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 (delta n(eff)) between adjacent modes larger than 1.21 x 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.