Abstract: A grating made in the core of an optical fiber presents a nonuniform and asymmetrical profile of the modulation of the refractive index in the direction of the length, which profile is represented by a curve that rises gradually and monotonically from a minimum and substantially null value, with substantially horizontal tangent, in correspondence with an end of the grating to a maximum value, also with substantially horizontal tangent, which is reached in correspondence with the other end of the grating.

Abstract: In order to fabricate strip monomode active optical waveguides for optical elecommunications, a layer of vitreous soot is deposited on a substrate and is impregnated with a solution of a precursor of a rare-earth dopant, and a radiation with a wavelength comprised in an absorption band of the dopant is moved along the soot, along a trajectory corresponding to the geometrical shape desired for the guide, thereby forming a vitrified strip.

Abstract: In order to fabricate strip monomode active optical waveguides for optical telecommunications, a layer of vitreous soot is deposited on the interior of a tubular substrate and is impregnated with a solution of a precursor of a rare-earth dopant, and a radiation with a wavelength comprised in an absorption band of the dopant is moved along the soot, along a trajectory corresponding to the geometrical shape desired for the guide, thereby forming a vitrified strip.

Abstract: Silica intended to form the core of an optical-fibre preform is deposited as an unvitrified soot inside a reaction tube, where a non-aqueous solution of dopant precursor(s) is then introduced without removing the tube from the lathe. The precursor(s) of the dopant(s) are dissolved in an anhydrous organic solvent. The solution containing the dopant precursor(s) is introduced into the reaction tube without removing the tube from the lathe so that the solution covers the whole surface of the deposited soot layer and impregnation of the deposited soot layer occurs.