Patent ID: 6062046
Filing Date: 2000-05-16
Classification: C03B,G02B

Abstract:
wherein said third step includes:a first sub-process of forming an inner soot body to be an inner core of said third core portion after vitrification around the outer periphery of said first soot body, said inner core being positioned around the outer periphery of said second core portion and having a mean relative refractive index difference with respect to said cladding portion of a fourth value .DELTA.n.sub.3a smaller than the second value .DELTA.n.sub.2 ; anda later process of forming an outer soot body to be an outer core of said third core portion after vitrification around an outer periphery of said inner soot body, said outer core being positioned around an outer periphery of said inner core and having a mean relative refractive index difference with respect to said cladding portion of a fifth value .DELTA.n.sub.3b greater than the fourth value .DELTA.n.sub.3a and smaller than the second value .DELTA.n.sub.2, andwherein, in said sixth step, said optical fiber perform obtained at said fifth step is drawn so as to yield a single-mode optical fiber in which said inner and outer cores of said third core portion have outer diameters of c.sub.a and c greater than c.sub.a, respectively, and said inner and outer cores satisfy the following relationship:0.1.ltoreq.(c.sub.a -b).multidot.(.DELTA.n.sub.3b -.DELTA.n.sub.3a)/(c.multidot..DELTA.n.sub.3b).ltoreq.0.8therebetween.