Apparatus and method for drawing glass fibers

An apparatus for drawing a fluoride glass fiber from a fluoride glassrod preform having a longitudinal axis which comprises:

• an insulated vessel having a top wall, a bottom wall, side walls connected to define a chamber therein for heating said preform, an entrance opening in said top wall through which said preform enters and an exit opening in said bottom wall through which said glass fiber exits;
• means within said chamber for heating a zone therein to a uniform temperature of such magnitude that said preform softens and flows when in said zone, said zone being so narrow that said fiber can be drawn from said preform without appreciable crystallization;
• means in communication with said heating zone and said heating means for controlling the temperature within said zone to ±0.5° C.;
• means connected to said insulated vessel at said entrance opening thereof for preventing convection currents around said preform but allowing said preform to move through said means and into said heating zone;
• means for moving said preform along its longitudinal axis into said heating zone at a predetermined speed;
• means for passing a stream of reactive gas around said preform and fiber so as to flush the surfaces of said preform and fiber with said reactive gas, thereby removing contaminants therefrom by chemical reaction and elimination of air;
• and
• means for pulling said fiber from said preform.