Process for the manufacture of optical fibers with a radial refractive index

US4165222A · kind A · utility

Assignee

• Thomson-CSF · FR

Inventors

• Arnaud de Panafieu · Paris, FR
• Michel Villard · Paris, FR
• Christiane Baylac · Paris, FR
• Michel J. Favre · Chantilly, FR

Key dates

• Filing date: Oct 14, 1977
• Grant date: Aug 21, 1979
• Expiry date: Oct 14, 1997

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C03C23/008
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A process yielding a glass blank in the form of a rod intended for drawing an optical fiber of the kind of self-focussing fiber i.e. having a radial refractive index gradient, having features (substantially transparency or transmission efficiency) lower than those of the fibers intended for long distance communication but sufficient for middle distance transmission, and which exhibits a lower cost than known processes. In a first stage a phase separation yields a "hard" phase (rich in silicon) and a "soft" phase (poor in silicon and rich in impurities) due to the drawing of a rod from a bath of molten glass through a cooling system having a strong temperature gradient and creating a radial refractive index gradient. In a second stage the soft phase is leached, eliminating the impurities contained in the soft phase but keeping safe the radial gradient. In a third stage a consolidation treatment is a pure annealing treatment rendering the hard phase more homogeneous.