The increasing traffic demand from the use of 3G/4G, streaming, and other broadband wireless services exposes existing bottlenecks in the communications infrastructure and the coordination between the wireless network and its wired counterpart. While wireless systems are constantly evolving to newer generations and higher capacities, their supporting wired networks urgently require advancements in both architecture design and enabling technologies. New optical access systems specifically tailored for the unique natures of various wireless standards are investigated. This dissertation presents the design and experimental verification of high-capacity optical-wireless communication systems using advanced electrical and optical technologies. Technologies such as high level modulation and multiple-input and multiple-output (MIMO) to increase the spectral efficiency is approaching the Shannon limit. New frequency bands with larger bandwidth are to be explored; for example, millimetre wave (mm-wave) spectrum range (30-300 GHz), especially the license-free spectrum located in 60 GHz. Although fiber-optic systems excel in the high-bandwidth core network, as bandwidth demand increases, more and more progress has been made towards the usage of fiber in the last mile. Radio-over-Fiber (RoF) technology has been proposed as a cost-effective optical access solution to support high-speed wireless communications, especially at the mm-wave band. Signal processing and coordination are centralized at the central office (CO), making the system economical and simple to build, operate, and maintain. Moreover, RoF systems are capable of delivering radio signals with different frequencies and protocols simultaneously. Therefore, the advantage of integrated fiber wireless systems leads to the first research topic of this dissertation: multi-band multi-service RoF systems. With an emphasis on the uniformity of the RoF platform that accommodates both legacy wireless services and advanced mm-wave services, the first part of the dissertation presents two schemes - analog all-band RoF and band-mapped 60-GHz RoF - to cover distinct application scenarios. In the all-band RoF access architecture, lower RF signals, such as Wi-Fi and cellular signals, and 60-GHz signal are transmitted at their original carrier frequencies for both indoor and outdoor coverages. On the other hand, the band-mapped mm-wave RoF scheme, fully utilizing the wide 7-GHz bandwidth at 60 GHz, delivers multiple converged high-speed services only through 60-GHz wireless link, which is especially suited for in-building broadband wireless access. The experimental verification of an all-band RoF system featuring relaxed component requirement is introduced, followed by a real-time multi-service demonstration in the proposed band-mapped 60-GHz RoF system. This dissertation also presents the design, analysis, and experimental demonstration of next-generation high-capacity cellular networks to keep up with the ever-growing bandwidth demand and performance requirements. New mobile backhaul (MBH) architectures based on orthogonal frequency division multiple access (OFDMA) are proposed along with a simple and low-latency clock distribution and recovery scheme. The transmission of OFDMA signals in the dense wavelength division multiplexing (DWDM) network with flexible clock rates and DSP-free clock recovery is implemented. Also, a spectrally-efficient, low-complexity clock distribution and recovery scheme for OFDMA-based MBH in coherent ultra-dense WDM (UDWDM) system is demonstrated. Finally, mobile fronthaul (MFH) architectures based on subcarrier multiplexing (SCM) technology, which significantly reduces the requirements on both the number of wavelengths per cell site and the optical bandwidth of the optical transceivers, are systematically investigated. Additionally, two upstream schemes, tailored for the uplink (UL), are introduced to maintain low complexity, and more importantly, to achieve high spectral efficiency by wavelength sharing. Therefore, Internet-access-oriented optical-wireless systems using Wi-Fi and other emerging mm-wave technologies are developed along with the optical fronthaul and backhaul for cellular networks in this dissertation. Moreover, with the proposed techniques, heterogeneous networks can be seamlessly provided even with different services, radio nodes, and performance requirements.

In recent years, several studies and simulations have been made on changing the current Radio Access Network (RAN) architecture into a more centralized access network where the base band processing is done in a central oce (CO) instead of out by the antenna site. This new architecture is denoted as the mobile fronthaul and is planned to be in use for the coming 5G network. The studies that have been made so far suggest that the new architecture can reduce cost, power usage and latency which are important factors regarding environmental, economical and data transmission issues. Furthermore, the new architecture allows a smarter distribution of data for each sector covered by the antennas, reducing redundant data transmission and thus increases the data eciency. The disadvantage or challenge however is that some of the optical components will be transferred from the currently controlled environment in the CO to an uncontrolled outdoor environment at the antenna site, which may generate risks as these components may be sensitive to especially changes in temperature. In this master thesis, the optical performance of four di erent passive lter setups, using a thin lm lter (TFF), an arrayed waveguide grating (AWG) and an interleaver, has been studied and compared in order to nd the most suitable lter setup for the mobile fronthaul. These optical parameters include insertion loss, isolation, crosstalk, 3 dB passband, center wavelength drift and also bit error-rate (BER) which have all been measured over a temperature interval of -40-85oC. Moreover, the measurement results have been compared with results from simulations done with VPItransmissionmaker. From the measurement results, the TFF had a better optical performance and reliability compared to the AWG mainly due to a higher isolation and a lower BER penalty of 0.2 dB compared to 0.5-1.5 dB for the AWG. Considering data capacity and economical aspects for a more realistic mobile fronthaul scenario with 80 channels using dense wavelength division multiplexing (DWDM) however, the AWG connected to the interleaver is more benecial without risking negative a ects on trac performance. / Under senare år har flera studier och simulationer utförts med syfte att ändra arkitekturen på dagens radioaccess-nätverk till ett mer centraliserat nätverk där basbandsprocesseringen sker i en central nod istället för ute vid antennen och radiomasterna. Denna nya arkitektur kallas mobile fronthaul och planeras att realiseras till 5G-nätet. De studier som har gjorts hittills indikerar på att den nya arkitekturen kan minska ekonomiska kostnader, elanvändningen och latens vilka är viktiga faktorer som bland annat rör miljö-, ekonomi och kapacitetrelaterade områden. Dessutom kan data fördelas på ett smartare sätt över alla delområden som antennerna täcker vilket minskar redundant datatrafik och därmed ökar den effektiva mängden data som skickas ut. Problemet eller utmaningen är att vissa optiska komponenter behöver flyttas från en nuvarande kontrollerad miljö till en okontrollerad utemiljö vid radiomasterna vilket kan medföra risker då dessa komponenter främst kan vara väldigt temperaturkänsliga. Inom detta examensarbete har optisk prestanda studerats, analyserats och jämförts mellan fyra olika filterkonstellationer bestående av ett tunnfilmsfilter, ett AWG-filter och en interleaver med syfte att finna vilken konstellation som passar bäst för mobile fronthaularkitekturen. De optiska parametrarna består av insertionsförluster, isolation, överhörningsinterferens, 3 dB-passband, centervåglängdsdrift samt bitfelsgrad vilka alla har blivit undersökta över ett temperaturintervall på -40-85oC. Utöver detta så har mätresultaten jämförts med simulationer gjorda med VPItransmissionmaker. Utifrån mätresultaten kunde det konstateras att tunnfilmfiltret hade bättre optiska egenskaper och även högre trovärdighet jämfört med AWG-filtret främst på grund av en högre isolation och lägre bitfelsgradsstraff på 0.2 dB jämfört med 0.5-1.5 dB för AWG-filtret. Om en endast avväger datakapacitet och ekonomiska aspekter för ett mer realistiskt scenario för mobile fronthaul med 80 DWDM-kanaler så är AWG-filtret tillsammans med interleavern mer foördelaktig att välja utan att riskera några negativa påverkningar på trafikprestandan.

[pt] Para suportar os requisitos das redes móveis de 5a geração (5G), os sistemas de comunicação óptica serão usados nas redes de acesso. Isso ocorre porque a evolução das RAN (Radio Access Networks) incluem a centralização do equipamento mais crítico para implantar pontos de acesso móveis de baixa potência, como DAS (Distributed Antenna Systems) e Small Cells. Os serviços emergentes solicitam a implantação de tecnologias de rádio sobre fibra com ênfase na eficiência de largura de banda, eficiência energética e alta confiabilidade. Neste âmbito, um monitoramento eficiente da camada física é imperativo para a operação dessas redes. O sistema de monitoramento deve fornecer uma localização de falhas em serviço, econômico, centralizado e com impacto mínimo para a transmissão de dados. Esta tese propõe vários sistemas de monitoramento incorporado no transceptor utilizando reflectometria óptica no domínio do tempo. Os sistemas de monitoramento são testados em diferentes sistemas de transmissão de dados e arquiteturas de rede, onde é apresentada uma validação simulada e outras experimentais. / [en] In order to support the requirements for 5th generation mobile networks (5G), optical communication systems will be used in the access part of the network. This is because the evolution of radio access networks includes the centralization of the most critical equipment in order to deploy low power mobile access points, like distributed antenna systems and small cells. The emerging services call for the deployment of radio over fibre technologies with emphasis on bandwidth efficiency, energy efficiency and high reliability. Within this scope, an efficient monitoring of the physical layer would become essential for the operation of these networks. The monitoring system should provide in-service, cost efficient and centralized fault localization with minimum impact on data transmission. This thesis proposes several transceiver-embedded optical time domain reflectometry monitoring systems. The monitoring systems are tested over different data transmission systems and network architectures, where one architecture was simulated and several others experimentally validated.

Initialement poussées par le marché résidentiel, les évolutions du réseau d’accès optique sont aujourd’hui également stimulées par l’expansion du réseau mobile. Comme le montre le premier chapitre de ce document, l’introduction d’un multiplexage en longueur d’onde dense constitue l’une des solutions privilégiées pour permettre la montée en débit dans les réseaux d’accès optique. Dans cette thèse, l’impact de l’introduction du multiplexage en longueur d’onde dense est étudié sous trois axes :• Une prochaine étape de l’évolution des technologies pour les réseaux d’accès passerait par une hybridation entre d’une part, un multiplexage temporel (hérité des précédentes générations), et d’autre part, un multiplexage en longueur d’onde dense. Cette technologie, appelée NGPON2-TWDM, permet aujourd’hui d’envisager des débits de 40Gb/s à 80Gb/s grâce à 4 ou 8 canaux. Les difficultés liées à la stabilité de la longueur d’onde lors de l’émission de données en mode paquet dans le sens montant du lien, ainsi que les solutions associées, sont étudiées dans le second chapitre.• L’importance du marché que représente le réseau d’accès optique (aussi bien pour les clients résidentiels que pour les réseaux mobiles), induit la nécessité pour les différentes générations de technologies de coexister au sein d’une même infrastructure. Du fait des fortes puissances optiques en jeu et des plages spectrales allouées à chaque technologie, cette coexistence peut induire des interactions entre technologies par émission Raman stimulée, dont le principe et les impacts sont décrits dans le troisième chapitre.• Enfin, la quatrième partie de ce document est dédiée à l’étude des limites et potentialités de la technologie self-seeded pour le multiplexage en longueur d’onde dense en bande O, capable de stabiliser automatiquement et passivement la longueur d’onde d’émission de chacun des émetteurs du système. / Initially led by the residential market, today’s optical access network evolutions are stimulated by mobile network expansion. As shown in the first chapter of this document, dense wavelength division multiplexing is one of the favorite solutions in order to increase optical access networks throughput. In this thesis, we propose a study of dense wavelength division multiplexing introduction according to three main topics :• Service providers and equipment suppliers have decided that the next step in residential market evolution will consist in a hybridization between, on one hand, a legacy time division multiplexing, and on the other hand, a dense wavelength division multiplexing. Named NG-PON2, this technology allows today 40Gb/s to 80Gb/s thanks to 4 to 8 channel pairs. Wavelength stability of the upstream emitter under burst mode operation, and related solutions, are studied in the second chapter.• Market importance (for both residential market and mobile networks) requires the different technologies generations to coexist on the same infrastructure. Due to the high optical power and the wavelength spans allocated to each technology, this coexistence can lead to technologies interactions by stimulated Raman scattering, as described in the third chapter.• Finally, the fourth part of this document describes the limits and potentialities of the self-seeded emitter technology for O-band dense wavelength division multiplexing, able to automatically and passively self-stabilize the wavelength of each emitter.