Design and characteristics of ellipse-assisted ring-core fiber for space division multiplexing

•Elliptical-assisted ring-core fiber with central low-refractive-index elliptical region.•9 effectively separated spatial modes have uniform Δneff with values greater than 3.14 × 10−4 at 1550 nm.•The level of polarization separation is lower than 3.33 × 10−6.•Good scalability and fabrication error tolerance.•This fiber design could be promising candidates toward high-capacity SDM systems.