Humidity sensor based on power leakage at resonance wavelengths of a hollow core fiber coated with reduced graphene oxide

A novel humidity sensor based on power leakage at resonance wavelength in a reduced graphene oxide coated hollow core fiber is demonstrated. The reduced graphene oxide is deposited on the outer surface of the hollow core fiber, and a Fabry-Perot resonator is formed in the cladding region. The leaky mode of the guided light can be achieved at resonant wavelength of the Fabry-Perot resonator, which results in lossy dip in the transmission spectrum of the hollow core fiber. Due to the tunable refractive index of the reduced graphene oxide, the humidity can be measured by interrogating the transmission intensity of the lossy dip. The experimental results show that the sensitivity of up to 0.22 dB/% RH is achieved. The humidity sensor possesses good repeatability, fast response time, and low temperature cross-sensitivity. The reduced graphene oxide based humidity sensor appears to have potential applications in researches of chemistry, medicine, and biology.