Surface flaw healing during fiber drawing.

Some types of optical fibers, including the current dispersion- shifted design, must be drawn at relatively low draw temperatures in order to obtain the lowest losses. Any flaws present in the preform will undergo less healing at the lower draw temperatures creating the potential for reduced fiber strengths. However, when preforms are carefully fire polished to eliminate surface flaws, high strengths can be achieved at relatively high draw tensions (low draw temperatures). Also, furnace temperature rather than draw tension determines the amount of flaw healing which takes place during drawing.