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Aquest document presenta una visió global del procés de desenvolupament de la pàgina web "rankitt.com", una web social per a enquestes. L'autor d'aquestes línees exposa els fonaments teòrics en els que es recolça el projecte i realitza l'anàlisi i disseny general de l'aplicació. En este documento se presenta una visión global del proceso de desarrollo de la página web "rankitt.com", una web social para encuestas. El autor de estas líneas expone los fundamentos teóricos en los que se apoya el proyecto y realiza el análisis y diseño general de la aplicación. This document is an overall view about the development process of a 3D Virtual Community of Learners prototype called "Shere Rom Space" (SRS). The author explains project's theoretical main concepts and makes the application general analysis and design. Nota: Aquest document conté originàriament altre material i/o programari només consultable a la Biblioteca de Ciència i Tecnologia.

The influence of Bragg fiber design parameters on photonic bandgap was discussed via the finite element method.The theoretical results show that the bandgap move to long wavelength when the thickness or the refractive index of the Ge-doped layers increases.A novel W-shape-core Bragg fiber was firstly proposed by introducing a F-doped low index layer adjacent of fiber core.The calculation demonstrates the W-shape-core Bragg fiber can reduce the confinement loss and improve the bending-resistant ability effectively.A W-shape-core Bragg fiber was designed with a core diameter of 30 μm,which has a loss of 0.1 dB/km at wavelength of 1.06 μm and is proved single mode propagation theoretically.

A two-stage all-fiber single-frequency MOPA is demonstrated. It provides 80W output power with a slope efficiency of 70% at 1064 nm. The phase noise of the fiber amplifiers measured by using multi-dithering technique is less than 50Hz.

Aquest document presenta una visió global del procés de desenvolupament de la pàgina web "rankitt.com", una web social per a enquestes. L'autor d'aquestes línees exposa els fonaments teòrics en els que es recolça el projecte i realitza l'anàlisi i disseny general de l'aplicació. En este documento se presenta una visión global del proceso de desarrollo de la página web "rankitt.com", una web social para encuestas. El autor de estas líneas expone los fundamentos teóricos en los que se apoya el proyecto y realiza el análisis y diseño general de la aplicación. This document is an overall view about the development process of a 3D Virtual Community of Learners prototype called “Shere Rom Space” (SRS). The author explains project’s theoretical main concepts and makes the application general analysis and design. Nota: Aquest document conté originàriament altre material i/o programari només consultable a la Biblioteca de Ciència i Tecnologia.

The horizontal propagation characteristics of supercontinuum source in non-Kolmogorov turbulence is investigated.A superposition of narrow-band spectral components is used to simulate supercontinuum.The beam width of supercontinuum source and propagation efficiency are calculated with different inner and outer scales of turbulence and parametersα,as well as with various turbulence levels and different beam qualities for the spectral parts of supercontinuum source.The method of cross-spectral density is introduced here,and the atmospheric extinction is considered.It is shown that the change of parameterα,the outer scale and inner scale of turbulence, bring about different numerical results.It is also shown that turbulence can influence the beam width and induce deterioration of propagation efficiency,especially for the situation that all the spectral parts of supercontinuum source are Gaussian fundamental modes.When the spectral parts are higher-order modes,the factor affecting propagation of supercontinuum source dominantly is diffraction.

Broadband normal dispersion pumping supercontinuum (SC) generation in silica photonic crystal fiber (PCF) is investigated in this paper. A 1064-nm picosecond fiber laser is used to pump silica PCF for the SC generation. The length of PCF is optimized for the most efficient stimulated Raman scattering process in the picosecond pump pulse region. The first stimulated Raman Stokes peak is located in the anomalous dispersion regime of the PCF and near the zero dispersion wavelength; thus the SC generation process can benefit from both a normal dispersion pumping scheme and an anomalous dispersion pumping scheme. The 51.7-W SC spanning from about 700 nm to beyond 1700 nm is generated with an all-fiber configuration, and the pump-to-SC conversion efficiency is up to 90%. In order to avoid the output fiber end face damage and increase the stability of the system, an improved output solution for the high power SC is proposed in our experiment. This high-efficiency near-infrared SC source is very suitable for applications in which average output power and spectral power density are firstly desirable.

A novel fiber Bragg grating thermal tuning scheme is proposed, theoretically analyzed and experimentally studied. The device made from this scheme is named doubleshoulder beam (DSB). Experimental results demonstrate that DSB is an effective thermal tuning technique. A thermal sensitivity of 0436?nm/℃, 50 times that of the bare fiber grating, is experimentally achieved. To our knowledge, this is the largest thermal sensitivity ever demonstrated. The repeatability and lin earity of the technique is very well. The most important advantage of DSB, as a breakthrough to conventional thermal tuning technique, is its great flexibility. It makes the thermaltuning efficiency of fiber grating no longer limited by the thermalexpansion coefficient of the drive materials, but can be designed according to practical requirements. This technique is expected to have a vast application in fields such as laser tuning, high sensitivity temperature sensing, sensor demultiplexing and so forth.