Investigation of the sensitivity of PCS fibers to changes of light absorption coefficient of the cladding

Abstract

In the paper the sensitivity of polymer-clad silica (PCS) fibers to changes of light-absorption coefficient in the evanescent-wave area are investigated both theoretically and experimentally. The theoretical analysis was carried out on the basis of a ray-optic model taking into account changes of the complex refractive index of the fiber cladding. Values of the complex refractive index estimated from spectral and refractive-index measurements with water/glycerol solutions of methylene blue were used in the analysis. Results calculated for the excitation of the fiber from axial light sources or by using inclined beams are shown in the paper and compared with experimental results.