| 摘要 |
PURPOSE:To vary the refractive index distribution of a fiber freely after its manufacture by releasing residual stress by making the coefficient of viscosity of one of clad layers at high temperature larger than the coefficient of a core and leaving residual stress at the time of drawing. CONSTITUTION:The core part in the center as a preform for an optical fiber is SiO2 glass doped with about 2.5wt.% GeO2, a 1st clad part around the core part is pure SiO2 glass, and a 2nd clad part around the 1st clad part is SiO2 glass doped with 0.6wt.% chlorine. This preform is drawn with varied drawing force to obtain the fiber which has an about 11.5mum core diameter, an about 40mum 1st clad diameter, and an about 125mum 2nd clad diameter. When the drawing tensile force is set to 20, 100, and 250g, the specific refractive index difference between the core 1 and 1st clad 2 is 0.15, 0.2, and 0.30% and the specific refractive index difference between the 1st clad 2 and 2nd clad 2 is 0.04, 0.09, and 0.19%. The difference of the refractive index distribution is caused by elastic effect due to the residual stress in the optical fiber and the 1st clad 1 is put in charge of much of the drawing strain. |
