SDM transmission of orbital angular momentum mode channels over a multi‐ring‐core fibre
Jingxing Zhang, Zhongzheng Lin, Jie Liu, Jie Liu, Junyi Liu, Junyi Liu, Zhenrui Lin, Shuqi Mo, Shuqing Lin, Lei Shen, Lei Zhang, Yujie Chen, Xiaobo Lan, Siyuan Yu
Abstract
Abstract Spatial division multiplexed optical transmission over a multi‐ring‐core orbital angular momentum (OAM) fibre is reported for the first time. The seven cores in the fibre each supports OAM modes belonging to mode groups (MGs) of topological charge | l | = 0–4. The MGs of | l | = 1–4 each contains four near‐degenerate OAM modes that carry the combinations of opposite orbital and spin angular momenta. The weak coupling between these higher‐order MGs as well as between the cores enables the simultaneous transmission of 56 OAM mode channels (two MGs per core of the topological charges | l | = 2 and 3) over the 60‐km span, while only requiring modular 4 × 4 multi‐input multi‐output (MIMO) signal processing to equalize the mixing among the four mode channels in each MG that are strongly coupled – a feature that also minimizes the number of filter taps. The mode channels are launched using seven‐core single‐mode fibre fan‐in devices, with the light in all seven cores converted into OAM modes via specially designed plates that carry seven off‐axis‐compensated phase masks matching the hexagonal configuration of the multi‐core fibres. Each mode channel carries 10 WDM wavelengths, equivalently aggregating to a capacity of 31.4 Tbit/s (net 25.1 Tb/s) and a spectral efficiency (SE) of 62.7 bit/s/Hz (net 50.2 bit/s/Hz) with 28‐GBaud QPSK modulation per data channel.