Graphene-based optical fiber ammonia gas sensor

To precisely monitor and forecast harmful gases in the air, a high-performance fiber gas sensor based on graphene nanometer-functional materials is proposed and experimentally demonstrated. The sensing area of the proposed sensor was a graphene-wrapped fiber which was cascaded between a down-taper and an up-taper. The graphene wrapping on the subuliform fiber sensing area substantially increased the evanescent field which transmits along the surface of fiber and will have a significant sensitization effect on the gas sensing. At the same time, the gas molecules adsorbed by graphene lead to changes of the effective refractive index of the composite waveguide, which causes corresponding wavelength drift and attenuation. By detecting the change of the output optical signal, the concentration of gas molecules was detected. Based on this principle, the sensor realized a gas sensitivity of 0.015 nm/ppm. The research shows that the sensing structure has the advantages of small volume, good mechanical strength, excellent spectral quality, and high sensitivity.