Optical fiber and method of producing an optical fiber

A method of manufacturing an optical fiber package by carrying out one or more chemical vapour deposition reactions in a substrate tube, with the optical fiber core exhibiting a low sensitivity to the hydrogen induced attenuation losses over operating and transmitting wavelengths in the range from 1000 nm to 1600 nm, the method comprising the steps of:

• i) providing an optical fiber substrate preform tube with glass forming precursors;
• ii) supplying a stoichiometric excess amount of oxygen to the tube;
• iii) generating a reaction in the substrate tube to form an amorphous glass layer on the interior of the tube;
• iv) depositing a layer of unsintered soot comprising SiO2 within the tube;
• v) supplying a Cl2 atmosphere;
• vi) sintering the glass layer in the tube;
• vii) collapsing the optical preform tube of step (vi) in a Cl2 atmosphere so as to form a preform;
• and
• viii) drawing an optical fiber from the preform formed in step vii) with the application of heat and tension of weight in the range 30 to 70 g and providing an optical fiber coating.