Impact of Transversal Defects on Confinement Loss of an All-Solid 2-D Photonic-Bandgap Fiber

We numerically investigate the impact of transversal defects on the minimum confinement loss value in the case of a solid-core photonic-bandgap fiber with parabolic germanium-doped inclusions. We show that a standard deviation of only 5% of either the diameter, the refractive-index contrast, or the position of the high-index inclusions could double the minimal value-as a function of frequency-of losses. Moreover, we demonstrate that, in our case, accurately controlling the position of the doped inclusions along the first ring around the core is more important than having an accurate control on their diameter and index contrast. Oddly enough, we also point out that the defects could lead to a decrease of the minimum loss value. Furthermore, we demonstrate that a structure made of inclusions of two different refractive indices could have lower loss than both structures made of only one of these two types of inclusion.