Manufacture of optical fiber base material

Abstract

Abstract PURPOSE:To obtain an optical fiber base material having a lowered refractive index in the vicinity of the outside by heat treating a porous glass preform obtd. by a vapor phase axial sticking method in an atmosphere of a lower refractive index dopant to adjust the refractive index distribution. CONSTITUTION:Sootlike glass fine particles are stuck and deposited on the lower end of a rodlike substrate rotating and moving upward by a vapor phase axial sticking method, and while pulling up the substrate the particles are grown in the axial direction to form a rodlike porous glass preform. The preform is then heat treated in an atmosphere of a lower refractive index dopant such as fluoride or boron compound. By this treatment vapor of the dopant is diffused in the preform, and bonding occurs in the vicinity of the outside of the preform. As a result, the refractive index in the vicinity of the outside is lowered to give a square distribution type profile.

Inventors

• 👤 Masao Kawachi
• 👤 Kazuo Sanada
• 👤 Koichi Inada
• 👤 Takeru Fukuda
• 👤 Takao Shioda

Bibliographic Details