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Alexeyev C.N.,Taurida National University | Boklag N.A.,National Space Facilities Control and Test Center | Yavorsky M.A.,Taurida National University
Journal of Optics | Year: 2010

The structure of hybrid higher order modes of two coupled weakly guiding identical optical fibres is studied. On the basis of perturbation theory with degeneracy for the vector wave equation expressions for modes with azimuthal angular number ℓ ≥ 1 are obtained that allow for the spin-orbit interaction. The spectra of polarization corrections to the scalar propagation constants are calculated in a wide range of distances between the fibres. The limiting cases of widely and closely spaced fibres are studied. The obtained results can be used for studying the tunnelling of optical vortices in directional couplers and in matters concerned with information security. © 2010 IOP Publishing Ltd.


Alexeyev C.N.,Taurida National University | Boklag N.A.,National Space Facilities Control and Test Center | Fadeyeva T.A.,Taurida National University | Yavorsky M.A.,Taurida National University
Journal of Optics | Year: 2011

We study the evolution of circularly polarized optical vortices (OVs) in the system of two coupled few-mode optical fibres. We demonstrate that upon propagation OVs tunnel into the adjacent fibre as a complex superposition of OVs that comprise also OVs of opposite polarization and topological charge. The initial OV may tunnel into the other fibre as the same vortex state of lesser energy. The evolution of the orbital angular momentum in coupled fibres is studied. © 2011 IOP Publishing Ltd.


Nechaeva M.,Ventspils International Radio Astronomy Center | Antipenko A.,Radiophysical Research Institute RRI | Bezrukovs V.,Ventspils International Radio Astronomy Center | Bezrukov D.,Ventspils International Radio Astronomy Center | And 17 more authors.
Baltic Astronomy | Year: 2013

An experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (R.T-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.


Nechaeva M.B.,Radiophysical Research Institute | Dugin N.A.,Radiophysical Research Institute | Antipenko A.A.,Radiophysical Research Institute | Voytyuk V.V.,National Space Facilities Control and Test Center | And 12 more authors.
Radiophysics and Quantum Electronics | Year: 2015

An experiment on VLBI radar of the 2012 DA14 asteroid was carried out on February 15–16, 2011 at the time of its closest approach to the Earth. The research teams of Kharkov (Institute of Radio Astronomy of the National Academy of Sciences of Ukraine), Evpatoria (National Space Facilities Control and Test Center), Nizhny Novgorod (Radiophysical Research Institute), Bologna (Istituto di Radioastronomia (INAF)), and Ventspils (Ventspils International Radioastronomy Center) took part in the experiment. The asteroid was irradiated by the RT-70 planetary radar (Evpatoria) at a frequency of 5 GHz. The reflected signal was received using two 32-m radio telescopes in Medicina (Italy) and Irbene (Latvia) in radiointerferometric mode. The Doppler frequency shifts in bi-static radar mode and interference frequency in VLBI mode were measured. Accuracy of the VLBI radar method for determining the radial and angular velocities of the asteroid were estimated. © 2015, Springer Science+Business Media New York.

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