Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: VI. Evolution in the degree of polarization of nonmonochromatic radiation traveling in a twisted optical waveguide

An analysis is made of the evolution of polarization of nonmonochromatic ra diation travelling through single-mode optical fibers in the presence of ra ndom coupling between orthogonally polarized modes, which is caused by the random twist of axes of natural linear birefringence of an SMF, and in the presence of a regular axis twist. It is shown that the depolarization lengt h of nonmonochromatic radiation in an SMF increases with increasing regular SMF twist, regardless of the presence of a random axis twist. Using the Mo nte Carlo method, the dependences of the mathematical expectation and the m ean-square deviation of the degree of polarization of nonmonochromatic radi ation on the fiber length for SMFs with different linear birefringences and regular axis twists are calculated. It is shown that the fiber length on w hich the degree of polarization of nonmonochromatic radiation reaches its l imiting value increases and the limiting value itself decreases with an inc reasing regular twist. It is also shown that an induced SMF twist is able t o improve parameters of a fiber interferometer, in particular, to decrease random phase changes and intensity fadings of the interference signal, whic h are caused by random coupling between polarization modes. (C) 2000 MAIK " Nauka/Interperiodica".