Patent ID: 6697559
Filing Date: 2004-02-24
Classification: C03C,G02B

Abstract:
An optical fiber, composed of silica glass, having a center core region, a ring core region doped with germanium dioxide and has a maximum concentration thereof, and a cladding region, all of which are arranged concentrically, the refractive index of said center core region being lower than that of said ring core region;wherein a region located adjacent to said ring core region is doped with fluorine element and having a maximum concentration thereof; and said region doped with fluorine element has a boundary portion at an edge of said ring core region, the thickness of said boundary portion is at least 1 &mgr;m, the boundary portion has a concentration of germanium dioxide that is less than the maximum concentration of germanium dioxide in said ring core region, and the concentration of fluorine element in said boundary portion is less than the maximum concentration of fluorine in said region doped with fluorine.