Thermal characteristics of phase shift in jacketed optical fibers

Frequency and pulse methods are applied to measure thermal characteristics of phase shift in bare and jacketed optical fibers. The thermal coefficient of phase shift in bare fibers is found to be 7 × 10−6/deg, which is in good agreement with the value predicted theoretically. It is also found that the coefficient is increased by four times after nylon jacketing due to the increase of the coefficient of linear expansion.