Temperature Sensor Based on an Asymmetric Two-Hole Fiber Using a Sagnac Interferometer

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