U.S. Philips Corporation

Rene A Pluijms

Johannes M Van Esdonk

Gerrit J Koel

Jan G Peelen

Johannes P De Meij

Jacob W De Ruiter

Emmanuel Papanikolau

Hubertus J Schrans

Leendert B Jongeling

Pieter Van Der Ree

The invention relates to a method of manufacturing optical fibres in which a quartz glass tube is coated on the inside with core material, the assembly is contracted to form a solid rod which is then inserted into a quartz glass tube, after which the assembly is drawn. The last tube is thermally treated to eliminate contaminations at the surface which may detrimentally influence the tensile strength of the ultimate fibre.

Method of manufacturing optical fibres having a core and a cladding of

While collapsing the central duct in hollow glass optical fiber preforms, an etchant consisting of a mixture of oxygen and a fluorocarbon compound from the group C.sub.2 F.sub.6, C.sub.3 F.sub.8 and N-C.sub.4 F.sub.10 is passed through the duct. In particular, the etchant is passed through the duct only when the duct's diameter is 1 mm or smaller. The resulting solid preforms and optical fibers drawn therefrom do not have a central dip in the refractive index profile.

Method of manufacturing an optical fiber preform

Solid glass preforms are made by externally heating a tubular preform by a plasma which is reciprocated along the hollow tube. The plasma gas consists entirely or partly of a molecular gas (N.sub.2 or O.sub.2, for example). The hollow preform is preferably rotated during collapsing.

Method of manufacturing solid glass preforms from hollow preforms

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Eindhoven, Netherlands

Rene A Pluijms