Method of fabricating optical fibers

Claim 1

A method of manufacturing an optical fiber, said method comprising the steps of: providing a glass tube having an inner wall; heating the tube to a temperature between 1100° and 1300° C.; passing a reactive glass-forming gas mixture at a pressure between 1 and 30 hPa through the tube; moving a nonisotherml plasma back and forth in the tube between two reversal points to react the gas mixture to deposit glass layers on the inner wall of the glass tube without the formation of glass soot; collapsing the tube with the glass layers to produce a solid preform; and drawing the solid preform into an optical fiber; characterized in that: the plasma extends along part of the length of the tube; and in an end region adjacent a reversal point, the extent of the plasma is changed as a function of time, said region having a length sufficient to reduce end taper in the preform.

Claim 2

A method of manufacturing an optical fiber, said method comprising the steps of: providing a glass tube having an inner wall; heating the tube to a temperature between 1100° and 1300° C.; passing a reactive glass-forming gas mixture at a pressure between 1 and 30 hPa through the tube; moving a nonisotherml plasma back and forth in the tube between two reversal points to react the gas mixture to deposit glass layers on the inner wall of the glass tube without the formation of glass soot; collapsing the tube with the glass layers to produce a solid preform; and drawing the solid preform into an optical fiber; characterized in that: the plasma extends along part of the length of the tube; and in an end region adjacent a reversal point, the extent of the plasma is changed as a function of time, said region having a length sufficient to reduce end taper in the preform.

Claim 5

A method of manufacturing an optical fiber, said method comprising the steps of: providing a glass tube having an inner wall; heating the tube to a temperature between 1100° and 1300° C.; passing a reactive glass-forming gas mixture at a pressure between 1 and 30 hPa through the tube; moving a nonisothermal plasma back and forth in the tube between two reversal points to react the gas mixture to deposit glass layers on the inner wall of the glass tube without the formation of glass soot; collapsing the tube with the glass layers to produce a solid preform; and drawing the solid preform into an optical fiber; characterized in that: in a first end region adjacent a reversal point, the plasma is moved nonlinearly as a function of time, said end region having a length sufficient to reduce end taper in the preform; and the plasma is moved linearly as a function of time between the first end region and a second end region adjacent the other reversal point.

Claim 6

A method of manufacturing an optical fiber, said method comprising the steps of: providing a glass tube having an inner wall; heating the tube to a temperature between 1100° and 1300° C.; passing a reactive glass-forming gas mixture at a pressure between 1 and 30 hPa through the tube; moving a nonisothermal plasma back and forth in the tube between two reversal points to react the gas mixture to deposit glass layers on the inner wall of the glass tube without the formation of glass soot; collapsing the tube with the glass layers to produce a solid preform; and drawing the solid preform into an optical fiber; characterized in that: in a first end region adjacent a reversal point, the plasma is moved nonlinearly as a function of time, said end region having a length sufficient to reduce end taper in the preform; and the plasma is moved linearly as a function of time between the first end region and a second end region adjacent the other reversal point.

Claim 9

A method of manufacturing an optical fiber, said method comprising the steps of: providing a glass tube having an inner wall; heating the tube to a temperature between 1100° and 1300° C.; passing a reactive glass-forming gas mixture at a pressure between 1 and 30 hPa through the tube; moving a nonisothermal plasma back and forth in the tube between two reversal points to react the gas mixture to deposit glass layers on the inner wall of the glass tube without the formation of glass soot; collapsing the tube with the glass layers to produce a solid preform; and drawing the solid preform into an optical fiber; characterized in that: the plasma extends along part of the length of the tube; in an end region adjacent a reversal point, the plasma is moved nonlinearly as a function of time and/or the extent of the plasma is changed as a function of time, said end region having a length from 2 to 40% of the distance between the reversal points; and the reactive gas mixture is passed through the tube at a rate satisfying the relationship ##EQU6## where Q T is the total flow of the gas mixture in cubic centimeters per minute referred to standard conditions of 273K and 1013 hPa (sccm), Q SiCl .sbsb.4 is the flow of SiO 2 -forming chlorides in the gas mixture in sccm, m SiO .sbsb.2 is the deposition rate of SiO 2 in grams per minute, and Z p is the distance between the reversal points in meters, and where Q T is chosen to be as small as possible while satisfying this relationship.

Claim 10

A method of manufacturing an optical fiber, said method comprising the steps of: providing a glass tube having an inner wall; heating the tube to a temperature between 1100° and 1300° C.; passing a reactive glass-forming gas mixture at a pressure between 1 and 30 hPa through the tube; moving a nonisothermal plasma back and forth in the tube between two reversal points to react the gas mixture to deposit glass layers on the inner wall of the glass tube without the formation of glass soot; collapsing the tube with the glass layers to produce a solid preform; and drawing the solid preform into an optical fiber; characterized in that: the plasma extends along part of the length of the tube; in an end region adjacent a reversal point, the plasma is moved nonlinearly as a function of time and/or the extent of the plasma is changed as a function of time, said end region having a length from 2 to 40% of the distance between the reversal points; and the reactive gas mixture is passed through the tube at a rate satisfying the relationship ##EQU6## where Q T is the total flow of the gas mixture in cubic centimeters per minute referred to standard conditions of 273K and 1013 hPa (sccm), Q SiCl .sbsb.4 is the flow of SiO 2 -forming chlorides in the gas mixture in sccm, m SiO .sbsb.2 is the deposition rate of SiO 2 in grams per minute, and Z p is the distance between the reversal points in meters, and where Q T is chosen to be as small as possible while satisfying this relationship.