Decreased H2 sensitivity in optical fiber

A method of making a treated soot preform which is a precursor of a hydrogen resistant waveguide fiber, comprising the steps of:

• fabricating a soot preform comprising a central core region surrounded by and in contact with a clad region;
• and, after said fabricating step,
• heating said preform in a gaseous environment to a temperature greater than about 800° C. but less than the consolidation temperature thereof and then, after said heating step, adding GeCl4 gas to the gaseous environment and exposing said preform to the gas while maintaining the preform below its consolidation temperature for a time and temperature which is sufficient to treat said preform with the gas so that, when said preform is employed in a fiber draw process for making an optical fiber, the resultant fiber exhibits less than 0.05 dB/km increased attenuation at 1530 nm after exposure to a 1% hydrogen atmosphere at a pressure of 1 atm for 6 days.