In this work, we design and numerically investigate a silica-cladded Germania-doped ring-core fiber (RCF) that supports orbital angular momentum (OAM) modes with all-normal dispersion. By optimizing the structure parameters of the designed RCF, an all-normal and flat dispersion with a total variation of <±30 ps/nm/km over 1035-nm bandwidth from 965 to 2000 nm is realized for the OAM1,1 mode. A 1.3-octave supercontinuum spectrum of the OAM1,1 mode is generated numerically after launching a 40-fs 200-kW chirp-free hyperbolic secant pulse train centered at 1700 nm into a 2-cm long designed fiber with 50 mol% Ge-doped ring-core, covering 1290-nm bandwidth from 885 nm to 2175 nm at −40 dB power level. The coherence of the generated supercontinuum of the OAM1,1 mode depicts nearly perfect property over the whole spectral range. This design can serve as an efficient way to extend the spectral coverage of beams carrying OAM modes in various applications.
