ABSTRACT
Chemical sensing with optical fibers allows fast and real-time detection, with the possibility of low-cost equipment and procedures. A transduction mechanism is necessary in chemical sensing, responsible for the conversion of the desired quantity to be detected in a variation that can be measured, namely optical properties. Intrinsic fiber optic chemical sensors have been reported in the scientific literature since 1946. Plastic optical fiber (POF) chemical sensors can be considered extrinsic or intrinsic, depending on if the POF is only the waveguide where the light travels or if the POF is actively interacting with the external medium/selective layer acting also as a transducer and sensing element. The interaction of light with matter and chemical species is dependent on their characteristics and also on the wavelength of the incident light. These light–matter characteristic interactions allow the so-called spectroscopic sensing techniques: reflection, refraction, scattering, diffraction, absorption, emission, etc.
