Draw tower furnace diagnostics applying a sapphire fiber Bragg grating probe

Abstract

Sapphire fiber Bragg gratings (SFBG) were used for temperature diagnosis of a commercial inductive heated furnace of a fiber draw tower. In a fiber preform temperature gradients > 10K/mm were detected. In the temperature range from 1000°C to 1900°C the measured temperature inside the furnace is about 140K below the control temperature detected by a pyrometer on a spot of the heating element. The dependence of applied temperature on the furnace heating power was derived that can allow furnace control without pyrometer and therefore extending operation range below 1000°C. No degradation of SFBG was observed.