Method for producing base material for optical fiber having deformed first clad, base material for optical fiber and optical fiber

Abstract

There is disclosed a method for producing a base material for optical fiber having a deformed first clad consisting of at least a core, a first clad and a second clad, comprising a step of deforming a shape of a section of the first clad so that it may have at least one linear part when the first clad is formed around the core, a step of depositing porous glass fine particles as the second clad made of the same material as that of the first clad on a glass rod having the deformed first clad to form a porous glass base material, and a step of forming the second clad having a round section by vitrifying it. There can be provided a method for producing a base material for optical fiber wherein a lot of breakages or cracks on the surface of the base material can be prevented in a step of depositing porous glass fine particles for the second clad on the first clad, and base material for optical fiber having no defects, and an optical fiber having an efficient effect of being excited with excitation light.

1 . A quartz base material for an optical fiber having a deformed first clad consisting of at least three refractive index area, namely a core, a deformed first clad and a second clad wherein a section of the first clad has a deformed shape with at least one linear part and the second clad has a round section, and the main material of the first clad and the second clad are the same, and a length of the longest part of the deformed section of the first clad is 15 mm or less.  
   
   
       2 . The base material for an optical fiber having a deformed first clad according to  claim 1  wherein the shape of the section of the first clad is D-shape, a square shape or a drum shape.  
   
   
       3 . The base material for an optical fiber having a deformed first clad according to  claim 1  wherein the refractive index of the first clad is distributed so that it may gradually decreases from the center to the periphery.  
   
   
       4 . The base material for an optical fiber having a deformed first clad according to  claim 2  wherein the refractive index of the first clad is distributed so that it may gradually decreases from the center to the periphery.  
   
   
       5 . An optical fiber having a deformed first clad produced by wiredrawing the base material for optical fiber according to  claim 1 .  
   
   
       6 . An optical fiber having a deformed first clad produced by wiredrawing the base material for optical fiber according to  claim 2 .  
   
   
       7 . An optical fiber having a deformed first clad produced by wiredrawing the base material for optical fiber according to  claim 3 .  
   
   
       8 . An optical fiber having a deformed first clad produced by wiredrawing the base material for optical fiber according to  claim 4.