Depolarization of light in optical fibers

The evolution of radiation polarization in a non-uniform medium with a gradient refractive index profile using the quantum mechanical method of coherent states is investigated. It is shown that the degree of polarization of both linearly and circularly polarized radiation decreases with distance due to the interaction between polarization (spin) and trajectory (orbital angular momentum). The effect of asymmetry for the right- and left- circularly polarized radiation takes place in relation to the sign of helicity of the trajectories of sagittal rays. The wave nature of depolarization is emphasized. Depolarization disappears when the wavelength tends to zero lambda -> 0. Depolarization increases with an increase in the axial displacement of the beam, the gradient parameter of the waveguide and the wavelength of the radiation. The oscillations of the polarization degree of pure diffraction origin in the propagation of radiation in a single-mode optical waveguide are found. It is shown that the increase in the angle of rotation of the polarization plane with the distance is irregular and depends on the axial displacement or the angle of inclination of the beam to the waveguide axis. The fluctuations of Berry's phase, which have a wave nature, in the propagation of radiation in an inhomogeneous medium are found. It is shown that the dispersion of the angle of rotation of the polarization plane increases with distance and can be determined from measurements of the degree of polarization of radiation.