This masters thesis is focusing on the issue of passive optic access networks. It is dealing with the limiting factors for broadband connections, especially attenuation of fibre optics and dispersion. It is also dealing with most commonly used standards of passive optic networks. It clarifies the issue of wavelength-division multiplexing, its advantages and disadvantages, used standards, various types of components for the WDM-networks, their characteristics, application etc. In the practical part of the work you can find the measuring and diagnostics of the passive optic network EPON. It contains measuring by the direct method OLTS, measuring by the Pon Power Meter and optic reflectometer OTDR. At the end I am dealing with the measuring of splitter in the rate of 1:16.

This project focuses on wavelength division multiplexing passive optical network (WDM-PON) supervision using optical time domain reflectometer (OTDR) for detection and localization of any fault occurred in optical distribution network. The objective is to investigate the impact of OTDR monitoring signal on the data transmission in the WDM-PON based on wavelength re-use system, where the same wavelength is assigned for both upstream and downstream to each end user. Experimental validation has been carried out to measure three different schemes, i.e. back-to-back, WDM-PON with and without OTDR connection by using 1xN and NxN arrayed waveguide gratings. Furthermore, a comprehensive comparison has been made to trace out the effect of the monitoring signal which is transmitted together with the data through the implemented setup. Finally, the result has confirmed that the OTDR supervision signal does not affect the data transmission. The experiment has been carried out at Ericsson AB, Kista.

A distributed sensor using an optical fiber for detecting and locating intruders over long perimeters (>10 km) is described. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (φ−OTDR). Light pulses from a cw laser operating in a single longitudinal mode and with low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. In laboratory tests with 12 km of fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on φ−OTDR traces were characterized. In field tests in which the sensing element is a single mode fiber in a 3-mm diameter cable buried in an 8 to 18 inch deep, 4 inch wide trench in clay soil, detection of intruders on foot up to 15 ft from the cable line was achieved. In desert terrain field tests in which the sensing fiber is in a 4.5-mm diameter cable buried in a 1 ft deep, 2.5 ft wide trench filled with loose sand, high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km in real time. In a final series of field tests in clay soil, phase changes produced by the steps of a person walking up to 15 ft away from the buried cable were observed, and vehicles traveling at 10 mph were consistently detected up to 300 ft away. Based on these results, this technology may be regarded as a candidate for providing low-cost perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.

A distributed sensor using an optical fiber for detecting and locating intruders over long perimeters (>10 km) is described. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (φ−OTDR). Light pulses from a cw laser operating in a single longitudinal mode and with low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. In laboratory tests with 12 km of fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on φ−OTDR traces were characterized. In field tests in which the sensing element is a single mode fiber in a 3-mm diameter cable buried in an 8 to 18 inch deep, 4 inch wide trench in clay soil, detection of intruders on foot up to 15 ft from the cable line was achieved. In desert terrain field tests in which the sensing fiber is in a 4.5-mm diameter cable buried in a 1 ft deep, 2.5 ft wide trench filled with loose sand, high sensitivity and consistent detection of intruders on foot and of vehicles traveling down a road near the cable line was realized over a cable length of 8.5 km and a total fiber path of 19 km in real time. In a final series of field tests in clay soil, phase changes produced by the steps of a person walking up to 15 ft away from the buried cable were observed, and vehicles traveling at 10 mph were consistently detected up to 300 ft away. Based on these results, this technology may be regarded as a candidate for providing low-cost perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.

The dissertation investigates the optical time domain reflectometer (OTDR) systems. The main object of research is an optical receiver for OTDR. The aim of the work is to create an optical receiver design method-ology to achieve optimal dynamic range of the system for a given band-width, design and investigate integrated fully differential variable gain tran-simpedance amplifier for OTDR optical receiver. Main tasks solved in this work are: perform analysis of OTDR struc-tures, main specifications and suggest possible improvement approaches; analyze main optical receiver noise sources and noise minimization and create generalized noise model; create optical receiver for an OTDR design methodology, that allow calculating avalanche photodiode multiplication factor, transimpedance amplifier feedback resistance and voltage amplifier input transistor dimensions that achieves optimal OTDR dynamic range; design and perform simulations of transimpedance amplifier integrated cir-cuit using AMS 0.35 µm CMOS technology and calculate optical receiver parameters in 0.1–100 MHz range of bandwidths The dissertation consists of four parts including Introduction, 4 chap-ters, Conclusions, References and 1 Annex. The introduction reveals the investigated problem, importance of the thesis and the object of research. It also describes the purpose and tasks, research methodology, scientific novelty, the practical significance of re-sults examined in the paper and defended statements. The... [to full text] / Disertacijoje nagrinėjamos laiko srities optinės reflektometrinės (OTDR) sistemos. Pagrindinis tyrimo objektas yra OTDR įėjimo pakopa – optinis imtuvas (OI). Disertacijos tikslas – sukurti OI projektavimo metodiką, lei-džiančią pasiekti optimalų dinaminį diapazoną, suprojektuoti ir ištirti integ-rinį diferencinį pereinamos varžos stiprintuvą (PVS) su kintamu stiprinimo koeficientu. Darbe sprendžiami šie uždaviniai: atliekama OTDR ir jų pagrindinių charakteristikų analizė ir formuluojamos tobulinimo kryptys; analizuojami pagrindiniai optinio imtuvo triukšmų šaltiniai, jų mažinimo galimybės ir su-daromas apibendrintas optinio imtuvo triukšmų modelis; sukuriama OI pro-jektavimo metodika, leidžianti apskaičiuoti griūtinio fotodiodo dauginimo faktorių, pereinamosios varžos stiprintuvo grįžtamojo ryšio varžą ir įėjimo tranzistoriaus fizinius matmenis, kuriems esant gaunamas optimalus dina-minis diapazonas; projektuojamas optinio imtuvo maketas iš diskrečiųjų elementų ir tiriami jo parametrai; atliekamas integrinio PVS projektavimas ir modeliavimas, taikant 0,35 µm KMOP technologiją bei optinio imtuvo pa-rametrų skaičiavimas 0,1–100 MHz dažnių juostų diapazone. Disertaciją sudaro įvadas ir keturi skyriai. Pabaigoje pateikiami naudo-tos literatūros ir autoriaus publikacijų disertacijos tema sąrašai ir 1 priedas. Įvadiniame skyriuje aptariama: tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, suformuluotas darbo tikslas bei uždaviniai, ap-rašoma tyrimų metodika... [toliau žr. visą tekstą]

[pt] Com a crescente demanda por maior capacidade na transmissão de dados, uma solução tem sido estudada para transmissão de rádio sobre fibra combinando múltiplos canais de dados sobre a portadora óptica na rede de acesso baseada em multiplexação por sub-portadoras. Ademais, essa rede de acesso é comumente ramificada na forma de uma rede óptica passiva. Monitoramento desses enlaces em fibra é, então, cada vez mais importante. A tecnologia atual de reflectometria óptica no domínio do tempo utilizada para monitoramento opera em um comprimento de onda óptico separado e possui ampla largura de banda de detecção, tornando-se relativamente cara. A busca por uma alternativa de monitoramento de alta precisão e baixo custo é de suma importância para a oferta de transmissão com garantia de qualidade de serviço. Neste trabalho, o uso de multiplexação por sub-portadoras é explorado, incorporando uma técnica de monitoramento de varredura de tom de baixa frequência na transmissão de dados. Um modelo matemático para a resposta em frequência do enlace foi derivado e a localização e a intensidade de uma falha são estimadas através da comparação com a amplitude e a fase detectadas da luz retroespalhadaa medida em que é feita uma varredura de frequência do sinal de monitoramento, aplicando-se um algoritmo de minimos quadrados. O modelo proposto considera que a medida do enlace antes da ocorrência de uma falha é conhecida. Uma única falha nova pode então ser detectada com precisão e sua posição e intensidade são estimadas da maneira descrita. / [en] With ever growing demand for higher capacity in data transmission, a solution has been proposed for analog Radio over Fiber transmission, combining several data channels over the optical carrier in the access network using Sub-Carrier Multiplexing (SCM). Furthermore, this access network is often branched in the form of a passive optical network (PON). Monitoring such fiber links is thus increasingly important. Current optical time domain reflectometry (OTDR) technology used for monitoring operates at a separate optical wavelength and has wide bandwidth detection, making it relatively costly. The pursuit of a low cost, high precision monitoring alternative is of paramount importance for cost effective quality of service (QoS) improvement. In this work employment of SCM for data multiplexing is exploited embedding a low frequency tone sweep monitoring technique into data transmission. A mathematical model for the frequency response of the link was derived and the fault location and intensity is estimated through comparison with acquired amplitude and phase of the backscattered light for the varying frequency by applying a simple least mean squared (LMS) algorithm. The modeling suggested requires that measurement of the link prior to the occurrence of a fault is known. A single new fault can then be accurately detected and its position and intensity estimated in the way described.