Due to the tremendous growth of traffic volume caused by both exponential increase of number of Internet users and continual emergence of new bandwidth demanding applications, high capacity networks are required in order to satisfactorily handle the extremely large amount of traffic. Hence, optical fiber communication is the key technology for the network infrastructure. This thesis addresses design, analysis and simulation of access and core networks targeting important research problems, which need to be tackled for the effective realization of next generation optical networks. Among different fiber access architectures, passive optical network (PON) is considered as the most promising alternative for the last mile connection due to its relatively low cost and resource efficiency. The inherent bursty nature of the user generated traffic results in dynamically changing bandwidth demand on per subscriber basis. In addition, access networks are required to support differentiated quality of service and accommodate multiple service providers. To address these problems we proposed three novel scheduling algorithms to efficiently realize dynamic bandwidth allocation in PON, along with guaranteeing both the priority and fairness of the differentiated services among multiple users and/or service providers. Meanwhile, because of the increasing significance of reliable access to network services, an efficient fault management mechanism needs to be provided in PON. In addition, access networks are very cost sensitive and the cost of protection should be kept as low as possible. Therefore, we proposed three novel cost-effective protection architectures keeping in mind that reliability requirement in access networks should be satisfied at the minimal cost. Regarding the optical core networks, replacing electronic routers with all-optical switching nodes can offer significant advantages in realizing high capacity networks. Because of the technological limitations for realizing all-optical nodes, the focus is put on the ingenious architecture design. Therefore, we contributed on novel switching node architectures for optical circuit and packet switching networks. Furthermore, we addressed different aspects of routing and wavelength assignment (RWA) problem, which is an important and hard task to be solved in wavelength routed networks. First, we proposed an approach based on the information summary protocol to reduce the large amount of control overhead needed for dissemination of the link state information in the case of adaptive routing. In addition, transparency in optical networks may cause vulnerability to physical layer attacks. To target this critical security related issue, we proposed an RWA solution to minimize the possible reachability of a jamming attack. Finally, in order to evaluate our ideas we developed two tailor-made simulators based on discrete event driven system for the detailed studies of PON and switched optical networks. Moreover, the proposed tabu search heuristic for our RWA solution was implemented in C++. / QC 20100707

Supermassive black holes, black holes with masses <106 Msun, are found at the centers of all massive galaxies. These massive black holes grew from smaller seed black holes through accretion events. Accreting black holes are very bright in the radio through very hard X-ray spectral regimes. Due to the location of these accreting black holes at the centers of galaxies, they are referred to as active galactic nuclei (AGN). It is understood that AGN are an important phase of galaxy evolution; however, the role of AGN in massive galaxy formation is very poorly constrained. Here, the unique tool of multi-wavelength population synthesis modeling is used to study the average properties of AGN and their host galaxies with a focus on host galaxy star formation and the role of black hole growth in galaxy evolution. Knowledge of the AGN population from deep X-ray surveys is combined with theoretical AGN spectral energy distributions to predict various observables of the AGN population in wavelength regions from the far infrared to very hard X-rays. Comparison of the model predictions to observations constrains the model input parameters and allows for the determination of average properties of the AGN population. Particular attention is paid to a special class of AGN known as Compton thick AGN. These AGN are deeply embedded in gas and dust such that the column density obscuring the line of sight to the central engine of the AGN exceeds 1/σT ~ 10²⁴ cm⁻², where σT is the Thomson cross-section of the electron---a column density comparable to that of the human chest. Theoretical and simulational evidence suggest that these Compton thick AGN may be recently triggered, rapidly accreting AGN, making them of special interest to researchers. I found that Compton thick AGN are likely to contribute ~20% of the peak of the cosmic X-ray background (XRB) at ~30 keV and demonstrated that a significant portion of Compton thick AGN may be accreting very rapidly. Moreover, Compton thick AGN do not appear to follow the orientation based unified model of AGN. According to the unified model, AGN exhibit a range of obscuration levels due to a dusty 'torus' which, depending on the orientation of the torus to the observer's line of sight, may obscure the central engine of the AGN. Upon further investigation into the stellar populations of AGN host galaxies, it appears that the unified model holds in general at z < 1, but not at z > 1. I found that this is likely due to the dominant triggering mechanism of AGN switching from major mergers at z > 1.5 to secular processes by z ~ 1.

In order to fully understand the role methane (CH₄) plays in the microwave emission spectra of the deep atmospheres of the outer planets, over 280 laboratory measurements of the opacity of ammonia in a methane environment have been made in the 5-20 cm wavelength range. All opacity measurements were made with either 100 or 200 mbars of ammonia and with 1 to 3 bars of added methane in the 330-450K temperature range. A formalism for the absorptivity of ammonia broadened by methane has now been developed and had been applied to the Hanley et al. (Icarus, v. 202, 2009) model for the opacity of ammonia. Due to methane's relatively low abundance at Jupiter (~0.2% by volume), its effect on the microwave spectrum which will be observed by the Juno MWR (Microwave Radiometer) will be minimal. However, these experimental results will significantly improve the understanding of the microwave emission spectrum of Uranus and Neptune where methane plays a more dominant role.

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.

Studies demonstrate short-wavelength cone pathway dysfunction in patients with diabetes and no clinically visible DR. Poor glycemic control, as measured by hemoglobin A1c (HbA1c), is a strong risk factor for DR. We hypothesized that raised HbA1c was associated with short-wavelength cone sensitive visual evoked potential (S-VEP) and electroretinogram (sERG) dysfunction. Forty adolescents with diabetes and 39 controls were tested using the S-VEP. Latencies to a short-wavelength stimulus were delayed in patients at low contrasts. Patient S-VEP latencies were not associated with HbA1c when controlling for age and time since diagnosis. Twenty-one adolescents with diabetes and 19 controls were tested using the sERG. Implicit times of the b-wave were delayed but not associated with HbA1c when controlling for time since diagnosis.Patient PhNR amplitudes were reduced. A one-unit increase in HbA1c was associated with a 15% sERG PhNR amplitude reduction (p=0.004). The sERG PhNR may be a potential biomarker for DR.

Studies demonstrate short-wavelength cone pathway dysfunction in patients with diabetes and no clinically visible DR. Poor glycemic control, as measured by hemoglobin A1c (HbA1c), is a strong risk factor for DR. We hypothesized that raised HbA1c was associated with short-wavelength cone sensitive visual evoked potential (S-VEP) and electroretinogram (sERG) dysfunction. Forty adolescents with diabetes and 39 controls were tested using the S-VEP. Latencies to a short-wavelength stimulus were delayed in patients at low contrasts. Patient S-VEP latencies were not associated with HbA1c when controlling for age and time since diagnosis. Twenty-one adolescents with diabetes and 19 controls were tested using the sERG. Implicit times of the b-wave were delayed but not associated with HbA1c when controlling for time since diagnosis.Patient PhNR amplitudes were reduced. A one-unit increase in HbA1c was associated with a 15% sERG PhNR amplitude reduction (p=0.004). The sERG PhNR may be a potential biomarker for DR.

La ràpida evolució d’Internet i l’àmplia gamma de noves aplicacions (per exemple, multimèdia, videoconferència, jocs en línia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A més, algunes d’aquestes aplicacions demanden grans quantitats de recursos d’ample de banda amb diversos requeriments de qualitat de servei (QoS). El desenvolupament de la multiplexació per divisió de longitud d’ona (WDM) en els anys noranta va fer molt rendible la disponibilitat d’ample de banda. Avui dia, les tecnologies de commutació òptica de circuits són predominants en el nucli de la xarxa, les quals permeten la configuració de canals (lightpaths) a través de la xarxa. No obstant això, la granularitat d’aquests canals ocupa tota la longitud d’ona, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d’ona). Segons la comunitat científica, és necessari augmentar la transparència dels protocols, així com millorar l’aprovisionament d’ample de banda de forma dinàmica. Per tal de fer això realitat, és necessari desenvolupar noves arquitectures. La commutació òptica de ràfegues i de paquets (OBS/OPS), són dues de les tecnologies proposades. Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d’ona. En primer lloc, aprofundim en la naturalesa sense connexió en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a ràfega. A més, les col·lisions entre ràfegues degraden el rendiment de la xarxa fins i tot a càrregues molt baixes. Per fer front a aquestes col·lisions, es proposa un esquema de resolució de col·lisions pro actiu basat en un algorisme d’encaminament i assignació de longitud d’ona (RWA) que balanceja de forma automàtica i distribuïda la càrrega en la xarxa. En aquest protocol, el RWA i la transmissió de ràfegues es basen en l’explotació i exploració de regles de commutació que incorporen informació sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s’utilitzen dos tipus de paquets de control per a l’encaminament de les ràfegues i l’actualització de les regles de commutació, respectivament. Per analitzar els beneficis del nou algorisme, s’utilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el mètode proposat millora en diferents marges la resta d’algorismes RWA en funció de la topologia i sense penalitzar altres paràmetres com el retard extrem a extrem. La segona contribució proposa una arquitectura híbrida sense i orientada a connexió sobre la base d’un protocol de control d’accés al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos mètodes d’accés: arbitratge de cua (QA) per a la transmissió de ràfegues sense connexió, i pre-arbitratge (PA) per serveis TDM orientats a connexió. Aquesta arquitectura permet una àmplia gamma d’aplicacions sensibles al retard i al bloqueig. Els resultats avaluats a través de simulacions mostren que en l’accés QA, les ràfegues de més alta prioritat tenen garantides zero pèrdues i latències d’accés molt baixes. Pel que fa a l’accés PA, es reporta que la duplicació de la càrrega TDM augmenta en més d’un ordre la probabilitat de bloqueig, però sense afectar en la mateixa mesura les ràfegues sense connexió. En aquest capítol també es tracten dos dels problemes relacionats amb l’arquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matemàtic per aproximar el retard d’accés inferior i superior com a conseqüència de l’accés QA. En segon lloc, es formula matemàticament la generació i optimització de les topologies virtuals que suporten el protocol per a l’escenari amb tràfic estàtic. Finalment, l’última contribució explora els beneficis d’una arquitectura de xarxa òptica per temps compartit (TSON) basada en elements de càlcul de camins (PCE) centralitzats per tal d’evitar col·lisions en la xarxa. Aquesta arquitectura permet garantir l’aprovisionament orientat a connexió de canals sub-longitud d’ona. En aquest capítol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa depèn en gran mesura de l’assignació i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d’assignació de ranures temporals i es comparen amb les corresponents formulacions de programació lineal (ILP) per al cas estàtic. Per al cas de tràfic dinàmic, proposem i avaluem mitjançant simulació diferents heurístiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freqüencial a l’hora d’assignar les ranures temporals. / The rapid evolving Internet and the broad range of new data applications (e.g., multimedia, video-conference, online gaming, etc.) is fostering revolutionary changes in the way we communicate. In addition, some of these applications demand for unprecedented amounts of bandwidth resources with diverse quality of service (QoS). The development of wavelength division multiplexing (WDM) in the 90's made very cost-effective the availability of bandwidth. Nowadays, optical circuit switching technologies are predominant in the core enabling the set up of lightpaths across the network. However, full-wavelength lightpath granularity is too coarse, which results to be inefficient for provisioning sub-wavelength channels. As remarked by the research community, an open issue in optical networking is increasing the protocol transparency as well as provisioning true dynamic bandwidth allocation at the network level. To this end, new architectures are required. Optical burst/packet switching (OBS/OPS) are two such proposed technologies under investigation. This thesis contributes with three network architectures which aim at improving the sub-wavelength data transport from different perspectives. First, we gain insight into the connectionless nature of OBS. Here, the network dynamics are increased due to the short-lived burst transmissions. Moreover, burst contentions degrade the performance even at very low loads. To cope with them, we propose a proactive resolution scheme by means of a distributed auto load-balancing routing and wavelength assignment (RWA) algorithm for wavelength-continuity constraint networks. In this protocol, the RWA and burst forwarding is based on the exploitation and exploration of switching rule concentration values that incorporate contention and forwarding desirability information. To support such architecture, forward and backward control packets are used in the burst forwarding and updating rules, respectively. In order to analyze the benefits of the new algorithm, four different network topologies are used. Results indicate that the proposed method outperforms the rest of tested RWA algorithms at various margins depending on the topology without penalizing other parameters such as end-to-end delay. The second contribution proposes a hybrid connectionless and connection-oriented architecture based on a medium access control (MAC) protocol for OBS networks (DAOBS). The MAC provides two main access mechanisms: queue arbitrated (QA) for connectionless bursts and pre-arbitrated (PA) for TDM connection-oriented services. Such an architecture allows for a broad range of delay-sensitive applications or guaranteed services. Results evaluated through simulations show that in the QA access mode highest priority bursts are guaranteed zero losses and very low access latencies. Regarding the PA mode, we report that doubling the offered TDM traffic load increases in more than one order their connection blocking, slightly affecting the blocking of other connectionless bursts. In this chapter, we also tackle two of the issues related with the DAOBS architecture and its operation. Firstly, we model mathematically the lower and upper approximations of the access delay as a consequence of the connectionless queue arbitrated access. Secondly, we formulate the generation of the virtual light-tree overlay topology for the static traffic case.

A novel solid state illumination source has been developed. A two terminal dual LED has been created with the ability to control the relative intensities of the two emission peaks by varying drive current. Doping profiles have been used to extend the dynamic range of the dual LED over other reported devices. Operation of the dual LEDs is explained as a function of drive current. In addition, novel use of phosphor mixtures allows the creation of a broadband spectral power distribution that can be varied using a dual LED as an excitation source. Combinations of phosphors that have varied excitation spectra provide the ability to selectively excite different phosphors with the different LED emission peaks. First and second generations of the two terminal dual LED and the phosphor combination are discussed. The final source has the ability to mimic the light of a blackbody radiator over a range of 3200 K - 5300 K. The development of a three terminal dual LED as a pump source was prohibited by the need for a III-nitride tunnel junction, that proved unattainable in the scope of this work. However, several novel doping schemes were investigated toward this end. Finally, a circadian light source has also been developed that can affect physiological changes in humans, and a light box for entrainment of circadian rhythms in rats has been built.

This dissertation includes two parallel topics: optical modeling of wavelength converters based on semiconductor optical amplifiers (SOA) and optical modeling for LEDs and solid state lighting. A steady-state numerical model of wavelength converters based on cross-gain SOAs is developed. In this model, a new model of the gain coefficient is applied. Each physical variable, such as the carrier density, gain coefficient, differential gain, and internal loss, spatially varies across the SOA cavity and is numerically calculated throughout the device. Increased accuracy over previous studies is achieved by including such spatial variations. This model predicts wavelength-dependent characteristics of a wavelength converter of the SOA in both large and small signal regimes. Some key performance factors of SOA wavelength converters. A hybrid method incorporating both guided wave optics and optical ray tracing is also developed to model LEDs and solid state lighting. This method can model either single wavelength or dual-wavelength LED structures with different die shapes and packages. The waveguide and diffraction optics are mainly used to model the near-field optics inside LED chips and its vicinity and to identify guided modes and leakage modes. Geometrical ray tracing is applied to model the far-field pattern and light interactions at different material interfaces, such as LED chip structures, LED package materials, and light scattering at those rough surfaces and textures. To improve LED light extraction efficiency, different LED die shapes and device structures can also be optimized using this method. New technologies for future research on SOAs and LEDs are also proposed.

In response to the development of a next-generation networking (NGN) generalized multi-protocol label switching (GMPLS) technology is required for automatically switched optical network (ASON). Reconfigurable optical add-drop multiplexer (ROADM) is an indispensable device for the ASON, and the dense wavelength division multiplexed (DWDM) signals can be transmitted through the network under the management of the network administrator to configure dynamic customer needs and the desired quality of service (QoS). The ROADM can also increase the efficiency of utilizing the existing capacity of the optical fiber lines and can reduce or waive to set up additional optical fiber lines. This thesis studies a novel ROADM based on the arrayed waveguide grating (AWG) and the fiber Bragg grating (FBG) to overcome that the current ROADM cannot process that the input signal channels is greater than the wavelengths channels of AWG. Many types of ROADMs have been proposed and realized through different optical devices. Among these, hybrid optical circulator and FBG based ROADM is more attractive because of its low crosstalk and polarization insensitivity. However, it still suffers from many component counts and high insertion losses due to the use of many circulators and a multiplexer-demultiplexer pair. In this master thesis, we focus on demonstrating a novel ROADM and evaluating its crosstalk performance. It is found that the proposed ROADM has the advantage on extending the number of wavelength signal to make the system configurable and flexible.