Fiber waveguides with stable polarization of radiation

It is suggested that the mode polarization may be conserved by employing three-layer rectangular and elliptic fiber waveguides in which the outer cladding is made of a material with high dielectric losses or of a dielectric with a refractive index higher than that of the inner cladding. An analysis is made of the influence of the difference between the phase and attenuation constants on the mode polarization stability. It is shown that there are optimal waveguide parameters for which the coupling between orthogonally polarized modes is minimal.