A.P. Kamantsev - Junior Research Scientist, Kotelnikov IRE RAS (Moscow) E-mail: kama@cplire.ru A.V. Mashirov - Research Scientist, Kotelnikov IRE RAS (Moscow) V.V. Koledov - Dr.Sc. (Phys.-Math.), Leading Research Scientist, Kotelnikov IRE RAS (Moscow) L.N. Butvina - Ph.D. (Phys.-Math.), Senior Research Scientist, Fiber Optics Research Center of RAS