The Creation of Optical Transmitter Simulation for Indoor Free Space Optical Network Based on the Optical Fibers

Import 05/08/2014Cieľom tejto diplomovej práce je vytvorenie optického vysielača tvoreného zväzkom optických vláken pre vnútornú optickú bezvláknovú sieť, ktorý bude mať najrovnomernejšie rozloženie optického výkonu v priestore. Hlavným dôvodom vytvorenia tohoto optického vysielača je vytvorenie nového smeru v oblasti komunikácie v optických bezvláknových sieťach využívajúcich optické vlákno ako vysielač, pretože zatiaľ boli navrhnuté len vysielače, ktoré boli tvorené iba jedným optickým vláknom. Vysielač navrhnutý v tejto práci umožní väčšie pokrytie priestoru a dosiahnutie vyšších prenosových rýchlostí. Prvá časť práce je venovaná teoretickému úvodu do optických bezvláknových sietí, ich rozdeleniu a komunikácií v nich. Ďalej sú popísané komunikačné technológie, ktoré sa používajú vo vnútorných bezvláknových sieťach, konkrétne technológie VLC, MIMO a OFDM. V nasledujúcich častiach práce sú rozobraté optické komponenty, ktoré sa v danej sieti používajú ku komunikácií. Rozobraté sú šošovky, kolimátory a optické koncentrátory. Po tejto časti nasleduje časť, v ktorej sú popísané vysielače pre optickú bezvláknovú sieť, ktoré boli doteraz vytvorené. Hlavná časť tejto práce je venovaná vytváraniu simulácií už spomínaného optického vysielača s rôznym počtom optických vláken a analyzovaniu daných rozložení optického výkonu. Posledným krokom tejto práce je popis uskutočneného reálneho experimentálneho merania rozloženia optického výkonu v temnej miestnosti laboratória katedry Telekomunikačnej techniky.The goal of this diploma thesis is to create an optical transmitter which is composed from a bundle of optical fibers for indoor fiber-free optical network, which will have the most even distribution of optical power in space. The main reason for creating this optical transmitter is the creation of a new direction in the field of communication in optical fiber-free networks using optical fiber as a transmitter, because so far transmitters created by single optical fiber only have been designed. Transmitter designed in this thesis allows coverage of larger area and higher transmission speed. The first part of this thesis is devoted to theoretical introduction to optical fiber-free networks, their divisions and communications in them. Afterwards, communication technologies that are used in indoor free space optical network are described, especially the VLC, MIMO and OFDM technologies. In the following sections of thesis optical components that are used in the network for communication are discussed. Discussed are lenses, collimators and optical concentrators. This section is followed by a section where transmitters for optical fiber-free network that have been created till now are described. The main part of this thesis is devoted to creating simulations of the above-mentioned optical transmitter with a different number of optical fibers and the analysis of the distribution of optical power. The final step of this thesis is the description of the real experimental measurements of optical power distribution in a dark room laboratory of the department of Telecommunications.440 - Katedra telekomunikační technikyvýborn

On Micro Optical Elements for Efficient Light Diffusion

Efficient light management is one of the key issues in modern energy conversion systems, be it to collect optical power or to redistribute light generated by high power light emitters. This thesis touches mainly on the subject of efficient light redistribution for high power sources by means of refractive and reflective micro optical elements. Refractive micro optical elements have dimensions that are big enough to neglect diffraction phenomena and small enough to be still manufactured by the methods used in micro fabrication, typically above 50 micron for visible light but below or of the order of one millimeter. The advantage of this limitation that could be called the “refraction limit” is that the design and performance predictions can be based on simple methods such as ray tracing or the edge ray principles for non-imaging optics. In contrary to many studies on engineered diffusers we concentrate here on optical surface where the functional is given by concave shapes! The first part of the thesis treats the development and fabrication of one dimensional small angle diffusers for collimated high power and potentially coherent light sources. The generation of high power laser lines with a uniform intensity distribution is useful for the optimization of laser manufacturing applications such as annealing of amorphous silicon on large surfaces. This is typically needed for the fabrication of TFT’s or thin film solar cells. The one dimensional diffusers discussed in this thesis are based on an array of concave cylindrical microlenses with a typical lens width of 200 μm and a radius of curvature ranging from 300 μm to 1500 μm. In order to avoid diffraction grating effects due to the regular nature of the array a statistical variation of the lens width was introduced. The proposed fabrication process is based on isotropic etching of fused silica in hydrofluoric acid. The fabrication and design parameters were explored and their influence on the final performance determined. Extensive computer simulations based on ray tracing and diffractive beam propagation were compared with the measured performance of fabricated devices. Design rules based on an analytical model were also developed and verified. The performance under real world conditions were tested with good results for the smoothing of laser lines at the Bayrisches Laserzentrum in Erlangen, Germany. The subject of the second part are compact large angle transformers and their possible applications. A short introduction to non-imaging optics and its basic design tools are followed by development of the compound parabolic concentrator (CPC) based on work known for thermal solar concentration. This non-imaging light funnel is concentrating light and has the ability to efficiently transform the angle of an incoming bundle of rays into large angles up to the full half sphere. If inversed, the CPC works as a collimator. The novelty of the approach presented in this thesis lies in the reduced dimensions of the design and the use of the concentrator not as such but rather as an angle transformer with very high efficiency. When the dimensions of the classical solar concentrators are usually of the order of a few 10 cm or more the design developed in this thesis has dimensions of a few mm or less. Different possible applications for a compact CPC array are discussed such as LED collimation at chip level, fiber coupling with large numerical aperture and improved light management for thin film solar cells. The fabrication of a prototype of a compact dielectric filled CPC array as a proof of concept is described and first attempts at its characterization are discussed