OPTICAL FIBER BILLET HAVING A BARRIER FOR RADICAL "OH" AND METHOD OF ITS MANUFACTURE Russian patent published in 2004 - IPC

FIELD: "OH" having a barrier for a radical "OH". SUBSTANCE: the invention is pertinent to an optical fiber billet formed with use of process MCVD ( modified settling from a gas phase), and to put it more precisely - to the optical fiber billet having a barrier for a radical "OH" and to a method of its manufacture. The purpose of the invention is creation of an improved optical fiber billet, an improved method of its manufacture, and also creation of a billet of an optical fiber from which it is possible to produce an optical fiber having the low optical losses, caused by presence of a hydroxyl group. In the process of such an optical fiber billet manufacture, according to the true invention, the first "OH" - barrier and the second "OH" - barrier, being free from P₂O₅, are settling accordingly between a tube-substrate and a layer of a shell and also between the layer of the shell and the layer of the optical fiber core during the depositing process. Besides the index of refraction is increasing in the direction to the center of the layer of the optical fiber core. The first or second barriers are formed out of SIO₂ or SiO₂ + GeO₂ and have an index of refraction of no more than the index of refraction of the tube-substrate and the layer of the optical fiber core. The index of refraction on the periphery of the layer of the optical fiber core makes 75-99 % from against the index of refraction in the center of the layer of the optical fiber core. EFFECT: the invention allows to create an improved optical fiber billet with low optical losses an improved method of its manufacture. 13 cl, 3 dwg