Optimization of fiber-optic evanescent wave spectroscopy: A Monte Carlo approach

The absorbance of the evanescent waves of infrared radiation transmitted through an optical fiber depends on the geometry of the fiber in addition to the wavelength of the electromagnetic radiation. The signal can thus be enhanced by flattening the midsection of the fiber. While the dependence of the absorbance on the thickness of the midsection has already been studied and experimented upon, we demonstrate that similar results are obtained using Monte Carlo methods based simply on geometrical optics, given the dimensions of the fiber and the power distribution of the fired rays. The optimization can be extended to fibers with more complex geometries of the sensor.