Abstract
The present work is motivated by the current need of increasing the yield of optical fiber drawing by using high draw speeds. For such conditions the preform feed rate through the draw tower furnace can affect the heat transfer to the preform rod and as a consequence the formation of the neckdown. In the present work temperature distributions along the axis of stationary as well as moving graphite and fused silica rods inserted in a fiber optic draw tower furnace was found experimentally. Experimental data clearly showed that the thermal lag increased at higher draw speeds. Implications of this to high speed fiber drawing are highlighted. Measured temperatures were compared with numerically computed temperature distributions in moving rods. Excellent agreement was found between the temperature recorded in moving graphite rod experiments and the computed temperatures which validated the furnace temperature profile found in the previous work. However, for glass rods the computed temperature lag was greater than the measured temperature lag. The difference between computed glass temperatures and those measured using a thermocouple was explained using a simplified modeling taking into account spectrally selective radiation properties of glass.
