Humidity and temperature sensor based on a Mach–Zehnder interferometer with a pokal taper and peanut taper

An optical fiber sensor for simultaneous measurement of humidity and temperature is proposed and investigated. The sensor is composed of a pokal taper and a peanut taper spliced at both ends of a single-mode fiber, respectively. In the experiment, the variations of the dip wavelength are used to measure the parameter sensing characteristics. The sensing area is coated with a concentration of 1 mg/ml graphene dispersion by using the optical driven deposition method. Experimental results show that the sensor has a good linear relationship with temperature and humidity. When the humidity measurement range is 30%RH∼70%RH, the sensitivities are 0.059 nm/%RH and 0.133 nm/%RH, respectively. When the temperature measurement range is 0∘C∼40∘C, the sensitivities are 0.254 nm/°C and 0.269 nm/°C, respectively. This sensor has the advantages of small size, low cost, and high response.