Τα σύγχρονα παθητικά οπτικά δίκτυα (PONs) αποτελούν ίσως την πιο σημαντική επιλογή για την ανάπτυξη των μελλοντικών δικτύων ευρυζωνικής πρόσβασης στο παρόν και το μέλλον. Κύριοι λόγοι είναι το χαμηλό κόστος εφαρμογής τους, η απλή λειτουργία τους και υψηλά ποσοστά-ρυθμού μετάδοσης. Τα σύγχρονα Ethernet Passive Optical Networks (EPONs) και η εξέλιξή τους τα Gigabit PON (XGPON) έχουν τυποποιηθεί σε ταχύτητες της τάξεως των 10 Gb/s, ενώ τα επερχόμενα πρότυπα αναμένεται να αυξήσουν τη διαθέσιμη δυναμικότητα τους. Τα EPONs, ειδικότερα, καθιστούν δυνατή τη σύγκλιση των Ethernet δικτύων μεταξύ τους, η οποία βρίσκει ευρεία εφαρμογή σε τοπικά (local) και μέτρo (metro) δίκτυα περιοχής, και την υποδομή οπτικών ινών που εγκαθίσταται εντός του πεδίου εφαρμογής σε fiber-to-the-home (FTTH), την fiber-to-the-building (FTTB) και fiber-to-the-curb (FTTC) δίκτυα. Ακόμα όμως και για πρόσβαση μέχρι τους τελικούς χρήστες. Προτείνουμε ,μέσα από την παρούσα εργασία, μια νέα μέθοδο πρόβλεψης της κυκλοφορίας με σκοπό την ελαχιστοποίηση της καθυστέρησης πακέτων σε Ethernet Passive Optical Networks (EPON). Η μέθοδος βασίζεται στην παρακολούθηση της κυκλοφορίας στο Μονάδων Οπτικού Δικτύου (ONUs) και χρησιμοποιεί τις άμεσα διαθέσιμες πληροφορίες για την κυκλοφορία του δικτύου ώστε να προβλέψει τα δεδομένα που πρόκειται να συσσωρευτούν σε κάθε ONU στον επόμενο κύκλο. Έπειτα από σχετική έρευνα υλοποιήθηκε ο κατάλληλος αλγόριθμος και εξετάστηκε πειραματικά. Τα αποτελέσματα της προσομοίωσης δείχνουν ότι η βελτίωση της καθυστέρησης διάδοσης πακέτων (delay) μειώθηκε πάνω από 25% , χωρίς τροποποίηση του υπάρχοντος αλγορίθμου ανάθεσης εύρους ζώνης. Τέλος αποδείχθηκε η δικαιοσύνη (fairness) του αλγορίθμου στην παροχή πόρων του συστήματος ανάμεσα στις μονάδες ONU. / Modern passive optical networks (PONs) are perhaps the most important choice for the development of future broadband network in the present and the future . Main reason is the low cost of implementation, simple operation and high - transmission rate . Modern Ethernet Passive Optical Networks (EPONs) and the evolution of the Gigabit PON (XGPON) have standardized speeds of 10 Gb / s, while the upcoming standards expected to increase the available capacity . The EPONs, in particular , enable the convergence of Ethernet networks , which finds wide application in locally (local) and metro (metro) area networks , and fiber optic infrastructure installed within the scope of a fiber-to-the -home (FTTH), the fiber-to-the-building (FTTB) and fiber-to-the-curb (FTTC) networks . But even for access to the end users . We propose , through this work , a new prediction method of traffic in order to minimize the delay packets in Ethernet Passive Optical Networks (EPON). The method is based on monitoring the traffic on the Optical Network Units (ONUs) and uses readily available information about network traffic to provide the data to be accumulated at each ONU in the next cycle . After investigation, the appropriate algorithm was implemented and tested experimentally. Simulation results show that the improvement of packet propagation delay (delay) fell over 25 % , without modifying the existing bandwidth assignment algorithm . Finally turned justice (fairness) algorithm in providing system resources between units ONU.

Thesis (M.Eng.). / Written for the Dept. of Electrical and Computer Engineering. Title from title page of PDF (viewed 2008/07/29). Includes bibliographical references.

Με την ανάπτυξη της τεχνολογίας οπτικών ινών κατά την τελευταία δεκαετία, η υποδομή των τηλεπικοινωνιών έχει παρουσιάσει μία τρομερή ανάπτυξη στη χωρητικότητα εύρους ζώνης των δικτύων κορμού. Η ανάπτυξη αυτή ξεκίνησε με τα δίκτυα ευρείας περιοχής (WANs) που παρέχουν συνδεσιμότητα μεταξύ πόλεων μέσω των δικτύων μητροπολιτικής περιοχής (MANs), τα οποία συνδέουν τα τηλεπικοινωνιακά κέντρα των παρόχων υπηρεσιών. Ωστόσο, τα δίκτυα πρόσβασης, που εξυπηρετούν πολυάριθμους οικιακούς χρήστες, μικρές επιχειρήσεις και οργανισμούς, δεν έχουν αναπτυχθεί ανάλογα. Παρόλο που η πρόσφατη ανάπτυξη των πρωτοποριακών τεχνολογιών xDSL και CaTV έχει αναβαθμίσει σημαντικά το τμήμα αυτό, οι τεχνολογίες αυτές είναι ακόμη ανεπαρκείς για να καλύψουν την ολοένα και αυξανόμενη ζήτηση εύρους ζώνης των χρηστών. Για την αντιμετώπιση αυτού του προβλήματος, οι τεχνολογίες της οπτικής ίνας μέχρι το σπίτι/το πεζοδρόμιο/το κτίριο (Fiber To The Home/Curb/Building – FTTH/FTTC/FTTB) έχουν θεωρηθεί από καιρό ως μια προτιμώμενη λύση και τα παθητικά οπτικά δίκτυα (PONs) θεωρούνται ευρέως ως μία πολλά υποσχόμενη τεχνολογία για την εφαρμογή διάφορων λύσεων FTTx. Η παρούσα διπλωματική εργασία αρχικά εισάγει το πρόβλημα σχετικά με την ανάγκη εφαρμογής οπτικών δικτύων πρόσβασης. Στη συνέχεια, εξετάζει πιθανές λύσεις στο πρόβλημα αυτό και αναδεικνύει τα παθητικά οπτικά δίκτυα (PONs) ως την καλύτερη επιλογή. Επιπλέον, γίνεται αναφορά στις διάφορες τεχνολογίες πολλαπλής πρόσβασης στα PONs (TDMA, OCDMA και WDMA). Η εφαρμογή της TDMA τεχνολογίας στα PONs αποδεικνύεται η πιο οικονομικά αποδοτική. Για τη χρήση της TDMA τεχνολογίας στα PONs αναπτύχθηκαν τα πρότυπα ATM PON (BPON), Ethernet PON (EPON) και Gigabit PON (GPON). Μετά από σχετική σύγκριση των προτύπων αυτών, το EPON θεωρείται η καλύτερη επιλογή για την εφαρμογή της TDMA τεχνολογίας στα PONs. Αυτή η διπλωματική εργασία στη συνέχεια εισάγει τις θεμελιώδεις έννοιες σχετικά με τα EPONs, εξετάζει τα κύρια ζητήματα που σχετίζονται με τη διάθεση εύρους ζώνης του ανοδικού καναλιού (από τον τελικό χρήστη προς το τηλεπικοινωνιακό κέντρο) στα συστήματα EPONs και παρουσιάζει μία επισκόπηση των πιο πρόσφατων αλγορίθμων δυναμικής διάθεσης εύρους ζώνης (Dynamic Bandwidth Allocation – DBA) για ανοδικές μεταδόσεις στα EPONs. Τέλος, γίνεται περιγραφή και υλοποίηση ενός εκ των πρώτων DBA αλγορίθμων που προτάθηκαν για τη διάθεση του ανοδικού εύρους ζώνης στα EPONs, του αλγορίθμου IPACT (Interleave Polling with Adaptive Cycle Time – IPACT). Κατά την περιγραφή, η limited service του αλγορίθμου IPACT προκύπτει ως η καλύτερη, με βάση διάφορα κριτήρια, μεταξύ των διάφορων υπηρεσιών αυτού του DBA αλγορίθμου και αποτελεί σημείο αναφοράς για μεταγενέστερες δημοσιευμένες εργασίες που υπάρχουν στη βιβλιογραφία. Η υλοποίηση περιλαμβάνει προσομοίωση της limited service του αλγορίθμου IPACT με χρήση της γλώσσας προσομοίωσης SIMSCRIPT II.5 και εξαγωγή αναλυτικών αποτελεσμάτων από εξισώσεις που μοντελοποιούν τη συμπεριφορά του αλγορίθμου, με χρήση της γλώσσας προγραμματισμού C. Τα αποτελέσματα της ανάλυσης και της προσομοίωσης συγκρίνονται και προκύπτουν τα κατάλληλα συμπεράσματα. / With the development of fiber-optic technology over the last decade, the telecommunications infrastructure has shown a tremendous growth in the bandwidth capacity of backbone networks. This development began with the wide area networks (WANs) that provide connectivity between cities through the metropolitan area networks (MANs), which connect service providers’ central offices. However, access networks that serve numerous residential users, small businesses and organizations have not been developed accordingly. Although the recent development of innovative xDSL and CaTV technologies has significantly upgraded this segment, these technologies are still inadequate to meet the ever-increasing bandwidth demand of users. To address this problem, fiber to the home / curb / building (FTTH / FTTC / FTTB) technologies have long been regarded as a preferred solution, and passive optical networks (PONs) are widely regarded as a promising technology for implementing various FTTx solutions. This thesis first introduces the problem concerning the need for optical access networks. Then, examines possible solutions to this problem and highlights the passive optical networks (PONs) as the best option. Furthermore, a reference is made to the various multiple access technologies in PONs (TDMA, OCDMA and WDMA). The implementation of the TDMA technology in PONs proved the most cost-effective. The ATM PON (BPON), Ethernet PON (EPON) and Gigabit PON (GPON) standards have been developed for the use of the TDMA technology in PONs. Upon comparison of these standards, the EPON is considered the best option for the implementation of the TDMA technology in PONs. This thesis then introduces the fundamental concepts on EPONs, examines the major issues related to bandwidth allocation of the upstream channel (from the end user to the central office) in EPONs systems and presents a survey of the most recent dynamic bandwidth allocation (DBA) algorithms for upstream transmissions in EPONs. Finally, a description and an implementation are made of one of the first DBA algorithms proposed for upstream bandwidth allocation in EPONs, the IPACT (Interleave Polling with Adaptive Cycle Time - IPACT) algorithm. In the description, the limited service of the IPACT algorithm emerges as the best among the different services of this DBA algorithm according to various criteria and is a benchmark for subsequent published papers in the literature. The implementation includes the simulation of the limited service of the IPACT algorithm, using the SIMSCRIPT II.5 simulation language and extraction of analytical results from equations modeling the behavior of the algorithm, using the C programming language. The analysis and simulation results are compared and the appropriate conclusions arise.

During the last three decades, the significant increase in electricity demand, and its consequences, has appeared as a serious concern for the utility companies, but no major changes have been applied to the conventional power grid infrastructure. Recently, researchers have identified efficient control and power distribution mechanisms as the immediate challenges for conventional power grids. The next step for conventional power grid towards the Smart Grid is to provide energy efficiency management along with higher reliability via smart services, in which the application of Information and Communication Technology (ICT) is inevitable. ICT introduces powerful tools to comply with the smart grid requirements. Among various ICT properties, the telecommunication network plays a key role for providing a secure infrastructure. The two-way digital communication system provides an interaction between energy suppliers and consumers for managing, controlling and optimizing energy distribution. We can also define the smart grid as a two-way flow of energy and control information, where the electricity consumers can generate energy using green energy resources. The main objective of this thesis is to select an effective data communication infrastructure to support the smart grid services by considering a hybrid wireless and optical communication technologies. Radio-over-Fibre (RoF) networks are considered as a potential solution to provide a fast, reliable and efficient network backbone with the optical access network integration and the flexibility and mobility of the wireless network. Therefore, we adopt the integration of RoF to Passive Optical Network (PON) as a broadband access network to transmit smart grid data along with the Fiber to the Home/Building/Curb (FTTx) traffic through the shared fibre, and utilizing Wavelength Division Multiplexing (WDM). Finally, we present and analyze the simulation results for the aforementioned infrastructure based on our enhanced ROF-PON integration model.

Access networks have been going through many reformations to make them adapt to arising traffic trends and become better suited for many new demanding applications. To that end, incorporating fog and edge computing has become a necessity for supporting many emerging applications as well as alleviating network congestions. At the same time, energy-efficiency has become a strong imperative for access networks to reduce both their operating costs and carbon footprint. In this dissertation, we address these two challenges in long-reach optical access networks. We first study the integration of fog and edge computing with optical access networks, which is believed to form a highly capable access network by combining the huge fiber capacity with closer-to-the-edge computing and storage resources. In our study, we examine the offloading performance under different cloudlet placements when the underlying bandwidth allocation is either centralized or decentralized. We combine between analytical modeling and simulation results in order to identify the different factors that affect the offloading performance within each paradigm. To address the energy efficiency requirement, we introduce novel enhancements and modifications to both allocation paradigms that aim to enhance their network performance while conserving energy. We consider this work to be one of the first to explore the integration of fog and edge computing with optical access networks from both bandwidth allocation and energy efficiency perspectives in order to identify which allocation paradigm would be able to meet the requirements of next-generation access networks.

This thesis puts focus on the technological challenges for Wavelength Division Multiplexed Passive Optical Network (WDM-PON) implementation, and presents novel semiconductor optical devices for deployment at the optical network unit (ONU). The first-ever reported L-band Reflective semiconductor optical amplifier (RSOA) is presented based on InP-base material. A theoretical model is developed to estimate the optical gain and the saturation power of this device compared to a conventional SOA. Experiments on this device design show long-range telecom wavelength operation, with polarization-independent gain of greater than 20 dB, and low saturation output power of 0 dBm suitable for PON applications. Next, the effect of the amplified spontaneous emission noise of RSOA devices on WDM-PON system is investigated. It is shown through theoretical modeling and simulations that the RSOA noise combined with receiver noise statistics increase probability of error, and induce considerable power penalties to the WDM-PON system. By improving the coupling efficiencies, and by distributing more current flow to the input of these devices, steps can be taken to improve device noise characteristics. Further, in spectrally-spliced WDM-PONs deploying RSOAs, the effect of AWG filter shape on system performance is investigated. Simulation modeling and experiments show that deployment of Flat-band AWGs is critical for reducing the probability of error caused by AWG spectral shape filtering. Flat-band athermal AWGs in comparison to Gaussin-shape counterparts satisfy the maximum acceptable error probability requirements, and reduce the power penalty associated with filtering effect. In addition, detuning between two AWG center wavelengths impose further power penalties to the WDM-PON system. In the last section of this thesis, motivated by RSOA device system limitations, a novel injection-locked Fabry-Perot (IL-FP) device is presented which consists of a gain section monolithically integrated with a phase section. The gain section provides locking of one FP mode to a seed source wavelength, while the phase modulator allows for adjusting the wavelength of the internal modes by tuning bias current to maintain mode-locking. This device counters any mode drifts caused by temperature variations, and allows for cooler-less operation over a wide range of currents. The devices and the performance metrics subsequently allow for a hybrid integration platform on a silicon substrate and integrate many functionalities like reflective modulator with thin film dielectric filter and receiver on a single chip for deployment at the user-end of future-proof low cost WDM-PONs.

This thesis puts focus on the technological challenges for Wavelength Division Multiplexed Passive Optical Network (WDM-PON) implementation, and presents novel semiconductor optical devices for deployment at the optical network unit (ONU). The first-ever reported L-band Reflective semiconductor optical amplifier (RSOA) is presented based on InP-base material. A theoretical model is developed to estimate the optical gain and the saturation power of this device compared to a conventional SOA. Experiments on this device design show long-range telecom wavelength operation, with polarization-independent gain of greater than 20 dB, and low saturation output power of 0 dBm suitable for PON applications. Next, the effect of the amplified spontaneous emission noise of RSOA devices on WDM-PON system is investigated. It is shown through theoretical modeling and simulations that the RSOA noise combined with receiver noise statistics increase probability of error, and induce considerable power penalties to the WDM-PON system. By improving the coupling efficiencies, and by distributing more current flow to the input of these devices, steps can be taken to improve device noise characteristics. Further, in spectrally-spliced WDM-PONs deploying RSOAs, the effect of AWG filter shape on system performance is investigated. Simulation modeling and experiments show that deployment of Flat-band AWGs is critical for reducing the probability of error caused by AWG spectral shape filtering. Flat-band athermal AWGs in comparison to Gaussin-shape counterparts satisfy the maximum acceptable error probability requirements, and reduce the power penalty associated with filtering effect. In addition, detuning between two AWG center wavelengths impose further power penalties to the WDM-PON system. In the last section of this thesis, motivated by RSOA device system limitations, a novel injection-locked Fabry-Perot (IL-FP) device is presented which consists of a gain section monolithically integrated with a phase section. The gain section provides locking of one FP mode to a seed source wavelength, while the phase modulator allows for adjusting the wavelength of the internal modes by tuning bias current to maintain mode-locking. This device counters any mode drifts caused by temperature variations, and allows for cooler-less operation over a wide range of currents. The devices and the performance metrics subsequently allow for a hybrid integration platform on a silicon substrate and integrate many functionalities like reflective modulator with thin film dielectric filter and receiver on a single chip for deployment at the user-end of future-proof low cost WDM-PONs.

abstract: Access Networks provide the backbone to the Internet connecting the end-users to the core network thus forming the most important segment for connectivity. Access Networks have multiple physical layer medium ranging from fiber cables, to DSL links and Wireless nodes, creating practically-used hybrid access networks. We explore the hybrid access network at the Medium ACcess (MAC) Layer which receives packets segregated as data and control packets, thus providing the needed decoupling of data and control plane. We utilize the Software Defined Networking (SDN) principle of centralized processing with segregated data and control plane to further extend the usability of our algorithms. This dissertation introduces novel techniques in Dynamic Bandwidth allocation, control message scheduling policy, flow control techniques and Grouping techniques to provide improved performance in Hybrid Passive Optical Networks (PON) such as PON-xDSL, FiWi etc. Finally, we study the different types of software defined algorithms in access networks and describe the various open challenges and research directions. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2015

Fault localization is the process of realizing the true source of a failure from a set of collected failure notifications. Isolating failure recovery within the network optical domain is necessary to resolve alarm storm problems. The introduction of the monitoring trail (m-trail) has been proven to deliver better performance by employing monitoring resources in a form of optical trails - a monitoring framework that generalizes all the previously reported counterparts. In this dissertation, the m-trail design is explored and a focus is given to the analysis on using m-trails with established lightpaths to achieve fault localization. This process saves network resources by reducing the number of the m-trails required for fault localization and therefore the number of wavelengths used in the network. A novel approach based on Geographic Midpoint Technique, an adapted version of the Chinese Postman’s Problem (CPP) solution and an adapted version of the Traveling Salesman’s Problem (TSP) solution algorithms is introduced. The desirable features of network architectures and the enabling of innovative technologies for delivering future millimeter-waveband (mm-WB) Radio-over-Fiber (RoF) systems for wireless services integrated in a Dense Wavelength Division Multiplexing (DWDM) is proposed in this dissertation. For the conceptual illustration, a DWDM RoF system with channel spacing of 12.5 GHz is considered. The mm-WB Radio Frequency (RF) signal is obtained at each Optical Network Unit (ONU) by simultaneously using optical heterodyning photo detection between two optical carriers. The generated RF modulated signal has a frequency of 12.5 GHz. This RoF system is easy, cost-effective, resistant to laser phase noise and also reduces maintenance needs, in principle. A revision of related RoF network proposals and experiments is also included. A number of models for Passive Optical Networks (PON)/ RoF-PON that combine both innovative and existing ideas along with a number of solutions for m-trail design problem of these models are proposed. The comparison between these models uses the expected survivability function which proved that these models are liable to be implemented in the new and existing PON/ RoF-PON systems. This dissertation is followed by recommendation of possible directions for future research in this area.

O objetivo deste trabalho é a otimização da distribuição dos divisores de potência utilizados em redes ópticas passivas, baseados na técnica de algoritmos genéticos, onde cada divisor possui uma única entrada e diversas saídas. O cenário prático de distribuição compreende uma determinada cidade, onde as ruas são as possíveis vias e as casas ou prédios são os possíveis terminais. Partindo de um ponto inicial (OLT - Optical Line Terminator), em geral a central de distribuição, chega-se aos usuários finais (ONUs - Optical Network Units) passando pelos divisores. Observa-se que temos pelo menos um ponto inicial (OLT) e diversos pontos de chegada (as ONUs) - dependendo da quantidade de saídas que o divisor óptico possui, cada uma destas representa um possível usuário ou outro divisor. O posicionamento dos divisores de potência e os caminhos utilizados que usaremos fazem parte de nossa solução. O conjunto destes elementos forma as redes de acesso óptico passivo (PON). Aspectos importantes considerados na otimização: (i) os comprimentos dos cabos desde a OLT até as ONUs, uma vez que ocorrem maiores degradações do sinal à medida que a distância aumenta, bem como aumentam os custos de implantação em proporção direta ao comprimento utilizado; e (ii) margem de potência no enlace e (iii) custo do enlace. Durante o processo de otimização, o algoritmo genético desenvolvido propõe um novo procedimento de busca de caminho denominado nó cíclico. Os resultados obtidos foram validados por comparações obtidas manualmente em redes de menor escala. Interfaces gráficas para carregamento de mapas urbanos a partir de aplicativos como Google map foram desenvolvidas. / This study, based on a genetic algorithm, optimizes the distribution of power dividers used, in the access, by passive optical networks, where each splitter has one input and several outputs. The practical scenario of distribution includes a particular city where the streets are the possible ways and the houses or buildings are the possible terminals. Starting from the OLT (Optical Line Terminal), in general the distribution center, the end users (ONUs - Optical Network Units) are connected to the OLT by a path with power divisions. Observe that we have at least one starting point (OLT) and several points of arrival (the ONUs) - depending on the amount of the optical splitter outputs, each of these representing a user. The positioning of the OLT, ONUs and power dividers are part of the solution we are seeking for and all these elements form the access passive optical network (PON). Important aspects considered: (i) the lengths of the cables from the OLT to the ONUs, once there are more signal degradation as the distance increases, (ii) link power budget and (iii) link cost. During the optimization process, the developed genetic algorithm proposes a new procedure for finding the optimum path which is called cyclic node. The obtained results have been validated by comparison with manual optimization in a smaller scale network. Graphical interfaces have been developed for uploading city maps from aplicatives Google maps.