Heterodyne interferometric measurement of the thermo-optic coefficient of single mode fiber

The thermo-optic coefficient of a single mode fiber is determined by a hete rodyne interferometric technique. The heterodyne beat signal, resulting fro m the beating of the carrier and two side-band frequencies, is related to t he phase shift difference between the carrier and the side-band waves in a fiber Fabry-Perot interferometer. This phase shift difference is determined with a phase sensitive detection technique and is found to be temperature dependent. From the temperature dependence, the thermo-optic coefficient of the single mode fiber is determined to be 9.2 x 10(-6) C-1. The experiment al result agrees well with a theoretical simulation using the temperature d ependent Sellmeier equation for fused silica.