Simulations were performed in order to investigate whether the stationary phase point method can be used to estimate the dominance of higher-order dispersion of the optical element under study. Moreover, we explore the reasons behind the evolutions of the minimum loss contrasts for the HE11 and TE01 modes between both types of HC-BFs with the core diameter, by quasi-quantificationally analyzing the influences of reflection characteristics of the transverse electric (TE) and transverse magnetic (TM) waves on the confinement loss. In contrast, the changes of cladding structures have very limited influence on the confinement loss of the TE01 mode in both the large-core and small-core HC-BFs. The differences in minimum confinement losses of the HE11 mode between both types of HC-BFs decrease with decreased core diameters. The confinement loss of the fundamental HE11 mode in the TPC-based HC-BF is much lower than that in the BPC-based HC-BF, which is essentially attributed to the stronger modal field confinement by the TPC. The bandwidth contrast for a given guided mode in large-core HC-BFs is different from that in small-core HC-BFs. The contrasts in bandwidths for the guided modes between both types of HC-BFs strongly depend on their distinct frequency cutoff characteristics. The influences of structural changes from the binary periodic cladding (BPC) to the ternary periodic cladding (TPC) on the dispersion relations, confinement losses, and modal field distributions of the lowest five guided modes are thoroughly discussed under different core diameters. We comparatively investigate the modal properties of guided modes in hollow core Bragg fibers (HC-BFs) with the binary and ternary photonic bandgap claddings by using a full-vector finite element method. All of these factors must be taken into consideration during the design of dispersion tailored fibers for different applications. Furthermore, a rapid variation in the group delay versus wavelength function due to mode-crossing events (in hollow core photonic bandgap fibers for instance) or resonances originating from slightly coupled cavities, surface or leaking modes in index guiding, photonic bandgap, or photonic crystal fibers always results in a rapid change in the mode-field distribution, which seriously affects splicing losses and focusability of the transmitted laser beam. In case of a dispersion tailored Bragg fiber, we found that the stored energy-group delay ratio decreased while the confinement loss increased compared to those of the standard quarterwave Bragg fiber configuration. ![]() The stored energy-group delay ratio typically approaches unity as the confinement loss converges to zero. We show by numerical computations that the group delay of an optical pulse of finite bandwidth transmitted through a piece of a low loss optical fiber of unit length is proportional to the energy stored by the standing wave electromagnetic field. The relationship between transmission group delay and stored energy in optical fibers is discussed.
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