering high information spectral densities (ISDs > 1(b/s)/Hz) need to be implemented over metropolitan distances. Then, a key question for each link length and application is whether coherent- or direct (non-coherent) detection technology offers the best cost and performance trade-off. The performance and complexity limits of both technologies have been studied. Single polarization direct detection transceivers have been reviewed, focusing on their achievable ISDs and reach. It is concluded that subcarrier modulation (SCM) technique combined with single sideband (SSB) and high-order quadrature amplitude modulation (QAM) signaling, enabled by digital signal processing (DSP) based optical transceivers, must be implemented in order to exceed an ISD of 1 (b/s)/Hz in direct-detection links. The complexity can be shifted from the optical to the electrical domain using such transceivers, and hence, the cost can be minimized. In this regard, a detailed performance comparison of two spectrally-efficient direct detection SCM techniques, namely Nyquist-SCM and OFDM, is presented by means of simulations. It is found out that Nyquist-SCM format offers the transmission distances more than double that of OFDM due to its higher resilience to signal-signal beating interference. Following this, dispersion-precompensated SSB 4- and 16-QAM Nyquist-SCM signal formats were experimentally demonstrated using in-phase and quadrature (IQ)-modulators at net optical ISDs of 1.2 and 2 (b/s)/Hz over 800 km and 323 km of standard single-mode fibre (SSMF), respectively. These demonstrations represent record net optical ISDs over such distances among the reported single polarization wavelength division multiplexed (WDM) systems. Furthermore, since the cost-effectiveness is crucial, the optical complexity of Nyquist-SCM transmitters can be significantly reduced by using low-cost modulators and high-linewidth lasers. A comprehensive theoretical study on SSB signal generation using IQ- and dual-drive Mach-Zehnder modulators (DD-MZMs) was carried out to assess their performance for WDM direct detection links. This was followed by an experimental demonstration of WDM transmission over 242 km of SSMF with a net optical ISD of 1.5 (b/s)/Hz, the highest achieved ISD using a DD-MZM-based transmitter. Following the assessment of direct detection technology using various transmitter designs, cost-effective simplified coherent receiver architectures for access and metro networks have been investigated. The optical complexity of the conventional (polarization- and phase-diverse) coherent receiver is significantly simplified, i.e., consisting of a single 3 dB coupler and balanced photodetector, utilizing heterodyne reception and Alamouti polarization-time block coding. Although the achievable net optical ISD is halved compared to a conventional coherent receiver due to Alamouti coding, its receiver sensitivity provides significant gain over a direct detection receiver at M-ary QAM formats where M ≥16

Optimised Radio over Fibre Links for Next Generation Radio Access Networks

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonOptical fibre has become the dominant theme of transmission in long haul, high data rate communication systems due to its tremendous bandwidth and low loss. Radio over Fibre (RoF) technology facilitates the seamless integration between wireless and optical communication systems and found to be the most promising solution to meet the exponential bandwidth demands expected for the upcoming years. However, the main bit-rate/distance limitation in RoF systems is the chromatic dispersion. In this thesis, the two generations of RoF technologies, namely Analogue RoF (ARoF) and Digital RoF (DRoF) are investigated. The overall aim of this research is to optimise the optical bandwidth utilisation of these two approaches for a typical transmission of the fronthaul link proposed in the next generation Centralised Radio Access Network (C-RAN). Consequently, a number of physical layer design scenarios for the optimised transmission of the Radio Frequency (RF) signals over a Standards Single Mode Fibre (SSMF) are demonstrated. Firstly, for an ARoF transmission, where the analogue RF signals are transported over SSMF using an optical carrier, a bidirectional link transmitting four Downlink/Uplink channels in a chromatic dispersion limited scenario is designed. Simulation results have shown a clear constellation diagram of a 2.5 Gb/s RF signal transmission over 120 km fibre length. Secondly, a DRoF system with reduced optical bandwidth occupancy is proposed. This system employs an optical Duobinary transmission to the digitised RF signal at the transmitter side to reduce its spectrum and to address the chromatic dispersion effect, simultaneously. Simulation results demonstrate the capability of the proposed system to maintain high-quality transmission of the digitised signals over 70 km of fibre distance without dispersion compensation requirements. Finally, an advanced DRoF transmission link based on integrating digital Optical Single Sideband (OSSB) transmission with Duobinary encoding scheme is designed. Simulation results have clearly verified system’s robustness against transmission impairments and have better performances in terms of the obtained BER and EVM with respect to the 3GPP standardised values. Moreover, the results show that both transmission distance and power budget are furtherly improved in comparison with two other digital transmission scenarios

High Performance Optical Transmitter Ffr Next Generation Supercomputing and Data Communication

High speed optical interconnects consuming low power at affordable prices are always a major area of research focus. For the backbone network infrastructure, the need for more bandwidth driven by streaming video and other data intensive applications such as cloud computing has been steadily pushing the link speed to the 40Gb/s and 100Gb/s domain. However, high power consumption, low link density and high cost seriously prevent traditional optical transceiver from being the next generation of optical link technology. For short reach communications, such as interconnects in supercomputers, the issues related to the existing electrical links become a major bottleneck for the next generation of High Performance Computing (HPC). Both applications are seeking for an innovative solution of optical links to tackle those current issues. In order to target the next generation of supercomputers and data communication, we propose to develop a high performance optical transmitter by utilizing CISCO Systems®\u27s proprietary CMOS photonic technology. The research seeks to achieve the following outcomes: 1. Reduction of power consumption due to optical interconnects to less than 5pJ/bit without the need for Ring Resonators or DWDM and less than 300fJ/bit for short distance data bus applications. 2. Enable the increase in performance (computing speed) from Peta-Flop to Exa-Flops without the proportional increase in cost or power consumption that would be prohibitive to next generation system architectures by means of increasing the maximum data transmission rate over a single fiber. 3. Explore advanced modulation schemes such as PAM-16 (Pulse-Amplitude-Modulation with 16 levels) to increase the spectrum efficiency while keeping the same or less power figure. This research will focus on the improvement of both the electrical IC and optical IC for the optical transmitter. An accurate circuit model of the optical device is created to speed up the performance optimization and enable co-simulation of electrical driver. Circuit architectures are chosen to minimize the power consumption without sacrificing the speed and noise immunity. As a result, a silicon photonic based optical transmitter employing 1V supply, featuring 20Gb/s data rate is fabricated. The system consists of an electrical driver in 40nm CMOS and an optical MZI modulator with an RF length of less than 0.5mm in 0.13&mu m SOI CMOS. Two modulation schemes are successfully demonstrated: On-Off Keying (OOK) and Pulse-Amplitude-Modulation-N (PAM-N N=4, 16). Both versions demonstrate signal integrity, interface density, and scalability that fit into the next generation data communication and exa-scale computing. Modulation power at 20Gb/s data rate for OOK and PAM-16 of 4pJ/bit and 0.25pJ/bit are achieved for the first time of an MZI type optical modulator, respectively

Design and analysis of multi-element antenna systems and agile radiofrequency frontends for automotive applications

Vehicular connectivity serves as one of the major enabling technologies for current applications like driver assistance, safety and infotainment as well as upcoming features like highly automated vehicles - all of which having certain quality of service requirements, e. g. datarate or reliability. This work focuses on vehicular integration of multiple-input-multiple-output (MIMO) capable multielement antenna systems and frequency-agile radio frequency (RF) front ends to cover current and upcoming connectivity needs. It is divided in four major parts. For each part, mostly physical layer effects are analyzed (any performance lost on physical layer, cannot be compensated in higher layers), sensitivities are identified and novel concepts are introduced based on the status-quo findings.Fahrzeugvernetzung dient als eine der wesentlichsten Befähigungstechnologien für moderne Fahrerassistenzsysteme und zukünftig auch hochautomatisiertes Fahren. Sowohl die heutigen als auch zukünftige Anwendungen haben besondere Dienstgüteanforderungen, z.B. in Bezug auf die Datenrate oder Verlässlichkeit. Im Rahmen dieser Arbeit wird die Integration von Mehrantennensystemen für MIMO-Funkanwendungen (MIMO: engl. Multiple Input Multiple Output) sowie von frequenzagilen Hochfrequenzfrontends im Fahrzeugumfeld untersucht, um so eine technische Grundlage für zukünftige Anforderungen an die automobile Vernetzung anbieten zu können. Die dabei gewonnenen Erkenntnisse lassen sich in vier Teile gliedern. Grundsätzlich konzentrieren sich die Untersuchungen vorrangig auf die physikalische Ebene. Auf Basis des aktuellen Status Quo werden Sensitivitäten herausgearbeitet, neue Konzepte hergeleitet und entwickelt

Optics for AI and AI for Optics

Artificial intelligence is deeply involved in our daily lives via reinforcing the digital transformation of modern economies and infrastructure. It relies on powerful computing clusters, which face bottlenecks of power consumption for both data transmission and intensive computing. Meanwhile, optics (especially optical communications, which underpin today’s telecommunications) is penetrating short-reach connections down to the chip level, thus meeting with AI technology and creating numerous opportunities. This book is about the marriage of optics and AI and how each part can benefit from the other. Optics facilitates on-chip neural networks based on fast optical computing and energy-efficient interconnects and communications. On the other hand, AI enables efficient tools to address the challenges of today’s optical communication networks, which behave in an increasingly complex manner. The book collects contributions from pioneering researchers from both academy and industry to discuss the challenges and solutions in each of the respective fields