Novel theoretical formulations and efficient simulation methods for polarization-mode dispersion (PMD) and polarization-dependent loss (PDL) that are directly applicable to optical network design are developed. In particular, a formalism based upon the Magnus expansion is advanced for the determination of the frequency evolution of the Mueller matrix in terms of increasing orders of PMD and PDL. Several previous models of polarization evolution are shown to be specializations of this more general formalism. A least-squares algorithm that extracts PMD and PDL coefficients from repeated measurements of the output Stokes vector of an optical system for a random set of input polarization states is introduced and subsequently applied to the rapid experimental determination of the probability density of the differential group delay of a fiber-squeezer based PMD emulator. The applicability of Clifford algebra and Pade-approximant techniques to the efficient simulation of the wavelength dependence of PMD and PDL is also discussed.

This thesis firstly theoretically describes phenomena which appear in optical fiber transmission. The theoretical part of the thesis deals with linear and non-linear phenomena, and later on proceeds to dispersions with a more significant effect on the optical transmission quality. It puts polarization to the centre of the phenomenon called Polarization mode dispersion (PMD), which is the main object of our interest. It leads to a deep PMD description from the point of view of polarization states, limit values, compensation methods, and methods of measurement. The practical part of this thesis deals with a draft of PMD measurement via Fixed Analyzer method. For the purposes of this measurement, we used the optical spectral analyzer MS9740A. In order to compare measured values, the proposed idea then proceeds to the reference measurement by using a modular platform EXFO FTB--200 in combination with CD/PMD module EXFO FTB-5700. Results of measurements have been evaluated for the limit values defined by the standard. In the last chapter of this thesis, the reference measurements are compared to the Fixed Analyzer method. All the advantages and disadvantages of individual measurement methods are identified at the end of this chapter too.

The presence of various impairments in fiber channel has forced researchers to uncover solutions to minimize those effects. With the advancement of technology, optical solutions were finally easier to implement in the system. To this day, optical compensation methods are still found to be as the best way to minimize fiber impairments. With the development of digital signal processing (DSP) and FIR techniques, coherent detection with digital signal processing (DSP) is developed, analyzed theoretically and numerically and experimentally demonstrated in long-haul high speed fiber‐optic transmission system. The use of DSP in conjunction with coherent detection unleashes the benefits of coherent detection which rely on the preservation of full information of the transmitted field. These benefits include high receiver sensitivity, the ability to achieve high spectral‐efficiency and the use of advanced modulation formats. The local oscillator (LO) of coherent receiver alleviates the need for hardware phase‐locking and polarization tracking, which can now be achieved in the digital domain. The computational complexity previously associated with coherent detection is hence significantly diminished and coherent detection is once again considered a feasible detection alternative. In this thesis, an optical fiber communication scheme using the coherent detection method is simulated. Firstly, at the beginning of each chapter, we introduce the various compensation methods for certain optical fiber impairments which is developed by the pioneers. However, such technique does introduce enormous complexity to the system, in addition to a large cost. For that reason, the main focus had to shift to an alternative method. DSP techniques has enabled simple techniques to mitigate various impairments in fiber-optical systems. In this thesis, the background knowledge about the structure of fiber-optical transmission system is provided. After the mathematical analysis of the various impairments (laser noise, chromatic dispersion, polarization mode dispersion and nonlinearity) in fiber-optical links, the compensation methods by using DSP techniques are provided. By the methods of fourth-power carrier recovery algorithm and feedforward carrier recovery algorithm, the phase rotation in constellation due to laser noise is compensated in QPSK systems and QAM systems, respectively. The feedforward carrier recovery algorithm has a high tolerance for laser linewidth in high-order QAM system. As for PMD compensation, on the basis of adaptive equalizers in both time domain and frequency domain achiever by the pioneers, a novel LMS algorithm is proposed in this thesis. It has a fair comparative and steady computational complexity with the increase in the number of training blocks. The last part is the nonlinearity compensation. The DBP compensation is a popular method for nonlinearity compensation but its computational complexity is fair high (Shao J, Kumar S and Liang X., 2013). We adopt two kinds of fold-DBP which are distance-folded DBP and dispersion-folded DBP to compensate the joint impairments of chromatic dispersion and nonlinearity in dispersion-managed system. The distance-folded DBP works well in the full compensation dispersion-managed system but in the presence of RDPS, only the dispersion-folded DBP is efficient. / Thesis / Master of Applied Science (MASc)

In dieser Arbeit werden verschiedene Methoden zur Erhöhung der Systemtoleranz optischer Übertragungssysteme theoretisch analysiert, durch numerische Simulationen untersucht und in Experimenten und Feldversuchen praktisch überprüft. Der Schwerpunkt lag dabei auf empfängerseitigen elektronischen sowie optischen Entzerrern. Diese Entzerrer verbessern die Signalübertragung, in dem sie die Augenöffnung des Signals am Empfänger vergrößern oder in dem sie durch digitale Logikschaltungen das gesendete Signal aus einem gestörten Signal rekonstruieren. Der Schwerpunkt dieser Arbeit liegt jedoch auf der Untersuchung der Entzerrer auf Systemebene, d.h. es wird das Verhalten in einem kompletten optischen Übertragungssystem bestehend aus Sender, Glasfaserstrecke und Empfänger bewertet. Zur Untersuchung wurde eine Simulationsumgebung in der Programmiersprache FORTRAN erstellt, in der die unterschiedlichen Entzerrer in verschiedenen Netz-Szenarien untersucht wurden. Zur praktischen Untersuchung wurde außerdem eine Testumgebung im verlegten Glasfasernetz aufgebaut und eine Realisierung eines Entzerrers experimentell untersucht. / In this thesis, several methods for the enhancement of the tolerance of optical transmission systems are analyzed theoretically, investigated in numerical simulations and evaluated in experiments and field trials. The investigations were thereby focused on receiver sided electronic and optical equalizers. Those devices improve the signal transmission by increasing the eye-opening at the receiver or by reconstructing the original signal from the distorted received signal by the use of digital signal processing. However, this thesis is focused on the investigation of different equalizers on a system level where the performance of a complete transmission system consisting of a transmitter, transmission fiber and receiver is evaluated. For those studies a simulation environment was created using the programming language FORTRAN where the different equalizers were evaluated in different network scenarios. For practical investigations, a test environment was created using the deployed fiber infrastructure and specific equalizer realization were evaluated experimentally.

No description available.

My graduation thesis is concerned with the effect of polarization mode dispersion on transmitted signal by optical line. It describes external and internal causes of origination of polarization mode dispersion. On the basis of these effects there is a differential group delay (DGD). It is the time delay in meantime within individual modes. DGD results in a time extension of impulsion and limitation of maximum bit rate. This thesis contains localization methods of part of gossamer filament with increased value of PMD by POTDR method. This method is based on the principium of back dispersion and its modifications SOP a DOP. Very important chapter of this thesis is the measurement of the polarization mode dispersion. There are described methods of PMD measurement. It is the interferometric and polarimetric method and the method of state of polarization. The major part of this thesis is about the reduction of polarization mode dispersion effect. This part is divided into two parts. First part is about the methods of PMD effect reduction and the second one is about the PMD compensation. The discrepancy between these two parts is the reduction way of PMD effect on transmitted channel. The compensation use the compensation components inserted into the transmission path. By PMD reduction methods we can solve the problems from the view of changing of fibre or all cable. For better understanding of polarization mode dispersion effect there are simulated 4 optical lanes of various parameters. The simulation output is the eye diagram which provides the view at results of transmission lane. In the final part there is the evaluation of measured parameters of optical lanes simulated in a laboratory.

In dieser Arbeit werden verschiedene Methoden zur Erhöhung der Systemtoleranz optischer Übertragungssysteme theoretisch analysiert, durch numerische Simulationen untersucht und in Experimenten und Feldversuchen praktisch überprüft. Der Schwerpunkt lag dabei auf empfängerseitigen elektronischen sowie optischen Entzerrern. Diese Entzerrer verbessern die Signalübertragung, in dem sie die Augenöffnung des Signals am Empfänger vergrößern oder in dem sie durch digitale Logikschaltungen das gesendete Signal aus einem gestörten Signal rekonstruieren. Der Schwerpunkt dieser Arbeit liegt jedoch auf der Untersuchung der Entzerrer auf Systemebene, d.h. es wird das Verhalten in einem kompletten optischen Übertragungssystem bestehend aus Sender, Glasfaserstrecke und Empfänger bewertet. Zur Untersuchung wurde eine Simulationsumgebung in der Programmiersprache FORTRAN erstellt, in der die unterschiedlichen Entzerrer in verschiedenen Netz-Szenarien untersucht wurden. Zur praktischen Untersuchung wurde außerdem eine Testumgebung im verlegten Glasfasernetz aufgebaut und eine Realisierung eines Entzerrers experimentell untersucht.:Inhaltsverzeichnis 1 Einleitung 1 2 Grundaufbau und Komponenten optischer Übertragungssysteme 3 2.1 Optische Sender 4 2.2 Das Übertragungsmedium Glasfaser 9 2.3 Optische Faserverstärker 22 2.4 Optische Empfänger und Signalauswertung 24 3 Filterstrukturen und Polynomsysteme 29 3.1 Digitalfilter 29 3.2 Optische Filter 30 3.3 Volterra-Systeme 33 4 Elektronische Entzerrung zur Erhöhung der Systemtoleranz 35 4.1 Klassische Entzerrer 35 4.2 Nichtlineare Entzerrer basierend auf Volterra-Systemen 41 4.3 Maximum Likelihood Sequence Estimation 45 5 Optische Entzerrung und Kompensation 49 5.1 Dispersionskompensationsfasern 49 5.2 Optische FIR-Filter 50 6 Entzerrung in unkompensierten Übertragungssystemen 61 6.1 Prinzipieller Vergleich der Entzerrer bei linearer Übertragung 61 6.2 Entzerrung unter Berücksichtigung nichtlinearer Fasereffekte 78 7 Entzerrung in dispersionskompensierten Übertragungssystemen 87 7.1 Ausgleich einer DCF-Fehlanpassung 87 7.2 Entzerrung von Restdispersion 93 8 Gleichzeitige Entzerrung mehrerer Fasereffekte 97 8.1 Simulation der Entzerrung durch MLSE-Entzerrer 97 8.2 Experimentelle Untersuchung von MLSE-Entzerrern im Feldversuch 99 9 Alternative Verfahren zur Erhöhung der Systemtoleranz 113 9.1 Optisches Subcarrier-Multiplexing 113 9.2 Gezielter Austausch von Glasfasern mit hoher PMD 117 10 Zusammenfassung und Schlussfolgerung 121 Literaturverzeichnis 123 Verzeichnis der im Rahmen dieser Arbeit entstandenen Veröffentlichungen 133 Anhang A 137 Anhang B 138 / In this thesis, several methods for the enhancement of the tolerance of optical transmission systems are analyzed theoretically, investigated in numerical simulations and evaluated in experiments and field trials. The investigations were thereby focused on receiver sided electronic and optical equalizers. Those devices improve the signal transmission by increasing the eye-opening at the receiver or by reconstructing the original signal from the distorted received signal by the use of digital signal processing. However, this thesis is focused on the investigation of different equalizers on a system level where the performance of a complete transmission system consisting of a transmitter, transmission fiber and receiver is evaluated. For those studies a simulation environment was created using the programming language FORTRAN where the different equalizers were evaluated in different network scenarios. For practical investigations, a test environment was created using the deployed fiber infrastructure and specific equalizer realization were evaluated experimentally.:Inhaltsverzeichnis 1 Einleitung 1 2 Grundaufbau und Komponenten optischer Übertragungssysteme 3 2.1 Optische Sender 4 2.2 Das Übertragungsmedium Glasfaser 9 2.3 Optische Faserverstärker 22 2.4 Optische Empfänger und Signalauswertung 24 3 Filterstrukturen und Polynomsysteme 29 3.1 Digitalfilter 29 3.2 Optische Filter 30 3.3 Volterra-Systeme 33 4 Elektronische Entzerrung zur Erhöhung der Systemtoleranz 35 4.1 Klassische Entzerrer 35 4.2 Nichtlineare Entzerrer basierend auf Volterra-Systemen 41 4.3 Maximum Likelihood Sequence Estimation 45 5 Optische Entzerrung und Kompensation 49 5.1 Dispersionskompensationsfasern 49 5.2 Optische FIR-Filter 50 6 Entzerrung in unkompensierten Übertragungssystemen 61 6.1 Prinzipieller Vergleich der Entzerrer bei linearer Übertragung 61 6.2 Entzerrung unter Berücksichtigung nichtlinearer Fasereffekte 78 7 Entzerrung in dispersionskompensierten Übertragungssystemen 87 7.1 Ausgleich einer DCF-Fehlanpassung 87 7.2 Entzerrung von Restdispersion 93 8 Gleichzeitige Entzerrung mehrerer Fasereffekte 97 8.1 Simulation der Entzerrung durch MLSE-Entzerrer 97 8.2 Experimentelle Untersuchung von MLSE-Entzerrern im Feldversuch 99 9 Alternative Verfahren zur Erhöhung der Systemtoleranz 113 9.1 Optisches Subcarrier-Multiplexing 113 9.2 Gezielter Austausch von Glasfasern mit hoher PMD 117 10 Zusammenfassung und Schlussfolgerung 121 Literaturverzeichnis 123 Verzeichnis der im Rahmen dieser Arbeit entstandenen Veröffentlichungen 133 Anhang A 137 Anhang B 138

This doctoral thesis deals with present trend to turn up the bit rate of the optical fibres making use of wavelenght multiplex systems. There are new theoretical and practical problems caused by the new technologies. Except the known modal dispersion there exist problems caused by chromatical and polarization mode dispersion. In the opening of the thesis the known effects, which influence the payload signal, are introduced. The polarization mode dispersion has the main attention. Within the scope of this thesis there has been programmed the statistical calculator which can analyses the measured values of differential group delay by Monte Carlo calculation. Next meaningful output is the designating application of the optical routes. It is possible to mathematicaly unambiguously define the polarization mode dispersion by Jones, Stokes and Poynting vectors. This complicated calculations are mechanized and in the simulation application make possible to simulate the signification of the PMD influence at different input parameters. The thesis includes the study of the PMD modulation format impact with the results of simulations and confrontation with other scientists results. The significant output are the final practical results examinations, which can be implemented thanks to the possibility of using the FTB-5500B measuring device.

Avec l'augmentation continue du débit par canal, les effets de déformation des impulsions sont de plus en plus critiques, comme peut l'être la dispersion modale de polarisation (PMD) pour un débit de 40 Gbit/s dans les réseaux de fibre optique actuels. Les réseaux tout optiques du futur intégreront des fonctions de conversion de longueur d'onde et de régénération tout optique au niveau des noeuds de commutation. Dans ce mémoire, nous étudions plus particulièrement la capacité des régénérateurs optiques à combattre la PMD. Si leur e cacité est averée, ils constitueront tout naturellement des compensateurs de PMD distribués dans le réseau.<br />Après une introduction aux systèmes de télécommunications par fibre optique et au phénomène de dispersion modale de polarisation, nous présentons les techniques de régénération du signal. Nous proposons une méthode originale pour caractériser un régénérateur optique vis-à-vis de la PMD et en déduire la probabilité de coupure d'une liaison avec un régénérateur d'une part, et sa place optimale au sein de la liaison d'autre part.<br />Les régénérateurs 2R peuvent être classés en deux catégories : les régénérateurs de type I traitent les impulsions sans leur donner de forme particulière tandis que les régénérateurs de type II donnent une forme bien spécifique aux impulsions. L'étude numérique de la capacité d'un régénérateur de type I à combattre la PMD en un passage unique met en évidence l'inutilité d'un régénérateur placé directement devant le récepteur. Seul un régénérateur déporté au sein de la ligne de transmission permet de compenser la PMD dans une certaine mesure, et son e cacité est maximale s'il est placé pratiquement au milieu de la liaison.<br />La technique de régénération par élargissement spectral et fltrage décalé constitue un bon exemple de régénérateur de type II. Par son principe même, ce type de régénérateur permet une compensation naturelle de la PMD. Mais son étude approfondie théorique et expérimentale démontre son inefficacité pour combattre la PMD en un passage.<br />Ces travaux se concluent par l'étude de l'impact de la PMD sur les techniques de récupération d'horloge électriques ou optiques, élément clé de tout régénérateur 3R et de tout récepteur. Les techniques électroniques simples ne peuvent être employées en raison du creusement du spectre électrique induit par la PMD et du décalage temporel horloge-données créé. Aussi l'utilisation de techniques de récupération d'horloge tout optiques permet de circonvenir ces deux limitations. En particulier, les lasers auto-pulsants constituent des composants très prometteurs pour réaliser une récupération d'horloge optique en présence de PMD. Enfin leur utilisation dans un régénérateur 3R original permet de démontrer la faisabilité d'une compensation de la PMD par un régénérateur 3R tout optique à architecture simple.

En els últims anys la importància de la polarització en les comunicacions òptiques ha crescut notablement com resultat de tres grans desenvolupaments:1. L'aparició de l'amplificació òptica ha fet que es produeixi un gran increment en les longituds dels enllaços de fibra monomode, així com en el nombre de dispositius òptics que ha de travessar la llum sense regenerar-se. Com a resultat d'això, petits efectes com la diferència de retards entre els modes amb polaritzacions ortogonals, o petites diferències entre les pèrdues d'inserció per a aquests modes, poden acumular-se a causa de la gran distància a recórrer, esdevenint un paràmetre a considerar en el disseny dels sistemes.2. La possibilitat de la detecció coherent en la qual el receptor és sensible al batut de dos feixos de llum i no només a la potència del feix, ha dut també a haver de considerar el tractament de la polarització com un dels punts d'investigació importants.3. L'última raó per la qual la polarització s'ha convertit en un tema fonamental és l'impressionant increment que s'ha donat en les velocitats de transmissió, que de nou duu que petits efectes es tornin importants per l'extremadament petit temps de bit.L'estructura no perfectament cilíndrica de la fibra òptica durà a les diferents components transversals dels camps a veure índexs de refracció lleugerament diferents, amb el que es produirà acoblament d'energia d'un mode a l'ortogonal i diferències de retard entre els modes. Les imperfeccions de la fibra no són predictibles (les seves causes van des de la pròpia fabricació fins als esforços als que es vegi sotmesa després de la seva instal·lació) pel que es fa difícil una caracterització del problema. Es tractarà d'un fenomen estadístic pel que no es pot solucionar de forma determinista. Aquest treball s'emmarca dintre de l'àmbit de la recerca de solucions als efectes provocats per la polarització en els sistemes de comunicacions per fibra òptica. Els objectius marcats inicialment es van circumscriure a la detecció coherent. L'objectiu fonamental era l'estudi de les diverses tècniques per a solucionar els esvaïments per desadaptació de les polaritzacions en aquest tipus de receptors. No obstant això, en el treball que es presenta s'han inclòs també realitzacions encaminades als sistemes MI-DD, cap a les quals s'han bolcat els nostres esforços durant el període de durada del mateix. Encara que es tracta de filosofies totalment distintes, pràcticament totes les realitzacions pensades per als sistemes coherents podran aplicar-se també als sistemes MI-DD pel que no ha de pensar-se en aplicacions excloents.Les parts en que es divideix el treball són: · Estudi analític de la variació de la polarització de la llum en fibres òptiques. Dintre d'aquesta part s'oferixen resultats que es corresponen amb mesures realitzades sobre fibra i simulacions del comportament de la mateixa, i representen la justificació de tot el treball posterior.· Estudi de les diferents solucions al problema de la polarització en els receptors coherents. Es presenten aquí tots els dispositius dissenyats i construïts així com els diferents algorismes proposats per al control de la polarització. S'exposen tanmateix les mesures realitzades per a la caracterització d'aquests dispositius i la seva integració en un receptor coherent real.· Estudi dels efectes de la polarització en els sistemes MI-DD d'última generació i aplicació dels dispositius dissenyats en aquest tipus de sistemes. En aquesta part s'oferixen algunes prediccions sobre els valors que pot prendre la dispersió deguda a la polarització en enllaços reals. Així mateix es proposa un aleatorizador de la polarització amb aplicació en sistemes amb amplificació òptica. / El trabajo desarrollado en esta tesis doctoral se enmarca dentro del ámbito de la búsqueda de soluciones a los efectos provocados por la polarización en los sistemas de comunicaciones por fibra óptica tanto Coherentes como de Modulación de Intensidad y Detección Directa. El objetivo fundamental es el estudio de diversas técnicas para solucionar los problemas que los efectos de la polarización provocan en dichos sistemas como por ejemplo, los desvanecimientos por desadaptación de las polarizaciones en receptores de detección coherente o la dispersión debida a la polarización (PMD) en los sistemas MI-DD de última generación.Las partes en que se divide el trabajo son:- Estudio analítico de la variación de la polarización de la luz en fibras ópticas.Dentro de esta parte se ofrecen resultados que se corresponden con medidas realizadas sobre fibra y simulaciones del comportamiento de la misma y representan la justificación de todo el trabajo posterior.- Estudio de las diferentes soluciones al problema de la polarización en los receptores coherentes. Se presentan aquí todos los dispositivos diseñados y construidos así como los diferentes algoritmos propuestos para el control de la polarización. Se exponen asimismo las medidas realizadas para la caracterización de los mismos y su integración en un receptor coherente real.- Estudio de los efectos de la polarización en los sistemas MI-DD de última generación y aplicación de los dispositivos diseñados a su solución. En esta parte se ofrecen algunas predicciones sobre los valores que puede tomar la dispersión debida a la polarización en enlaces reales. Asimismo se propone un aleatorizador de la polarización con aplicación en sistemas con amplificación óptica. / Polarization related topics have gained momentum during last years in the optical communications field, due to the advent of three main developments:1. Optical amplification has allowed a great increase in the singlemode fiber lengths, as well as in the number of optical devices that the light must cross without being regenerated. As a result, small effects like the difference of propagation delays between the orthogonal modes, or the small differences between the insertion losses for those modes, can be accumulated due to the great distance, becoming a parameter to consider in the systems design.2. The optical coherent detection, where the receiver is sensitive to the beat of two light beams and not only to the optical power level, has also lead to take into account the light polarization as an increasingly important topic of research, as a mismatch in beams polarizations implies no signal found after the coherent detection.3. Last reason for the high importance of polarization stems from the impressive increase in bit rates that optical communications have experienced. This implies that small effects which could be neglected at lower bit rates appear now as important due to the extremely low bit periods.Therefore, it is clear that in the present and future systems the problems related to the polarization are one of the stumbling blocks to save. The origin of the polarization effects in fibers resides in their non-ideal performance. The not perfectly cylindrical structure of the optical fiber will lead the orthogonal components of the fields to see slightly different refractive indices, and so coupling of energy between modes, as well as different delays will take place. The imperfections of the fiber are not predictable (their causes go from the own manufacture to the stress applied after its installation) reason why a characterization of the problem becomes difficult. It is a statistical phenomenon, so it is not possible to be solved in a deterministic form.This work focuses on the search of solutions to the effects brought about the polarization in optical fiber communications systems. The objectives were initially confined to coherent detection systems. The main target was the study of the diverse techniques to solve the fadings by polarizations mismatch in this type of receivers. Nevertheless, solutions focusing on IM-DD systems have also been included in this work. Even considering that the approaches are very different, the different solutions thought for coherent systems can find their place in IM-DD systems.This work is divided in three parts:· Analytical study of the variation of the light polarization in optical fibers. Within this part results are offered that correspond to measures and simulations realised on fibers characterizing their behaviour. These results give reason for the remaining work.· Study of the different solutions about the polarization problem in coherent receivers. All the devices designed and constructed, as well as the different algorithms proposed for the control of the polarization are presented in this part. The measures realised for their characterization and their integration in an actual coherent receiver are also shown.· Study of the polarization effects in advanced MI-DD systems, and application of the devices designed to overcome polarization related problems. In this part some predictions are offered on the values that can take the dispersion due to the polarization in real links. Also a polarization scrambler to be used in systems with optical amplification has been designed, constructed and tested.