Methods and apparatus for forming optical fiber

An apparatus for manufacturing an optical fiber, comprising:

• a draw furnace having a passage containing
• an optical fiber preform from which the optical fiber can be drawn, and
• a forming gas having a first thermal conductivity coefficient;
• and a heat aging treatment device positioned downstream of the draw furnace, the treatment device including
• a treatment tube, and
• a treatment gas distributor fluidly connected thereto, the gas distributor having at least two axially spaced supply ports connected to the tube at at least two axially spaced locations enabling supply of treatment gas to the tube at the at least two axially spaced locations.

An apparatus for forming and treating an optical fiber, comprising:

• a draw furnace including an exit wall and adapted to form the optical fiber such that the optical fiber exits the draw furnace at the exit wall, the draw furnace containing a first gas also exiting at the exit wall;
• a passive muffle disposed adjacent the draw furnace having first and second ends and defining a passage, the passage containing a second gas having a lower thermal conductivity than the first gas wherein the first gas enters the passage at the first end and the first and second gases mix in the passive muffle and exit at the second end;
• and
• wherein the passive muffle is joined to the exit wall at the first end such that ambient air cannot enter the draw furnace or the passive muffle at the joinder therebetween.