Method of producing a glass preform

Abstract

In a glass preform ( 10 ) to be subjected to fiber-drawing, use is made of a cylindrical glass tube ( 21 ) whose one end in an axial direction is sealed. A plurality of glass capillaries ( 22 ) extend in the glass tube in the axial direction. The glass capillaries are fused to one another into an integral structure. The glass capillaries have air holes periodically arranged on a plane perpendicular to the axial direction, respectively.

1 - 10 . (canceled)  
   
   
       11 . A method of producing a glass preform, comprising the steps of: 
 preparing a cylindrical glass tube whose one end in an axial direction is sealed;    disposing a plurality of glass capillaries in the glass tube; and    heating the glass tube with its interior kept in a reduced-pressure condition.    
   
   
       12 . The method according to  claim 11 , wherein a tubular member having an internal cavity and longitudinal opposite ends both of which are sealed is used as each of the glass capillaries.  
   
   
       13 . The method according to  claim 11 , comprising the steps of: 
 preparing, as each of the glass capillaries, a tubular member having a longitudinal one end and the other end which are sealed and opened, respectively.    
   
   
       14 . The method according to  claim 11 , further comprising the step of disposing at least one glass rod in the glass tube.  
   
   
       15 . The method according to  claim 14 , further comprising the step of using, as the at least one glass rod, a tubular member having longitudinal opposite ends which are opened.  
   
   
       16 . The method according to  claim 14 , further comprising the steps of: 
 using, as the at least one glass rod, a tubular member having a longitudinal one end and the other end which are sealed and opened, respectively, and    facing the longitudinal one end of the tubular member to the one end of the glass tube.    
   
   
       17 . The method according to  claim 14 , further comprising the steps of: 
 using, as the at least one glass rod, a tubular member a longitudinal one end and the other end which are sealed and opened, respectively, and    facing the other end of the tubular member to the one end of the glass tube.    
   
   
       18 . The method according to  claim 14 , further comprising the step of using, s the at least one glass rod, a solid member without an internal cavity.  
   
   
       19 . The method according to  claim 14 , further comprising the step of using, as the at least one glass rod, a tubular member having an internal cavity and longitudinal opposite ends both of which are sealed.  
   
   
       20 . The method according to  claim 14 , wherein each of the glass capillaries and the glass rod is made of a multi-component glass.  
   
   
       21 . The method according to  claim 14 , wherein each of the glass capillaries and the glass rod is made of a borosilicate glass.  
   
   
       22 . The method according to  claim 14 , wherein each of the glass capillaries and the glass rod is made of a glass containing, by mass %, 55-95% SiO 2 , 1-30% B 2 O 3 , and 0.1-10% Na 2 O.  
   
   
       23 . The method according to  claim 14 , wherein each of the glass capillaries and the glass rod is made of a glass essentially consisting of, by mass %, 55-95% SiO 2 , 1-30% B 2 O 3 , and 0.1-10% Na 2 O, 0-10% Al 2 O 3 , 0-5% CaO, 0-10% BaO, and 0-5% K 2 O.  
   
   
       24 . The method according to  claim 14 , wherein each of the glass capillaries and the glass rod is made of a glass without absorption of light having a wavelength of 1400 nm by OH groups.  
   
   
       25 . The method according to  claim 14 , wherein each of the glass capillaries and the glass rod has a refeactive index (nd) between 1.45 and 2.00.  
   
   
       26 . (canceled)