Hollow Ring-Core Photonic Crystal Fiber With &gt;500 OAM Modes Over 360-nm Communications Bandwidth

Yingning Wang,Zhongqi Pan,Hao Huang,Zhi Wang,Baiwei Mao,Changjing Bao,Yuxi Fang,Yang Yue,Yao Lu,Yan-Ge Liu,Yongxiong Ren,Wenpu Geng

doi:10.1109/access.2021.3076490

Abstract

We propose and design a hollow As2S3 ring-core photonic crystal fiber (PCF) with 514 radially fundamental orbital angular momentum (OAM) modes over 360 nm communications bandwidth across all the O, E, S, C, and L bands. The designed PCF with 40 $\mu \text{m}$ -radius air core and 150 nm-width As2S3 ring can support eigenmodes up to HE130,1 and EH128,1. The numerical analysis shows that the designed ring PCF has large effective refractive index contrast, and can transmit up to 874 OAM modes near 1.55 $\mu \text{m}$ . Simulation results show that in the C and L bands, the PCF with a hollow-core radius of 40 $\mu \text{m}$ and a ring width of 0.15 $\mu \text{m}$ can retain an $2.5\times 10 ^{-3}$ effective refractive index difference between the two highest order OAM modes, which achieves effective mode separation, thereby achieving stable OAM mode transmission. The $n_{eff}$ difference between the even and odd fiber eigenmodes and the intra-mode walk-off are also carefully studied under different bending radii. The results show that higher-order OAM modes has better tolerance to the fiber bending, compared with the lower-order modes. The fiber has the potential to support ultra-high capacity OAM mode division multiplexing in the optical fiber communication systems.

Highlights

Over the past several decades, the optical communication industry has been developing rapidly
Zhang et al proposed a new type of circular photonic crystal fiber (CPCF), which can support up to 110 orbital angular momentum (OAM) modes in the C and L bands [27]
We propose and design an air-core thin-ring As2S3 PCF to support hundreds of OAM modes, which is systematically modeled and numerically studied by the finite element method (FEM)

Summary

INTRODUCTION

Over the past several decades, the optical communication industry has been developing rapidly. Orbital angular momentum (OAM), which is a compelling candidate for a modal basis of SDM, has attracted extensive attention [5]–[7] It could potentially overcome the problem of insufficient capacity in the current optical fiber communications infrastructures [8]. Zhang et al proposed a new type of circular photonic crystal fiber (CPCF), which can support up to 110 orbital angular momentum (OAM) modes in the C and L bands [27]. To show the robustness of the designed fiber, we calculate the effective refractive index difference between the even and odd fiber eigenmodes when the fiber suffers bending and find that the high-order OAM modes feature satisfying capability of bending tolerance This designed fiber can be potentially used for the OAM-WDM optical communication system to dramatically increase the transmission capacity

PROPOSED PCF STRUCTURE

CONCLUSION