Optical fiber humidity sensor based on surface plasmon resonance in the infra-red region

Here, the fabrication and characterization of a novel optical fiber humidity sensor based on surface plasmon resonance (SPR) in the infra-red region is presented. Firstly, an indium tin oxide (ITO) coating is deposited onto a 200 μm core diameter optical fiber causing the shift of the SPR wavelength to the infra-red region. Then, the LbL method is used to deposit a polymeric coating onto the ITO layer. The variations in the external humidity originated changes in the thickness and refractive index of the polymeric coating and hence in the resonance.