I. P. Kovalyov - Ph.D. (Eng.), Associate Professor of Department of Theory of Circuits and Telecommunications, Nizhny Novgorod State Technical University n.a. R.E. Alekseev. E-mail: kovalyov@nntu.nnov.ru N. I. Kuzikova - Ph.D. (Eng.), Associate Professor of Department of Physics and Technology of Optical Communication, Nizhny Novgorod State Technical University n.a. R.E. Alekseev. E-mail: physics@nntu.nnov.ru