The article briefly describes the technical solution for the use of specialized fiber-optic cable embedded in ground wire (OPGW) on the sections of electric Railways AC. The technical solution is to combine in a single conductor functions return conductor and fiber optic communication lines. Are given the relevance of such decisions and some peculiarities of its implementation. The main part of the article examines to the selection options return conductor with combined functions. The article describes the theoretical dependencies for the combined selection of the conductor based on the thermal resistance criterion. As one of the main passport parameters of the OPGW cables is the section of the metal component, the percentage of their content and the variation percentages are used in calculations to determine the electrical resistance of the cable and the magnitude of the permissible current. This approach allows to determine the parameters of the cable based on the criterion of reliability and allows to obtain the cable composition for a subsequent order from the manufacturer. The algorithm of selection combined return conductor that contains two stages: pre-selection based on the reference data, the choice of the real parameters from the manufacturer.

Keywords: OPGW, reverse wire, combined reverse wire, electrothermal degradation, fiber-optic transmission lines railway transport, traction network, the choice of combined shield wire

The ability to change brightness contrast of images with the help of some graphic packages’ tool is studied. In parallel the influence of this tool on hue and saturation of forming the image pixels is investigated. It is shown that tool as a whole is of little use for brightness contrast informative control, because in a number of packages it cannot provide brightness contrast gain, in others - does not keep hue and in all - deforms a saturation that threatens with loss of the graphic information transferred by saturation contrasts. Corresponding artifacts are considered and discussed.

Keywords: nonlinear brightness control, brightness contrast, colour hue and saturation, graphic information integrity, artifacts

In the article managed photon pairs generation methods in lightguides with actively formed dispersion for producing a single-photon light state are discussed. Generation principle is based on of spontaneous parametric scattering or spontaneous fourwave mixing. To get the factored state, i.e. spectral and spatial correlations between daughter photons are eliminated, the usage of photonic crystal fiber, that allow to form complex frequency dispersion profiles by changing the fiber structure, is analyzed.

Keywords: photonic-crystal fiber, quantum communications, femtosecond laser, actively formed dispersion, photon pairs, single-photon states

Modern sources based on the usage of spontaneous four-wave mixing in photonic-crystal fibers generate photon pairs in wide wavelength range. Microstructured fibers allow actively managing frequency dispersion profile. In the design of different types of photonic-crystal fibers is necessary to research the influence of microstructure on fibers properties. Nowadays one of the most perspective solutions is numerical and program modeling. Paper presents modeling of photonic-crystal fiber structures to find optimal parameters of the nonlinear medium.

Keywords: photonic-crystal fiber, modeling, photon pairs, single-photon states, spontaneous four-wave mixing