Design of a circular photonic crystal fiber with square air-holes for orbital angular momentum modes transmission

Abstract

A new circular photonic crystal fiber (C-PCF) with square air -holes in the cladding is proposed, which can support much more orbital angular momentum (OAM) modes. To optimize the design, the dependence of the number of OAM modes on fiber structure parameters is investigated. The simulation results show that the designed C-PCF can support 46 OAM modes stably over 800 nm bandwidth from 1.2 μm to 2.0 μm. Furthermore, the proposed C-PCF exhibits excellent fiber features, such as large effective index differences (˃10−4) without doping, low confinement loss (lower than 10−9 dB/m), relatively flat dispersion and small nonlinear coefficient (less than 2.58 km−1 W−1) for all eigenmodes. The proposed C-PCF could be a well-promising OAM fiber for mode division multiplexing(MDM) in high capacity fiber communication systems.