Method and apparatus for fabricating silica based glass

Abstract

A method for fabricating fluorine doped, silica based glass and fiber by depositing a layer of high purity silica soot on a core rod while rotating the core rod places the rod of pure fused silica or doped fused silica and silica soot in a furnace having a lining of Al 2 O 3 , elevates the temperature in a fluorine rich atmosphere to establish the proper differential in the indices of refraction between the core start rod and the deposited layer, and heats the resulting rod at consolidation temperatures in an atmosphere of helium to form a preform. The apparatus includes a furnace having a lining of high purity alumina that is resistant to chemical etching and change normally due to the fluorine and chlorine.

1 - 15 . Cancelled  
     
     
         16 . A method of making a silica-based glass in a structure having an interior and an interior surface, comprising the steps of: 
 a. depositing silica soot onto a workpiece;    b. drying the silica soot; and    c. sintering the silica soot in the interior of the structure, the interior surface of the structure comprising aluminum oxide, and the aluminum oxide having a concentration of at least about 99.97% facing the soot.    
     
     
         17 . The method of  claim 16  wherein the surface of aluminum oxide has a potassium content of less than one part per million, a calcium content of no more than approximately one part per million, a silicon content of no more than approximately twenty-eight parts per million, and a magnesium content of no more than approximately two hundred and fifty parts per million.  
     
     
         18 . The method of  claim 16 , substantially all of the structure being a muffle, and the aluminum oxide having a visual transmittance of 96%.  
     
     
         19 . The method of  claim 16  wherein the sintering step is performed in the presence of helium.  
     
     
         20 . The method of  claim 16  wherein the drying step is performed in the presence of chlorine.  
     
     
         21 . The method of  claim 16  wherein the drying and sintering steps are performed in the presence of chlorine and helium.  
     
     
         22 . The method of  claim 16  wherein the workpiece is a start rod.