Design of 18-mode hole-assisted elliptical-core polarization-maintaining few-mode fiber

We present a novel hole-assisted elliptical-core polarization-maintaining few-mode fiber (EC-PM-FMF) composed of three layers of air holes. The proposed fiber breaks degeneracy of modes by introducing geometry asymmetry. Through optimizing the parameters, the designed fiber could support 18 separate polarization-maintaining modes with the minimum effective refractive index difference ( Δ n e f f ) between adjacent modes larger than 1.21 × 10 −4 over the whole C + L band. Moreover, the designed fiber exhibits good mode and propagation properties including large effective mode area, low nonlinear coefficient, small and flat chromatic dispersion , low confinement loss and bending loss. Thus, the fiber can be used in mode division multiplexing (MDM) system without multi-input multi-output (MIMO) digital signal processing (DSP) technology to improve channel utilization. • A novel hole-assisted elliptical-core polarization-maintaining few-mode fiber (EC-PM-FMF) is proposed. • The degeneracy between modes is broken by elliptical core and three layers of air holes arranged in an elliptical shape. • The fiber supports 18 separate modes with Δ n e f f between modes beyond 1.21 ×10 -4 over the whole C + L band. • The EC-PM-FMF exhibits good mode and propagation properties.