All-glass single-mode microstructured optical fibres with a large-diameter core and low bending losses

All-glass microstructured optical fibres (MOFs) with a core 20 μm in diameter and two rings of circular fluorine-doped silica glass elements with a reduced refractive index, different diameters, and different distances between them are theoretically studied. The properties of these MOFs are numerically analysed using the finite element method. The leakage losses for the fundamental and higherorder modes in the spectral range 0.75–1.65 μm are calculated for straight and bent MOFs. It is shown that the considered MOF design allows single-mode operation in the range 0.98–1.26 μm at a bending radius of down to 0.08 m, the leakage losses for the bent MOF at a wavelength of 1.05 μm being 0.046 dB m^-1.