Optical fiber with reduced attenuation due to reduced absorption contribution

A method of making an alkali doped silica core optical fiber comprising:

• determining one or more portions with increased extrinsic absorption in a first optical fiber preform as compared to a baseline of pure silica fiber that is free of any impurities or defects;
• determining one or more production steps, in a production process of the first optical fiber preform, that contribute to the one or more portions with increased extrinsic absorption in the first optical fiber preform;
• treating one or more portions in a second optical fiber preform made from the same production process as the first optical fiber preform;
• and
• drawing the second optical fiber preform into an optical fiber,
• wherein the optical fiber has a total attenuation at 1550 nm of about 0.155 dB/km or less such that extrinsic absorption in the optical fiber contributes to 0.004 dB/km or less of the total attenuation.