Zhang Jingxing, Lin Zhongzheng, Liu Jie, Liu Junyi, Lin Zhenrui, Mo Shuqi, Lin Shuqing, Shen Lei, Zhang Lei, Chen Yujie, Lan Xiaobo, Yu Siyuan
State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510006, China.
State Key Laboratory of Optical Fiber and Cable Manufacture Technology, Yangtze Optical Fiber and Cable Joint Stock Limited Company, Wuhan 430073, China.
Nanophotonics. 2021 Nov 19;11(4):873-884. doi: 10.1515/nanoph-2021-0471. eCollection 2022 Jan.
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 || = 0-4. The MGs of || = 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 || = 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.
首次报道了在多环芯轨道角动量（OAM）光纤上的空间分割复用光传输。光纤中的七个芯各自支持属于拓扑电荷|| = 0 - 4的模式组（MGs）的OAM模式。|| = 1 - 4的MGs各自包含四个近简并OAM模式，这些模式携带相反的轨道角动量和自旋角动量的组合。这些高阶MGs之间以及芯之间的弱耦合使得能够在60公里的跨度上同时传输56个OAM模式通道（拓扑电荷|| = 2和3时每个芯两个MGs），而只需要模块化4×4多输入多输出（MIMO）信号处理来均衡每个MG中强烈耦合的四个模式通道之间的混合 - 这一特性也使滤波器抽头的数量最小化。模式通道使用七芯单模光纤扇入装置发射，所有七个芯中的光通过专门设计的板转换为OAM模式，这些板带有与多芯光纤的六边形配置匹配的七个离轴补偿相位掩模。每个模式通道携带10个波分复用（WDM）波长，等效地聚合到31.4 Tbit/s（净25.1 Tb/s）的容量和62.7 bit/s/Hz（净50.2 bit/s/Hz）的光谱效率（SE），每个数据通道采用28 - 波特四相相移键控（QPSK）调制。
