Noncontact measurement of optical fiber draw tension

A simple technique for measuring the tension on an optical fiber during the draw process without contacting the fiber surface is reported. It is based on detecting the resonant vibrational frequency of the fiber during draw using the position output of the fiber diameter monitor and requires no specialized circuitry. The tension, determined from the fundamental resonant frequency of the length of fiber between the neckdown region in the furnace and the coating cup, is accurate to within 1% and repeatable to <0.0005 kg