Short-Time Optical Fiber Thermal Conductivity Sensor

Abstract

Thermal conductivities of liquids have been determined by using a variation of the transient hot-wire technique. A short segment of one arm of a fiber-optic Mach-Zehnder interferometer is coated with a thin layer of gold. This gold layer is heated resistively with a 1 msec current pulse producing a temperature change of only tenths of a degree. The magnitude of this temperature change (determined by the phase change in the interferometer) can be used to calculate the thermal conductivity of the medium in which the fiber is immersed. The conventional transient hot-wire thermal conductivity technique employs a much larger temperature rise and requires numerous correction terms. Results obtained in aqueous ethylene glycol solutions are reported.