A luz, desde os primórdios da civilização, vem sendo utilizada com finalidades terapêuticas. O uso da helioterapia foi amplamente baseado em crenças religiosas e superstições. Os homens pré-históricos endeusaram o sol e consequentemente a luz solar, os quais foram considerados sagrados, sendo a eles atribuída a capacidade de afastar maus espíritos capazes de provocar doenças. Os deuses solares da Antiguidade eram considerados deuses da saúde e da cura.Devido à baixa qualidade dos relatos referentes ao emprego da helioterapia, sua eficácia é de difícil julgamento. Contudo, dados vindos das literaturas grega e romana mencionam que essa modalidade terapêutica foi utilizada largamente no tratamento da epilepsia, artrite, asma e obesidade. Nessas culturas, o banho de sol era tido como uma atividade saudável e um método de medicina preventiva, como reconhecido por Heródoto no século VI a.C.Simultaneamente à adoração das várias formas de agentes emissores de luz, esta foi utilizada pelos seres humanos de forma terapêutica e científica.
We investigate the transmission performance of an optical signal composed by a custom orthogonal frequencydivision multiplexing (OFDM) gigabit ethernet (GbE) signal, a long-term evolution (LTE) signal, and an OFDM ultrawideband (OFDM-UWB) signal, when chirp is introduced in the intensity modulation based on a dual electrode Mach-Zehnder modulator. The results show that, when the optical signal is generated with controlled negative chirp, it is possible to reduce the optical signal-to-noise (OSNR) penalty after transmission through a long reach fiber-to-thehome network by approximately 5, 1.5, and 0.5 dB, for the OFDM-UWB, LTE, and OFDM-GbE signals, respectively. Furthermore, the results show negative OSNR penalty for OFDM-UWB and LTE signals after transmission, for specific distances.Index Terms-Chirp, dispersion compensation, dual electrode Mach-Zehnder modulators (DEMZM), hybrid long reach fiber-to-the-home networks.
Abstract-In the literature, two system solutions have been proposed to overcome high dispersion problems typical of G.652 fibers at high bit rates (40 Gb/s): they are periodic and all-at-the-end dispersion compensation. We carry out an exhaustive comparison between the two methods that, up to this moment, have been studied separately. In the first part, we introduce a simplified model on strong dispersion management (DM) with intrachannel four-waves mixing (IFWM) and intrachannel cross-phase modulation (IXPM). We then carry out extensive numerical simulations of a complete system in order to verify the results as a function of the input average power and of the input pulsewidth. Finally, we tackle a typical system aspect, i.e., the influence of nonlinear effects on dispersion compensating fibers (DCFs).
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