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In this paper we report the experimental results of a fiber optic refractometer based in multimodal interference effects (MMI) using an Indium Tin Oxide (ITO) coating. The MMI sensor is able to detect different liquid concentrations of glycerin and other substances. In addition, the use of ITO coating, deposited by the sputtering technique, allows a significant increment in the device sensitivity. In specific, we obtained a sensitivity around 297.12 nm/RIU for 18nm ITO coating thickness Keywords-fiber optic sensor, multimode interference, refractometer, ITO coating.

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We report in this paper a temperature sensor based on an asymmetric two-hole fiber (ATHF) using a Sagnac interferometer (SI) configuration. The operation principle is based on the birefringence change induced by the temperature difference between the air holes and the silica fiber. As a result, the transmitted spectrum of the SI exhibits a sinusoidal profile which is shifted when the temperature is increased. A linear wavelength shift as a function of temperature is observed, and a sensitivity of 2.22 nm/°C was achieved using a 2 m long asymmetric THF, which is in the same order as those previously reported using similar microstructured fibers. The advantage of this system is a linear response, the use of a microstructured fiber with a simpler transverse geometry, and the use of bigger holes which can facilitate the insertion of several materials and improve the sensitivity of the sensor for different applications.