Interaction of radiation with an absorbing medium in a section of a sharply bent fiber waveguide

Theoretical and experimental investigations were made of the interaction of radiation, channeled by a fiber waveguide, with an absorbing external medium in the region of a sharp bend of the waveguide. A theory is based on the formalism of the Fresnel reflection coefficients together and on the angular intensity distribution function in the region of the bend. The dependences of the signal at the output of the fiber waveguide on the absorption by the medium and on its dispersion are obtained. A method is suggested for separating the two components of such signals. Experimental separation is reported of the signal representing the anomalous dispersion of an absorption line of a solution of rhodamine C in water. The angular distribution functions are obtained in the region of a bend. The theory is shown to explain well the experimental results.