Absolute calibration of a distributed temperature sensor of optical path fluctuations

A Jamin-type interferometer was used in absolute calibration of a method for the determination of optical path fluctuations from measured temperature-induced fluctuations of the resistance of a thin tungsten wire. The calibration of the method corresponded to variations in the refractive index with temperature in accordance with the law Δ n = –10^–6Δ T(°C), representing dry air at constant pressure. Measurements were made of atmospheric fluctuations of the refractive index under laboratory conditions.