Fiber Optic Hybrid Device for Simultaneous Measurement of Humidity and Temperature

A novel fiber optic hybrid device for simultaneously measuring temperature and relative humidity (RH) is proposed and demonstrated in this paper. The device is composed of a fiber Bragg grating (FBG) and a reflection type photonic crystal fiber interferometer (PCFI) infiltrated with humidity sensitive material Agarose. The Agarose infiltrated PCFI is used to monitor the RH and an in-line FBG is used to monitor the temperature. The temperature is measured by detecting the shift in the Bragg wavelength and the humidity is measured by monitoring the change in the optical power of the reflected spectrum. The sensor shows a temperature sensitivity of 9.8 pm/ $^{\circ}{\rm C}$ and an optical power variation of ${>}{\rm 7}~{\rm dB}$ for an RH change of 75%, with less cross sensitivity.