A novel coupler measurement station and technique for manufacturing fused biconical tapered multi-port multimode couplers with improved uniformity among ports is presented. Improvement in the uniformity of the couplers is achieved by diffusion of the minimum taper region of the coupler. The phenomenon of dopant transport from the core to the cladding (or from the cladding to the core) at high temperatures is known as diffusion. Diffusion of a germanium-doped core results in the germanium dopants migrating from the core into the cladding thus increasing the effective diameter of the core which is accompanied by a decrease in the refractive index. The cores of individual fibers in the minimum taper region are a few micrometers apart. Diffusion thus results in a minimum taper region that has approximately uniform refractive index leading to better uniformity among ports. The experimental setup and results of diffusion tests on multimode fiber with different core/cladding ratios are presented. A coupler station that is capable of making bi- directional measurements of the coupler is demonstrated successfully. The coupler station also enables a user to dynamically monitor the ports of the coupler during manufacture, and can be adapted to manufacture star couplers ranging in size from two to sixteen fibers. / Master of Science

Fiber optic sensors fabricated from standard silica fibers have many advantages over conventional sensors like small size, portability, durability and immunity to electromagnetic fields. Unfortunately, these sensors are not suitable for use in harsh environments where the temperatures are greater than 700°C and large working stresses are involved. Sapphire fiber-based sensors present an attractive alternative for use in such environments. The material properties of sapphire like high melting point, extreme hardness and relative imperviousness to chemical reactions, coupled with the advantages of optical fiber sensing, enhance the performance of these sensors for rugged use. Unfortunately, commercial sapphire fiber that is currently available has higher optical attenuation than silica fiber and is costlier. 0, it is prudent to use a small length of sapphire fiber as a sensor head, which is then spliced to a standard singlen10de silica fiber which acts a lead-in/lead-out fiber to the sapphire sensor head. This thesis investigates possible splicing techniques to fabricate such a sensor set-up. Comparative results from experiments performed on splices that have been obtained by each of these techniques, are presented. Furthermore, two different sensor configurations using a sapphire fiber, spliced to a silica fiber, are developed, and the results of preliminary tests are presented. / Master of Science

This thesis evaluates a new approach for effectively increasing the dynamic range of optical fiber links for transporting RF signals. This new approach, called the Dynamic Range Enhancement Technique (DRET), is key to connecting remotely located microcell base station antenna sites to a centralized base station via optical fiber while maintaining a good dynamic range. This thesis examines the causes and characteristics of distortion introduced by the optical fiber link and describes and compares the performance of the DRET with other dynamic range enhancing techniques using computer simulation. In most instances, the DRET is shown to be superior both in reducing harmonic and intermodulation distortion compared to other dynamic range enhancement techniques. The DRET has several advantages over automatic gain control (AGC) including stability and the absence of parasitic modulation on weak signals caused by fading or transient high power signals. / Master of Science

Orientador: Luiz Carlos Barbosa / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-04T20:34:50Z (GMT). No. of bitstreams: 1 GarciaRivera_VictorAnthony_M.pdf: 15268986 bytes, checksum: 03f47604e1a522457d30d9fa547a024d (MD5) Previous issue date: 2005 / Resumo: Neste trabalho de pesquisa, reporto a fabricação e caracterização de vidros germano-telurito para amplificadores ópticos curtos. Estes são fabricados em guias de onda planar e canal pela técnica de troca iônica e fibra em vidro, dopados com altas concentrações de íons de Er3+ cuja composição é: 75TeO2 ¿ 2GeO2 ¿ (10+x)Na2O ¿ (12-x)ZnO ¿ 1Er2O3 (mol%, onde x=0, 2 e 5). São preparados guias multímodos e monomodos, as profundidades dos guias podem ser controladas pela variação do tempo e da temperatura no processo da troca iônica. Com o vidro de maior índice de refração consegui fabricar fibra óptica (só nucleo) e solda com outro vidro de menor índice de refração, pela técnica de fibra em vidro. A preparação dos vidros foi feita pela técnica convencional de fusão à temperatura de 7500C. Encontrou-se grande estabilidade térmica nos sistemas vítreos. Realizou-se as medidas de espectroscopia Raman, absorção, emissão e tempo de vida, onde se mostra a maior largura de banda de emissão dos vidros germano-teluritos dopados com íons Er3+ quando comparado com amplificadores comerciais feitos à base de vidros silicatos. Os vidros já polidos passaram pelo processo de fotolitografía, durante a fabricação dos guias de ondas se empregou a técnica de troca iônica dos íons Ag+. Na+, processo tomando por base a temperatura de início de cristalização Tg; neste processo os vidros foram submergidos num banho de sais que continha 2AgNaO3 ¿ 49NaNO3 ¿ 49KNO3. Os índices efetivos dos modos foram medidos pela técnica de acoplamento por prisma com o equipamento Metricom. Foram determinados o perfil do índice de refração e os parâmetros da difusão: coeficiente de difusão efetiva De e a energia de ativação ED. Conseguiu-se fabricar guias de onda planar e canais monomodos e multímodos pela técnica de troca iônica em vidros germano-teluritos dopados com altas concentrações de íons de Er3+. Empregando a técnica de fibra em vidro, consegui fabricar um guia de onda. Método totalemente novo que consiste na solda de uma fibra óptica (núcleo) com um substrato de menor índice de refração que é a casca para esta fibra mediante esta técnica. Neste processo deve-se ter em conta a região de temperatura Tg ¿ Tx, para evitar possiveis processos de cristalização no processo de solda da fibra óptica com o substrato / Abstract: In this work the production and characterization of germane-tellurite glasses for small optical amplifiers are reported. These materials were applied in the manufacture of planar e channel waveguide using the technique of ionic exchange in glasses and fiber on glass, doped with high concentrations of ions of Er3+ whose composition is: 75TeO2 ¿ 2GeO2 ¿ (10+x)Na2O - (12-x)ZnO ¿ 1Er2 O3 (mol%, x= 0, 2 e 5). Multimode and monomode guides have been prepared, and the depths of the guide can be controlled for the time and the temperature variation in the process of the ionic exchange. With the glass of high refraction index, manufacture of the optic fiber (only nucleus), and welding this with another glass of smaller refraction index were carried out for the fiber technique on glass purpose. The preparation of glasses was made by the conventional technique of fusing at the temperature of 7500C and glasses of great thermal stability were obtained characterization Raman, optical absorption, light emission and lifetime measurements were performed. The optical absorption of glasses doped tellurite with ions Er3+ has been considerably broader than those of the amplifiers of glass base silicate glasses. The polishing of glasses was done using the photo-lithographical process during the construction of the waveguides. The technique of Ag+. Na+ ion-exchange was applied near Tg and below Tx. In this process, the glasses have been submerged in a bath of melted 2AgNaO3 ¿ 49NaNO3 ¿ 49KNO3. The effective refraction index was measured by the coupled prism technique using the Metricom equipment. The refraction index profile and the diffusion parameters as the diffusion effective coefficient De and the energy of activation ED were determined. Planar monomode and multimode waveguide channel was manufactured using the ion-exchange technique in germane-tellurite glasses doped with high concentration of Er3+ ions. A new method of glass fiber preparation is introduced and consists of the soldering of a fiber optic (nucleus) to a substrate of smaller refraction index. In this process the temperature region between Tg and Tx was avoided in order to prevent against any possible crystallization soldering process / Mestrado / Física / Mestre em Física