In this paper, an optical fiber sensor is proposed for measurement of the boiling point and boiling range of liquids. Since boiling point and/or boiling range of liquids correlate directly to chemical composition of liquids, the proposed sensor provides opportunity for on-line and in-situ chemical characterization of various liquids. The proposed sensor is manufactured on the tip of a standard optical fiber, and consists of a Fabry-Perot temperature sensor and short section Vanadium doped fiber, which serves as a microheater. The latter is cyclical and rapidly heated by application of high-power fiber-coupled laser diode, while the Fabry-Perot temperature sensor is used to detect appearance of boiling process and to measure the absolute temperature. The proposed sensor is less than 1 mm long and allows for characterizing samples in quantities of 140 nL in as short time as ten seconds. All-silica/all-fiber design of the sensor provides high chemical inertness, dielectric design and possibility for remote operation. Two sensor types are proposed; the first is intended for measurement of very small samples (140nL). This measurement takes only about 10 seconds. The second sensor type is suitable for online monitoring of binary or multicomponent mixtures, and provides accurate boiling range data of a given mixture.
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