Results of mode and dispersion analysis for silica few-mode hollow-GeO2-doped-ring core microstructured optical fiber

This work presents results of mode analysis and dispersion spectral characteristic computation, performed for recently presented successfully fabricated silica few-mode microstructured optical fiber (MOF) with hollow-GeO₂-doped-ring core (HRC). Here, we utilized manufactured HRC MOF end face photo image to get averaged parameters for input data. Therefore, following simplified model HRC MOF was simulated and researched: it has outer diameter 67 µm; inner diameter of hollow ring-core is 10 µm, wall thickness 4 µm and refractive index difference Δn = 0.030 (percent of GeO2 dopant is about 20.5 mol%); 90 air holes, placed over typical hexagonal geometry in the periphery region with averaged diameter 1.85 µm and pitch 3.9 µm. According to simulation results (mode analysis, performed by rigorous finite element method via commercially available software COMSOL Multiphysics® 6.1), modeled HRC MOF provides two guided LP-modes (fundamental LP₀₁ and the first higher-order LP₁₁) or 4 HE/EH odd and even eigenmodes – HE₁₁/EH₁₁ and HE₂₁/EH₂₁, respectively: therefore, two orbital angular momentum (OAM) modes (OAM₁₁and OAM₂₁) are localized and supported by the researched and simulated HRC MOF design. In this work we present results of spectral characteristics, computed for mode effective refractive indexes as well as for mode group delays and chromatic dispersion parameters, calculated both for eigen and OAM modes.