All-optical, all-fiber, thermal conductivity sensor for identification and characterization of fluids

This paper presents a miniature, all-optical, thermal conductivity fiber-optic sensor, which can be applied to various fluid composition identification situations. The sensor is composed of a short section of highly absorbing fiber, which is configured as a Fabry-Perot interferometer. A higher power laser diode is used to heat the absorbing fiber periodically, while proper signal integration system issued in order to observe temperature variations of the heated fiber. These variations are further correlated to the surrounding fluid's thermal conductivity. The sensor was applied experimentally to various fluid identification situations, including gas/liquid and liquid-liquid phase detection, identification of different fluids (including liquids and gases), liquids' binary mixtures mass ratio determination, and some common fluid identification applications.