Agarose optical fibre humidity sensor based on electromagnetic resonance in the infra‐red region

A new optical fibre humidity sensor based on electromagnetic resonances (EMR) is presented in this work. An ITO layer deposited onto a 200 µm core fibre has been used as EMR supporting coating. The resultant device works as a refractometer whose EMR absorption peak shifts when the refractive index of the surrounding medium varies. An agarose layer, whose refractive index changes when it is subjected to relative humidity (RH) variations, has been deposited onto the ITO layer. This way, the new device shows a good sensitivity to RH variations, with a dynamical range of 45 nm between 20 and 80% RH. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)