High sensitivity evanescent-field gas sensor based on modified photonic crystal fiber for gas condensate and air pollution monitoring

Flammable and/or toxic gas sensors can be used as safety measuring in gas production facilities, especially in oil rigs. The gas sensors detect gas leaks capable of causing fire, explosion, and toxic exposure. Here we proposed an index-guiding photonic crystal fiber for gas sensing that have a broad spectral transmission band and so is capable to detect more gas condensate components. The dependence of relative sensitivity and confinement loss on the fiber parameters is numerically investigated by finite element method (FEM). Introducing a hollow high index ring with an air hole in the center of fiber simultaneously enhances the relative sensitivity and achieves low confinement loss. In addition, we prove that increasing the diameter of holes located in the inner rings, improve the relative sensitivity and increasing the ring diameter holes located in the outer rings, greatly reduces the confinement loss. Placing hexagonal holes instead of circular holes in the innermost ring, the relative sensitivity is effectively enhanced. The relative sensitivity at wavelength of lambda = 1.33 mu m that is in the Methane absorption line is enhanced to value of 13.23%. The confinement loss is also improved to 3.77 x 10(-6). (C) 2013 Elsevier GmbH. All rights reserved.