| 摘要 |
PURPOSE:To easily obtain the title NA-conversion optical fiber wherein the refractive index of the core is periodically changed in the longitudinal direction by forming a clad glass having the softening temp. lower than that of a core glass on the outside of the core glass, and drawing the glasses while changing the drawing tension at a specified cycle. CONSTITUTION:The clad glass having the softening temp. lower than that of the core glass is formed on the outside of the core glass to form an optical fiber preform. The preform is then drawn while changing the drawing tension at a specified cycle to obtain an NA-conversion optical fiber. As the means for changing the drawing tension, the drawing temp. is changed, for example, while fixing the drawing rate. Since the low-softening-temperature glass is used as the clad glass, all the stress during the drawing is exerted on the core, and an optical fiber wherein the refractive index of the core is periodically changed in the longitudinal direction can be obtained. |
