Analysis of characteristics of the sensing elements for the fiber-based evanescent wave spectroscopy in the mid-IR

Characteristics of the sensing element of a fiber sensor for evanescent wave mid-IR spectroscopy have been studied within the electromagnetic theory of fiber waveguides by using the problem of determining the concentration of aqueous acetone solutions as an example. A multimode chalcogenide fiber was used as a sensing element. It has been shown that the selective excitation of the fiber modes may provide the possibility to increase the sensitivity of the fiber sensing element, decrease the minimum detectable concentration of a substance in a solution, and enhance the range of measured solution concentrations.