Consequences of TiO2 doping on the optical properties of porous silica layers coated on silica optical fibers

The paper deals with the investigation of optical properties of porous sili ca and TiOTi chains - doped porous silica layers coated on silica optical f ibers. The porous layers composed of dried gels have been prepared by the s ol-gel method from alkoxides. The refractive indices and optical attenuatio n of the layers have been determined from the measured angular distribution s of the output optical power. For this purpose, a model based on geometric al optics has been developed. The interaction of the porous layers with ben zene, toluene, xylene and hexane has been investigated by measuring the cha nges of the output optical power induced by the effect of vapors of the hyd rocarbons in ail. On the basis of these measurements, the porosity of the l ayer, partition coefficients and equilibrium adsorption constants of the hy drocarbons have been estimated. The measured decrease of the optical power for the aromatic hydrocarbons and the increase of the output power for the aliphatic hydrocarbon have been explained on the basis of the developed mod el. (C) 1999 Elsevier Science S.A. All rights reserved.