OPTICAL FIBER AND ITS MANUFACTURE

摘要

PURPOSE:To improve wide-band characteristics and transmission characteristics by adding fluorine between a core and a clad and forming an intermediate layer which has a lower refractive index than the clad, and adding fluorine to the core as well and varying the refractive index between the intermediate layer and core. CONSTITUTION:Gaseous raw materials for glass formation are mixed and supplied to a multiple-tube burner. Combustion gas and combustion improving gas are supplied to its outside to cause flame hydrolysis reaction. Produced glass particulates are deposited to grow a porous base material axially, and the refractive index is increased gradually to the center. At the same time, fluorine is added uniformly to the porous base material to form the core 1 outside of the part corresponding to the core 1 and the intermediate layer which has a continuous refractive index distribution and is lower in refractive index than the clad 3. The obtained porous base material is heated and sintered in an inert gas atmosphere to form a transparent preform. Then, the material is inserted into a quartz tube as the clad 3, and heated and drawn to obtain a thin optical fiber.