The characteristics of a silicon-on-insulator (SOI) rib waveguide, including the bending loss of a multimode bent waveguide and the birefringence of a rib waveguide, are analyzed by using a finite-difference method (FDM). Based on a detailed analysis for a multimode bent waveguide, an appropriately designed multimode bent waveguide for reducing effectively the bending loss of the fundamental mode is realized. The slab height and the rib width of an SOI rib waveguide are normalized with the total height of the silicon layer and a general relation between these two normalized parameters for a nonbirefringent SOI rib waveguide is established. Using this general relation, one can easily design a nonbirefringent SOI rib waveguide. The issue of multimode effect in the SOI-based microphotonic devices such as arrayed-waveguide gratings (AWGs), etched diffraction gratings (EDGs), and multimode interference (MMI) couplers is discussed in detail. Two kinds of taper structures are proposed for reducing the multimode effects in EDGs or MMI couplers. A bi-level taper is introduced to eliminate effectively the multimode effects in an EDG or an MMI coupler. The bi-level taper is very appropriate for an EDG demultiplexer since the Si layer is etched through simultaneously for both the grating and the bottom taper structure, and thus no additional fabrication process is required. For the simulation of an AWG demultiplexer, a fast simulation method based on the Gaussian approximation is proposed and two kinds of effective and accurate three-dimensional (3D) simulation modeling are developed. The first 3D model is based on Kirchhoff-Huygens diffraction formula. To improve the computational speed, the 3D model is reduced to a two-dimensional (2D) one by integrating the corresponding field distributions in the AWG demultiplexer along the vertical direction under an assumption that the power coupled to the higher order modes in the free propagation region (FPR) is negligibly small. The equivalent 2D model has an almost the same accuracy as the original 3D model. Furthermore, a reciprocity theory is introduced for the optimal designof a special structure used for flattening the spectral response of an AWG demultiplexer. In the second 3D simulation method, we combine a beam propagation method (BPM) and the Kirchhoff-Huygens diffraction formula. In this method, a 3D BPM in a polar coordinate system is used for calculating the light propagation in the region connecting the first FPR and the arrayed waveguides, and thus the coupling coefficient of each arrayed waveguide is calculated conveniently and accurately. In the simulation of the second FPR, due to the uniform arrangement of arrayed waveguides, only several arrayed waveguides are needed in the BPM window and thus the computational efficiency is improved. / QC 20101004

[pt] As redes ópticas passivas de nova geração 2 (NG-PON2) estão estudando e considerando o WDM-PON (Wavelength-Division-Multiplexed Passive Optical Networks) como a nova arquitetura para as redes de acesso, é provável que esta arquitetura seja adotada num futuro como o padrão. No entanto, algumas instalações já foram realizadas em todo o mundo, a maior parte delas na Coréia do Sul. Com o objetivo de reduzir os custos de operação (OPEX) e garantir a qualidade do serviço (QoS) um sistema de supervisão e localização de falhas é necessário. Neste trabalho é proposto e demonstrado um OTDR sintonizável (Optical Time-Domain Reflectometer) para realizar o monitoramento de redes WDMPON em serviço. O método apresentado é provado para diferentes fontes laser sintonizáveis CW (Continuous Wave) e utiliza um amplificador óptico semicondutor (SOA) como comutador para o sinal de prova. O sistema de monitoramento é provado experimentalmente numa rede WDM-PON simulada no laboratório a qual utiliza um AWG (Arrayed Waveguide Grating) como distribuidor. Os resultados foram melhorados utilizando diferentes métodos para mitigar os efeitos de interferência. / [en] The Next Generation Passive Optical Network 2 (NG-PON2) is considering and studying wavelength-division-multiplexed passive optical networks (WDM-PONs) as the new architecture for access networks, this architecture is likely to be adopted in near future as standard. However some deployments have been achieved worldwide, most of them in South Korea. In order to lower the operational expenditure (OPEX) and guarantee quality-of-service (QoS) an in-service monitoring and fault localization system is required. We propose and demonstrate a tunable optical time-domain reflectometer (T-OTDR) for in-service monitoring of (WDM-PONs). The proposed method is proved for different continuous wave tunable laser sources (CW TLS), and uses semiconductor optical amplifier (SOA) as a switch for the probe signal. This monitoring system is experimentally proved in a simulated WDMPON employing a cyclic AWG (Arrayed Waveguide Grating) as wavelength distributor. We improve the results using different methods to mitigate the interference effects.

[ES] La presente tesis se ha centrado en el modelado, diseño y demonstración experimental por primera vez del dispositivo Reconfigurable Reflective Arrayed Waveguide Grating (R-RAWG). Para la consecución de este dispositivo que tiene posibilidades de uso en la espectrometría, una plataforma de nitruro de silicio llamada CNM-VLC se ha usado, ya que este material permite operar en un gran ancho de banda. Esta plataforma posee ciertas limitaciones y los elementos necesarios para el funcionamiento de este dispositivo tenían un performance bajo. Por ello, se ha desarrollado y validado una metodología que ha permitido obtener mejores divisores. Además, se ha diseñado un inverted taper que ha mejorado considerablemente el acoplo de luz al chip. Esto ha sido gracias a un exhaustivo análisis de opciones existentes en la literatura que también ha permitido escoger la mejor opción para realizar un espejo reconfigurable en la plataforma sin cambiar ni añadir ningún proceso de fabricación. Se han demostrado espejos reconfigurables gracias a utilizar divisores ópticos realimentados y también se ha desarrollado códigos que predicen el comportamiento del dispositivo experimentalmente. Con todo el trabajo realizado, se ha diseñado un R-RAWG para que pudiera operar en un gran ancho de banda y que los actuadores de fase no tuvieran peligro de estropearse. También se ha desarrollado un código para el modelado del R-RAWG que permite imitar la fabricación de estos dispositivos y que, gracias a esto, se ha desarrollado un método o algoritmo llamado DPASTOR, que usa algoritmos usados en machine learning, para optimizar la respuesta con tan sólo la potencia óptica de salida. Finalmente, se ha diseñado una PCB para poder conectar eléctricamente el chip fotónico y se ha desarrollado un método de medida que ha permitido tener una respuesta estable consiguiendo demostrar multitud de respuestas de filtros ópticos con el mismo dispositivo. / [CAT] La present tesi s'ha centrat en el modelatge, disseny i demonstració experimental per primera vegada del dispositiu Reconfigurable Reflective Arrayed Waveguide Grating (R-RAWG). Per a la consecució d'aquest dispositiu que té possibilitats d'ús en l'espectrometria, una plataforma de nitrur de silici anomenada CNM-VLC s'ha usat ja que aquest material permet operar en una gran amplada de banda. Aquesta plataforma posseeix certes limitacions i els elements necessaris per al funcionament d'aquest dispositiu tenien un performance baix. Per això, s'ha desenvolupat i validat una metodologia que ha permés obtindre millors divisors i també, gràcies als processos de fabricació, s'ha dissenyat un acoplador que ha millorat considerablement l'acoble de llum al xip. Això ha sigut gràcies a un exhaustiu analisis d'opcions existents en la literatura que també ha permés triar la millor opció per a realitzar un espill reconfigurable en la plataforma sense canviar ni afegir cap procés de fabricació. S'han demonstrat espills reconfigurables gràcies a utilitzar divisors realimentats i també s'ha desenvolupat codis que prediuen el comportament del dispostiu experimentalment. Amb tot el treball realitzat, s'ha dissenyat un R-RAWG fent ús de determinades consideracions perquè poguera operar en una gran amplada de banda i que els actuadors de fase no tingueren perill de desbaratar-se. També s'ha desenvolupat un codi per al modelatge del R-RAWG que permet imitar la fabricació d'aquests dispositius i que, gràcies a això, s'ha desenvolupat un mètode o algorisme anomenat DPASTOR, que usa algorismes usats en machine learning, per a optimitzar la resposta amb tan sols la potència òptica d'eixida. Finalment, s'ha dissenyat una PCB per a poder connectar elèctricament el xip fotònic i s'ha desenvolupat un mètode de mesura que ha permés tindre una resposta estable aconseguint demostrar multitud de respostes de filtres òptics amb el mateix dispositiu. / [EN] This thesis is focused on the modelling, design and experimental demonstration for the first time of Reconfigurable Reflective Arrayed Waveguide Grating (R-RAWG) device. In order to build this device, that can be employed in spectrometry, a silicon nitride platform termed CNM-VLC has been chosen since this material allows to operate in broad range of wavelengths. This platform has the necessary elements, but some limitations because the operation of this device had a low performance. Therefore, a methodology has been developed and validated, which has allowed to obtain better splitters. Also an inverted taper has been designed, which has considerably improved the coupling of light to the chip. This has been possible thanks to an exhaustive analysis of existing options in the literature, that has allowed choosing the best option to make a reconfigurable mirror on the platform without changing or adding new manufacturing steps. Reconfigurable mirrors have been demonstrated by using feedback splitters. Furthermore, codes have been developed to predict the behaviour of the actual device. With all the work done, a R-RAWG has been designed by using certain considerations so that it can operate over a broad wavelength range and the phase actuators are not in danger of being damaged. A code has also been developed for the modelling of the R-RAWG, which allows manufacturing imperfections to be considered, thanks to this, a method or algorithm called DPASTOR has been developed. DPASTOR resembles machine learning to optimise the response by just using the optical output power. Finally, a PCB and an assembly with the chip interconnected to it have been made and designed. Moreover, a measurement method has been developed, which has made it possible to have a stable response and to demonstrate a multitude of optical filter responses with the same device. / Fernández Vicente, J. (2021). Reconfigurable Reflective Arrayed Waveguide Grating on Silicon Nitride [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165783 / TESIS