Loop-Fiber coated with graphene oxide incorporating a FBG to sense humidity and temperature simultaneously

A novel temperature (T) and relative humidity (RH) sensor based on a graphene oxide (GO)-coated Loop-Fiber that incorporates a fiber Bragg grating (FBG) is proposed in this work. The uniform waist area of the tapered area was coated with GO for RH measurement. At the same time, FBG was used to overcome the T cross-sensitivity, thereby making a T and RH sensor. Experimental results show that the structure is sensitive to T and RH, and the sensitivity in the T range of 35 °C to 60 °C and humidity range of 37.7–65.5 %RH is −201.1 pm/°C and −141.7 pm/%RH. Corresponding resolutions are 0.14 %RH and 0.1 °C. FBG is insensitive to RH but sensitive to T and its T sensitivity is 5.2 pm/°C. Many experiments showed the excellent reversibility and repeatability of the sensor. This sensor has the advantages of high sensitivity, simple structure, easy production and low cost. It can also be used for measuring T and RH simultaneously.