Patent ID: 11891331
Assignee: CORNING INCORPORATED
Field: Other special machines (Mechanical engineering)
Classification: CPC C | IPC C

Claim 13:
14. A method of doping a glass preform with nitrogen, comprising:
disposing a glass preform having a first end and a second end in a furnace assembly, wherein the glass preform includes an open channel extending from the first end at least partially through a body of the glass preform toward the second end;
supplying a nitridizing gas to the open channel of the glass preform through a gas supply pathway having an outlet aligned with an inlet to the open channel, wherein the nitridizing gas comprises gaseous NH3;
heating the glass preform to a first temperature in the presence of the nitridizing gas to form a nitrogen-doped glass preform; and
wherein a residence time of the nitridizing gas is <3.0 seconds, and wherein the residence time is defined by formula (III):

Vt/f  (III)

where Vt is an interior volume of the gas supply pathway between a position at which a temperature of the nitridizing gas is >500° C. and an end of the open channel, and where f is the volumetric flow rate of the nitridizing gas in the gas supply pathway.