Relative humidity sensor of S fiber taper based on graphene oxide film

The S fiber taper (SFT) sensor based on graphene oxide (GO) film is proposed for measuring relative humidity (RH). The SFT is obtained by melting a single mode fiber (SMF) through a fusion splicer and the film is coated by an in-situ layer-by-layer (i-LbL) technique. Different tapered waist diameters and different cycle coating times of GO film are discussed. According to the experimental results, the sensor has the highest humidity sensitivity when the tapered waist diameter is 27 μm and the GO film is cyclically coated 12 times. Its maximum intensity sensitivity is -0.361 dB/%RH and the maximum wavelength sensitivity is 365 pm/%RH in the range of 84%RH to 95%RH. The temperature fluctuations at room-temperature have less than 2%RH impact on humidity testing. The sensor is compact, easy to manufacture, fast in recovery and excellent in performance.