Method of manufacturing optical fiber base material and apparatus of the same

Abstract

A method of manufacturing an optical fiber base material includes: forming a porous glass base material by depositing glass particles; providing a synthetic quartz glass vessel at least partly made of quartz glass which contains aluminum equal to or less than 0.01 ppm; introducing dehydration reaction gas and inert gas into the vessel; heating a portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm in the vessel that contains the dehydration reaction gas and the inert gas; and inserting the porous glass base material into the heated vessel to dehydrate and sinter the porous glass base material.

1 . A method of manufacturing an optical fiber base material, comprising:
 forming a porous glass base material by depositing glass particles;   providing a vessel at least partly made of quartz glass which contains aluminum equal to or less than 0.01 ppm;   introducing dehydration reaction gas and inert gas into the vessel;   heating a portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm in the vessel containing the dehydration reaction gas and the inert gas; and   inserting the porous glass base material into the heated vessel to dehydrate and sinter the porous glass base material.   
   
   
       2 . The method according to  claim 1 , wherein the portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm in the vessel that is formed by melting a soot deposit, the soot deposit being formed by depositing glass particles which are produced by hydrolyzing silicide with oxyhydrogen flame. 
   
   
       3 . The method according to  claim 2 , wherein the silicide includes any of SiCl 4 , (CH 3 )SiCl 3 , (CH 3 ) 2 SiCl 2  or a mixed compound thereof. 
   
   
       4 . The method according to  claim 1 , wherein the portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm is larger than at least an area heated by a heat source in the heating. 
   
   
       5 . The method according to  claim 1 , wherein in the dehydrating and sintering, a total amount of time over which the vessel is subjected to a temperature exceeding 1,400 degrees Celsius is within a time period over which a glass layer is entirely crystallized in a depthwise direction in at least a part of the portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm in the vessel. 
   
   
       6 . The method according to  claim 1 , wherein in the dehydrating and sintering, a total amount of time over which the vessel is subjected to a temperature exceeding 1,400 degrees Celsius is within a time period obtained by multiplying a thickness (mm) of the quartz glass which contains aluminum equal to or less than 0.01 ppm in the vessel by 1,500 hours. 
   
   
       7 . The method according to  claim 1 , wherein a pressure in the vessel is adjusted in the heating and the dehydrating and sintering. 
   
   
       8 . The method according to  claim 7 , wherein the heating and the dehydrating and sintering further includes alerting when the pressure in the vessel is out of a predetermined range. 
   
   
       9 . The method according to  claim 7 , wherein the heating and the dehydrating and sintering further includes measuring a pressure in the vessel and controlling an outlet flow in order that the pressure in the vessel be within a predetermined range. 
   
   
       10 . The method according to  claim 7 , wherein the heating and the dehydrating and sintering further includes alerting when a difference in pressure between the inside of the vessel and a portion adjacent to a heat source outside the vessel. 
   
   
       11 . The method according to  claim 7 , wherein the heating and the dehydrating and sintering further includes measuring a difference in pressure between the inside of the vessel and a portion adjacent to a heat source outside the vessel and controlling an outlet flow in order that the measured difference in pressure be within a predetermined range. 
   
   
       12 . An apparatus for dehydrating and sintering a porous glass base material for an optical fiber, comprising:
 a heat source;   a furnace tube at least partly made of quartz glass which contains aluminum equal to or less than 0.01 ppm;   a gas introducing port that introduces gas to the furnace tube; and   a gas discharging port that discharges gas from the furnace tube.   
   
   
       13 . The apparatus according to  claim 12 , wherein the part made of quartz glass which contains aluminum equal to or less than 0.01 ppm in the furnace tube is formed by melting a soot deposit, the soot deposit being formed by depositing glass particles which are produced by hydrolyzing silicide with oxyhydrogen flame. 
   
   
       14 . The apparatus according to  claim 13 , wherein the silicide includes any of SiCl 4 , (CH 3 )SiCl 3 , (CH 3 ) 2 SiCl 2  or a mixed compound thereof. 
   
   
       15 . The apparatus according to  claim 12 , wherein an area heated by at least a heat source is larger than the portion made of quartz glass which contains aluminum equal to or less than 0.01 ppm. 
   
   
       16 . The apparatus according to  claim 12  further comprising:
 an intra-furnace tube pressure measuring unit that measures a pressure in the furnace tube; and   a pressure control mechanism that adjusts a pressure in the furnace tube.   
   
   
       17 . The apparatus according to  claim 16 , wherein the pressure control mechanism includes an alarm unit that alerts when the pressure measured by the intra-furnace tube pressure measuring unit is out of a predetermined range. 
   
   
       18 . The apparatus according to  claim 16 , wherein the pressure control mechanism include:
 an automatic valve provided on the gas discharging port; and   a control unit that controls a flow rate of the automatic valve in order that the pressure measured by the intra-furnace tube pressure measuring unit be within a predetermined range.   
   
   
       19 . The apparatus according to  claim 16  further comprising an extra-furnace tube pressure measuring unit that measures a pressure around a heat source outside the furnace tube, wherein the pressure control mechanism includes an alarm unit that alerts when a difference between the pressure measured by the intra-furnace tube pressure measuring unit and the pressure measured by the extra-furnace tube pressure measuring unit is out of a predetermined range. 
   
   
       20 . The apparatus according to  claim 16  further comprising an extra-furnace tube pressure measuring unit that measures a pressure adjacent to a heat source outside the furnace tube, wherein
 the pressure control mechanism includes:   an automatic valve provided on the gas discharging port; and   a control unit that controls a flow rate of the automatic valve in order that a difference between the pressure measured by the intra-furnace tube pressure measuring unit and the pressure measured by the extra-furnace tube pressure measuring unit be within a predetermined range.   
   
   
       21 . The apparatus according to  claim 12  further comprising:
 a shaft that supports a porous glass base material; and   a convection preventing plate that is mounted adjacent to a porous glass base material mounting part of the shaft.