Patent ID: 6360565
Filing Date: 2002-03-26
Classification: C03B,G02B

Abstract:
A method of making an optical fiber comprising:forming an optical fiber draw blank having a glass core of refractive index n1 surrounded by a cladding glass layer of refractive index n2, said blank having apertures diametrically opposed with respect to said core and spaced from said core, said apertures extending longitudinally through said blank and parallel to said core, said core glass having a viscosity at a draw temperature and said cladding glass having a viscosity at the draw temperature higher than the viscosity of said core glass at the draw temperature, and said draw blank having low viscosity glass layer between said core and said apertures, said low viscosity glass having a viscosity at the draw temperature not greater than the viscosity of said core glass and less than the viscosity of the cladding glass layer and said low viscosity glass having a refractive index n3, heating a portion of said draw blank to the draw temperature, and drawing an optical fiber from said draw blank at such a rate that said core glass and said low viscosity glass flow toward said apertures and said apertures close to form a core having an elliptical cross-section in which said low viscosity glass layer has a major axis radius b2, a minor axis radius a2, and an aspect ratio b2/a2 and the core glass has a major axis radius b1, a minor axis radius a1 and an aspect ratio b1/a1, wherein the aspect ratio b1/a1 is greater than the aspect ratio b2/a2.