Process for manufacturing optical-fibre preforms at high deposition rate

Claim 1

A process for producing optical fibers which comprises the steps of: forming a preform by: producing glass particles by a reaction between vapor-phase reactants, rotating a supporting glass tube having an internal surface around its axis, initiating said reaction between the reactants in an input end of the tube in a region with constant temperature Ti, simultaneously depositing said glass particles along an entire length L of the tube by heating the tube over its entire length L at once to a temperature T(r,x) which is a function of the distance from the input end given by the relationship: ##EQU5## where: exp represents the natural exponent base and the parenthetical expression the power thereof, T(r,x) is the temperature of the tube at a distance r from the axis, where r is the internal tube radius, and at a distance x from the input end, T i is the temperature at the input end of the tube, v x is the axial component of the speed of the glass particles entrained through said tube by a gas, L represents the distance from the input end of tube at which all the particles have been deposited, γ is the kinematic viscosity of vapor flow in the tube, X varies from X=O to X=L, and K is a proportionality coefficient, so as to obtain a layer of deposited particles with constant thickness; thermally collapsing said preform; and drawing said fibers from the collapsed tube.