Electric furnace extension method and extension apparatus for optical fiber glass preform

Abstract

An electric furnace extending method and apparatus for an optical fiber glass body alignment when connecting the extension use body and pulling member and making it possible to immediately start the extension after the fusing of the connection portion. A centering mechanism for centering the free end portion of the body and member on the furnace center side is provided between the furnace pipe of the electric furnace and grips of the extension use glass body and between the furnace pipe and the pulling member. The free end portion is centered by this centering mechanism, then the gripped sides of the body and member are fixed, the front ends of the two free end portions are abutted and fused and bonded at the highest temperature portion inside the electric furnace, then the highest temperature portion is moved to the extension portion of the glass body side and the extending of the glass body is commenced.

What is claimed is:  
     
         1 . An apparatus for extending an optical fiber body, comprising: 
 an upper holder for holding an upper end of an extension optical fiber glass body to be extended;    a lower holder, provided at a position coinciding with an axial center of said upper holder and facing said upper holder, said lower holder holding a lower end of a pull glass member connected to a lower end of the extension optical fiber glass body, an axial center of said pull glass member coinciding with an axial center of said extension optical fiber glass body, and said lower holder being pulled toward a lower portion in response to an extension of said extension optical fiber glass body;    an electric furnace provided between said upper holder and said lower holder and which heats said extension optical glass preform;    a moving means moving at least said lower holder toward a low position to pull said extending optical fiber glass preform; and    a control means, wherein    said control means controls the following, when extending said optical fiber glass preform in said electric furnace, and after joining of the lower end of said optical fiber glass preform and the upper end of said pull glass member by heat-melting manner,    moving the maximum temperature portion of said electric furnace to a joined portion to heat and connect the joined portion, and    controlling said movement means to lower said lower holder, and to move the maximum temperature portion of said electric furnace from said joined portion to the extending portion of said optical fiber glass body.    
     
     
         2 . An apparatus for extending an optical fiber body according to  claim 1 , wherein a dummy member is connected to the lower end of said extension optical fiber glass body, a diameter of a lower tip of said dummy member being smaller than a diameter of the upper tip of said pulling glass member, a diameter of an upper tip of said dummy member being substantially equal to or close to a diameter of said extension optical fiber glass body, said dummy member has a semi-conical shape in the upper tip and said dummy member being formed by a material equal to that of said extension optical fiber glass body, and 
 wherein said control means controls the movement of said moving means to move said lower holder downward to extend said extension optical fiber glass body connected to said dummy member at the lower tip thereof.    
     
     
         3 . An apparatus or extending an optical fiber body according to  claim 2 , wherein said diameter of said lower tip of said dummy member is approximately ½ to ⅓ of the diameter of said upper end of said pulling glass member.