An Optical Fiber Fabry–Perot Interferometer Sensor for Simultaneous Measurement of Relative Humidity and Temperature

A simultaneous relative humidity (RH) and temperature sensor based on an optical fiber Fabry-Perot interferometer is proposed and experimentally demonstrated. This sensor is constructed by splicing a short length of photonic crystal fiber (PCF) to single mode fiber and coating an ultrathin polyvinyl alcohol film to the PCFs cleaved surface. The total length of this sensing head is only ~110 μM and the compact size means it can be used flexibly in limited space and harsh environments. Experimental results demonstrate that this sensor can simultaneously measure the ambient RH and temperature by demodulating the power change and wavelength shift of reflection spectrum. Consequently, the advantages of compact size, low cost, high flexibility and stability, fast response, and simultaneous RH and temperature measurement ability means the proposed sensor has an extensive range of potential applications.