British Telecommunications Public Limited Company

British Telecommunications Corporation

John R Williams

Paul W France

Steven F Carter

Steven T Davey

Daryl Szebesta

The surface quality of halide, preferably fluoride, articles, e.g., articles used in the preparation of halide fibers is improved by cleaning the surface with an aqueous etchant and thereafter removing the etchant by washing the surface with methanol. The aqueous etchant is preferably a solution which contains hydrochloric acid and zirconium oxychloride.

Etching a halide glass tube, removing the etchant, and forming an optical fiber

The surface quality of halide, preferably fluoride, articles, e.g. articles used in the preparation of halide fibres is improved by cleaning the surface with an aqueous etchant and thereafter removing the etchant by washing the surface with methanol. The aqueous etchant is preferably a solution which contains hydrochloric acid and zirconium oxychloride.

Surface treatment of halide glass articles

Halide glass articles, e.g. rods, tubes and preforms for making fluoride glass fibres, are prepared by melting and/or casting the articles under a low pressure, e.g. 0.01 to 500 mbars and, during the low pressure regime, a gas flow rate of between 0.01 to 100 liters/min (measured at NTP) is maintained. It has been found that subjecting the melts to a low pressure reduces the attenuation of the fibre which eventually results from the melts.

Method of making halide fibers including casting under a reduced pressure

Method for the preparation of halide glass articles

A process for treating a halide, e.g. fluoride, glass composition, characterized by contacting a melt of the composition (3) with dry oxygen (6). Oxygen, simply on contact with a fluoride glass melt, converts transition metals, e.g. from Fe(II) to Fe(III), from one stable state to another and thereby reduces loss at transmission wavelengths in optical fibre, e.g. the loss at 2.6 .mu.m attributabel to Fe(II).

Method of preparing a halide optical fibre

A high numerical aperture optical fibre, e.g. for use in remote spectroscopy, has a cladding of a halide glass which contains Hf and a core of a halide glass which contains Pb. Preferably both glasses contain ZrF.sub.4, BaF.sub.2, LaF.sub.3, AlF.sub.3 and NaF. In addition the cladding contains HfF.sub.4 but no PbF.sub.2 and the core contains PbF.sub.2 but no HfF.sub.4.

Halide fibre with high numerical aperture

A process for treating a halide, e.g. fluoride, glass composition, characterized by contacting a melt of the composition with dry oxygen. Oxygen, simply on contact with a fluoride glass melt, converts transition metals, e.g. from Fe(II) to Fe(III), from one stable state to another and thereby reduces loss at transmission wavelengths in optical fiber, e.g. the loss at 2.7 .mu.m attributable to Fe(II).

Growing community of inventors

Suffolk, United Kingdom

John R Williams