Bending effect on fiber optic evanescent absorption sensor for sensitivity enhancement in hetero-core structured fiber optic

摘要

Hetero-core structured fiber optic was applied to evanescent field absorption spectroscopy. The sensing part of the fiber optic was immersed in a dye solution, then the bending was applied to the fiber optic probe, and propagating loss spectra were measured. The effects of refractive index of the dye solution and the degree of the bending to the sensor part were studied. According to increasing of the degree of bending, the peak strength of the spectra of the dye increased. This is because that the increasing of the bending degree changes the angle of incidence in the propagating ray following the evanescent wave is generated effectively, hence the number of the dye molecules that can interact with the evanescent wave increases. As a result, the sensitivity enhancement of the peak strength was performed. In addition, the increase of the refractive index of the dye solution enhanced the peak intensity in the absorption spectra. It has been shown that the sensitivity enhancement of the fiber optic sensor would be performed by physical shape control and physical property of the solution such as refractive index.