Temperature Robust Refractive Index Sensor Based on a Photonic Crystal Fiber Interferometer

We present a simple photonic crystal fiber (PCF)-based reflection type interferometer insensitive to temperature for refractive-index measurement. By simply collapsing the airholes at a middle point and forming a reflector at the end of a PCF, the interferometer could be implemented. The PCF sensor showed a low thermal sensitivity even without any compensation process. The feasibility as a refractive-index sensor is demonstrated by presenting the spectral response to liquids having various refractive indexes and to temperature. The implemented sensor showed a good sensitivity of 850 nm/RUI (refractive unit index).