Modeling the Response of a Long-Period Fiber Grating to Ambient Refractive Index Change in Chemical Sensing Applications

The transmittance spectra of a long-period fiber grating element immersed in different mixtures of water and dimethyl sulfoxide were recorded. The obtained data were compared with a theoretical model based on linearly polarized modes treated with a coupled-mode approach. Excellent agreement between the measurements and theoretical results was found over a wide wavelength range.