Optical Amplifiers for Access and Passive Optical Networks: A Tutorial

For many years, passive optical networks (PONs) have received a considerable amount of attention regarding their potential for providing broadband connectivity, especially in remote areas, to enable better life conditions for all citizens. However, it is essential to augment PONs with new features to provide high-quality connectivity without any transmission errors. For these reasons, PONs should exploit technologies for multigigabit transmission speeds and distances of tens of kilometers, which are costly features previously reserved for long-haul backbone networks only. An outline of possible optical amplification methods (2R) and electro/optical methods (3R) is provided with respect to specific conditions of deployment of PONs. We suggest that PONs can withstand such new requirements and utilize new backbone optical technologies without major flaws, such as the associated high cost of optical amplifiers. This article provides a detailed principle explanation of 3R methods (reamplification, reshaping, and retiming) to reach the extension of passive optical networks. The second part of the article focuses on optical amplifiers, their advantages and disadvantages, deployment, and principles. We suggest that PONs can satisfy such new requirements and utilize new backbone optical technologies without major flaws, such as the associated high cost

Software-Defined Optics in Last Mile for Research and Education in the Czech Republic

The Software Defined Networking (SDN) gained recognition due to its improvements at the packet switching and routing layers. The benefits of programmable, remotely controllable networking devices can be applied to the optical layer of contemporary networks as well. This work introduces CESNET's Czech Light~® family of devices and their role in enabling the SDN approach within the CESNET's production network. As a case study, an upgrade of the Cheb node in CESNET's network from a hard-spliced add-drop multiplexers to SDN-capable Reconfigurable Optical Add-Drop Multiplexers (ROADM) is presented. The upgrade improved operational capabilities of the network, including remote channel equalization, and the possibility to deploy new channels or lambdas without physical intervention. The deployment of ROADM also improved the optical properties of the network

Simulation of Low Frequency Electromagnetic Field Effect on Cell Membrane Channels Model

According to many current investigations, which approve the direct impact of potassium or sodium channels to the cell dividing processes, the presented article outlines an attempt to simulate influence of low frequency electromagnetic field to the cell membrane channels. Activation or inhibition of ion channels could be achieved by various mechanisms e.g. most common is chemical way. In contrast with this fact, the article describes simulations of external low frequency electromagnetic field application on the cell model, which should provide results comparable to the conventional methods

New Approach to Metal Biomarker Detection Using Nonionizing Electromagnetic Field

Medical detection techniques used for preoperative scanning of certain marked areas are mostly based on ionizing radiation as it is in case of CT. This paper provides an unusual approach to detection of metal biomarkers implanted into the human body, based on nonionizing radiation and discusses problems and complications connected with chosen technique

Diagnostika homogenity rozlozeni rekombinacnich center ve strukturach Si solarnich clanku metodou LBIV.

The thesis deals with characterization of solar cells (SC) by local irradiation of surface. It is important for improving and making more effective production of SC. The 1st part describes theory and physics important for describing a photovoltaic phenomena. Theory of PN junction, optical generation and all mechanisms for recombination are espetially mentioned. Methods used for measuring and characterization of SC are described in the 2nd part. The described measuring method allows a simplification and speed up of the in-process diagnostics of SC. The distribution of the measured UOC induced by local infrared irradiation mostly corresponds to the local defect distribution in the single-crystalline material of the P-base, that may be also influenced by high-temperature processes. The experiments are described in the last part. A new method for measurement of SC, called LBIV (light beam induced voltage), was developed. On the base of our experiments, 3 basic groups of monocrystalline Si SC were discovered. There is strong correlation between distribution of measured UOC and efficiency of SC. The results of numerical simulations conform with measured distribution UOC for all three groups of SC. Some experiments were done for polycrystalline Si SC. In this case, no consistent results were found for distribution UOC and efficiency. The new LBIV method can be used as fast in-process checking and investigating the influence of technology on homogeneity of SC and consequently to help to increase efficiency and reliability of SC. Additionally the thesis outlines areas of possible further research activities with LBIV method.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Transmission delay stabilization using commercial pluggable small form factor transceiver based on V-cavity laser

In this paper, we introduce and verify direct wavelength tuning of V-cavity laser based transceiver as a method for optical stabilization of the end-to-end delay of an optical fiber link. Other mostly deployed methods of optical stabilization are briefly overviewed together with particular lasers available in commercial transceivers. Fine tuning procedure for chosen V-cavity laser based transceiver is proposed, and such process is verified, increasing finesse at least 13 times (40 times on selected intervals).</p