Agarose coated macro-bend fiber sensor for relative humidity and temperature measurement at 2 μm

We proposed an agarose coated macro-bend fiber (AC-MBF) sensor for relative humidity and temperature measurement at 2 mu m. Stronger resonance dips in the bent fiber sensor can be found at 2 mu m region, which is at the peak of water absorption better for humidity sensing. Experimentally, such an AC-MBF sensor was very sensitive to humidity at 2 mu m region. The highest sensitivity of 0.314 nm/%RH was achieved in the range of 40-95%, which was much higher than the wavelength-modulated sensors at 1.5 mu m reported previously. Meanwhile, the sensor is also very sensitive to temperature. The maximum temperature sensitivity of the macrobend fiber sensor is 5.37 nm/degrees C. Additionally, AC-MBF sensor is with fast response time and recovery time of similar to 300 ms and 600 ms, respectively.