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The influence of multiray interference on a propagation pulsed signal in fiber-optic communication line (FOCL) is considered. The multiray interference appears for each place, where the defect on optical factor of refraction occurs. The problem of distortion pulsed signal becomes particularly actual with development high speed calculate optical networks, which have a high degree an structure, and appearance of transmit technology of information with a spectral compaction. This is explained increasing amount of components in a transmit tract. Such optical processes are like the processes, appearing in multiray Fabry-Perot interferometer (FPI). In approach to a propagation light wave is close to flat, the model of a segment FOCL is built on the base of an independent FPI elements composition. Such model has allowed to make the quantitative estimation of interference multiplicated hindrance parameters by means statistical description of many elements FPI in FOCL system. The studies have shown, that for reflect index from butt-end of fiber within 3...5% the typical peaks of intensity during increasing of a signal pulse front are appeared. This case the count threshold in a decisive device for pulse with garbled fronts is reached in other moment of time to not-garbled fronts. The time delay result in a phase delay between consequences of pulses, which increase the probability of reading errors the bits. For active components FOCL situation is danger, when all or part of interferometers leave maximum their own transmission and the reflected wave will appear. The estimation of its amplitude is carried out, the correlation function and the spectrum of many elements FPI in FOCL hindrances are putted.
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