Thesis (Ph.D.)--Victoria University (Melbourne, Vic.), 2008.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 78-80). Also available via the Internet.

Thesis (MS )--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Douglas S. Cairns. Includes bibliographical references (leaves 142-147).

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract and vita. Includes bibliographical references (leaves [132-138]).

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007. / Committee Chair: Adibi, Ali; Committee Member: Chang, Gee-Kung; Committee Member: Ralph, Stephen.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 63-65). Also available via the Internet.

Το θέμα το οποίο πραγματεύεται η παρούσα διπλωματική είναι οι αισθητήρες οπτικών ινών με φράγματα Bragg προσδιορίζοντας τον δείκτη διάθλασης του περιβάλλοντος υγρού κατά τη βύθιση του οπτικού αισθητήρα μέσα σε αυτό. Στο πρώτο κεφάλαιο θα γίνει αρχικά μια ανάλυση των οπτικών ινών αφού θα αναφερθούν ο τρόπος λειτουργίας τους, οι τύποι οπτικών ινών που υπάρχουν, πλεονεκτήματα και μειονεκτήματα που παρουσιάζουν αλλά και ο λόγος που οδηγήθηκε η τεχνολογία στην κατασκευή τους. Στο δεύτερο κεφάλαιο περιγράφονται τα γενικά χαρακτηριστικά, δηλαδή ο τρόπος κατασκευής καθώς επίσης και ο τρόπος λειτουργίας των φραγμάτων Bragg. Αναφέρονται τα διάφορα είδη φραγμάτων Bragg που υπάρχουν και οι μηχανισμοί φωτοευαισθησίας τους. Στο τρίτο κεφάλαιο δίνεται έμφαση στη χρήση των φραγμάτων Bragg σαν αισθητήρες ταυτοποίησης της φύσης των υγρών στα οποία εισάγονται οι αισθητήρες αλλά και σαν αισθητήρες μέτρησης στάθμης υγρών. Τα φράγματα Bragg χρησιμοποιούνται ευρέως και σαν αισθητήρες πίεσης, θερμοκρασίας, ροής, μετατόπισης στάθμης υγρών, χημικής ταυτοποίησης, PH, ηλεκτρικών πεδίων, μαγνητικών πεδίων καθώς και άλλων φυσικών μεγεθών. Ακόμα γίνεται μια περιγραφή της διαδικασίας χημικής απογύμνωσης (etching), καθώς επίσης και τα τεχνικά χαρακτηριστικά και τρόπους λειτουργίας της πηγής φωτός που χρησιμοποιήθηκε, η οποία είναι ένας ενισχυτής Erbium Doped Fiber Amplifier –EDFA. Το τέταρτο κεφάλαιο πραγματεύεται τα αποτελέσματα των προσομοιώσεων που έγιναν με τη χρήση του προγράμματος COMSOL Multiphysics 4.2. Οι προσομοιώσεις έγιναν για διαφορετικές τιμές δεικτών διάθλασης μιας ποικιλίας υγρών. Στο πέμπτο κεφάλαιο αναλύεται το πειραματικό μέρος της ειδικής ερευνητικής εργασίας. Παρουσιάζονται η πειραματική διάταξη και τα πειραματικά δεδομένα που ελήφθησαν στο εργαστήριο Laser, καθώς επίσης και τα σχετικά σχόλια σύγκρισης με τα αποτελέσματα των αντίστοιχων προσομοιώσεων που έγιναν. / -

Orientador: Younès Messaddeq / Banca: Sandra Helena Pulcinelli / Banca: Oscar Peitl Filho / Banca: Gael Yves Poirier / Banca: Carlos Kenichi Suzuki / Resumo: A integridade das rotas ópticas depende da confiabilidade das fibras, que é afetada pelas condições de fabricação das fibras e cabos (matérias primas empregadas na fabricação do vidro e do revestimento e processo de fabricação) e pelas condições de operação da rota (ambiente da rota óptica e as tensões aplicadas durante o lançamento e vida útil). O objetivo deste trabalho é avaliar a degradação dos materiais que compõem as fibras ópticas e as consequências das variações de seus aspectos físico-químicos nas propriedades mecânicas e ópticas das fibras. Para tal foram realizados três tipos de envelhecimento nas amostras: 1 - envelhecimento hidrotérmico (em água deionizada a 85°C por 14, 28 e 49 dias) de amostras com revestimento acrilato e de carbono; 2 - envelhecimento em campo resultante em perda de confiabilidade mecânica e óptica; e 3 - envelhecimento por passagem de 500 mW, sob raio de curvatura de 10mm durante 30 minutos em de amostras com revestimento acrilato e de carbono. Observou-se que para o primeiro método de revestimento, as amostras revestidas têm resistência mecânica mais baixa que as amostras decapadas com H2SO4 a quente, possivelmente devido à mudança local de pH ou a atividade da água na superfície vítrea, dependendo do mecanismo de degradação do revestimento: cross link ou cisão de cadeias. No segundo método de envelhecimento, para as amostras com problemas de resistência mecânica, notou-se que o problema se encontrou na formulação dos revestimentos, faltando plastificante no revestimento primário e excedendo o mesmo material no revestimento secundário. Esse efeito tornou o polímero interno menos aderido ao vidro, e o externo menos capaz de suportar as tensões mecânicas normais de utilização da fibra óptica, tornando o guia de onda menos resistente mecanicamente. / Abstract: The integrity of optic network depends on the reliability of optical fibers, affected by cable and fibers manufacture conditions (materials and process) and by the environmental use conditions (tensions applied during installation and long term use). The objective of this work is to evaluate degradation of the materials and the consequences of its physical-chemical aspects variations in the mechanical and optic properties of fibers. So, three types of aging in the samples had been carried through: 1 - hydro-thermal aging (in deionized water at 85°C for 14, 28 and 49 days) of samples with acrilate and carbon coatings; 2 - field aging resulting in loss of mechanical and optical reliability; and 3 - aging by optical power of 500 mW, under 10 observed that for the first covering method, the coated samples had lower mechanical resistance than the uncoated samples (with hot H2SO4), due to local change of pH or changes of water activity in the glass surface, depending on the degradation mechanism of the coating material: cross link or chain scission. In the second aging method, for the samples with mechanical reliability problems, we noted the problem was in the formularization of coating, where it was missing plasticizer in the primary coating and exceed in the secondary coating. This effect became internal polymer not adhered enough to the glass, and external one incapable to support the normal mechanical tensions of use of an optic fiber, causing low mechanical reliability. For the samples with problems of optical attenuation, the cause of the problem was the wrong preparation of secondary coating, evidenced by its high Tg value. / Doutor

[pt] O objetivo principal deste trabalho foi o de estudar as redes de Bragg em fibras ópticas e suas principais aplicações, com especial interesse na compensação de dispersão de pulsos ópticos em sistemas de telecomunicações, onde uma implementação original foi construída. Faz-se uma revisão geral das técnicas existentes para fabricá-las e caracterizá-las, além de suas principais aplicações, não somente na área de telecomunicações mas também na área sensoriamento óptico. São mostrados os resultados experimentais obtidos nas montagem realizadas para escrever redes de Bragg em fibras ópticas e para caracterizá-las. Algumas experiências usando redes de Bragg para o controle do comprimento de onda de emissão de um laser de semicondutor e para medição de força aplicada numa estrutura são mostradas. São mostrados também os resultados experimentais inéditos obtidos com a compensação de dispersão de pulsos ópticos em enlaces de telecomunicações, onde várias montagens foram realizadas para comprovar a superioridade da utilização da redes de Bragg para esse fim. Demonstra-se também um sistema para gerar pulsos solitônicos sintonizável em comprimento de onde numa faixa de MHZ. Finalmente são mostrados os resultados obtidos com a utilização de fibras ópticas para chaveamento interferométrico de luz. Neste sistema são utilização como elemento óptico não linear fibras tipo D, com e sem redes de Bragg, revestidas com filme de materiais semicondutores amorfos. / [en] Bragg grating in optical fibers are used to compensate the dispersion of optical pulses in telecommunication systems. Initially, an overview is presented of the existing fabrication techniques of such gratings, as well as the techniques used for characterization. Some useful applecations in telecommunications and sensing are also shown. The results obtained in the set-up to write and to characterize Bragg gratings are presented. Some measurements were also done with typical applications such as controlling the emitting wavelength in semiconductors lasers, and monitoring the applied pressure in an optical fiber. Some new results are described on dispersion compensation in fibers. Using specially chirped Bragg gratings to pre- compensatedispersion of an optical pulse in a 80 km fiber link, we demonstrated that the poor quality of the input laser pulses has little impact on the duration of the pulses recovered after transmission. Finally, an interferometric switching arrangement using a semiconductor coated D fiber as nonlinear control element, is presented. The configuration uses infrared optical pulses to control a continuous wave light signal. It is also shown that the original reflected wavelength of a semiconductor coated D-fiber with Bragg grating can be shited with an external optical control signal.

Non-classical light sources are a fundamental building block of quantum photonic technologies. As these photonic technologies require higher numbers of sources and more specific source properties, it becomes increasingly important to characterize and manipulate these sources effectively. This thesis consists of three main projects, all relating to non-classical sources of light. First, we present a method for the rapid measurement of the joint spectral intensity of fiber-based photon pair sources. This method extends the concept of Stimulated Emission Tomography, using a chirped, broadband seed beam to stimulate the four wave mixing interaction. The use of the broadband seed, generated through supercontinuum generation, allows for measurements on the few second timescale and requires only a single pump laser to achieve high resolution joint spectra. In the second project, we use this characterization tool to test a variety of different fiber-based photon pair sources. We use three different modification approaches (bending, squeezing, and tapering) to induce changes in the joint spectral properties of the photon pair sources. We show that each of these modifications has some impact on the joint spectra measured. The resulting joint spectra are very complex, highlighting the importance of performing measurements rather than relying on calculations alone. Lastly, we demonstrate a fast switch for the manipulation of single photons. The switch uses the optical Kerr effect to rotate the polarization state of single photons at ultrafast timescales. The implementation of this switch is experimentally straightforward, using a commercial, single mode fiber as the Kerr medium and nJ level pump powers. We operate at an 80 MHz repetition rate and measure 97% switching efficiency, picosecond level switching speed, and approximately 800:1 signal to noise ratio from the operation.