Space-division multiplexing (SDM), as a main candidate for future ultra-high capacity fibre-optic communications, needs to address limitations to its scalability imposed by computation-intensive multi-input multi-output (MIMO) digital signal processing (DSP) required to eliminate the crosstalk caused by optical coupling between multiplexed spatial channels. By exploiting the unique propagation characteristics of orbital angular momentum (OAM) modes in ring core fibres (RCFs), a system that combines SDM and C + L band dense wavelength-division multiplexing (DWDM) in a 34 km 7-core RCF is demonstrated to transport a total of 24960 channels with a raw (net) capacity of 1.223 (1.02) Peta-bit s⁻¹ (Pbps) and a spectral efficiency of 156.8 (130.7) bit s⁻¹ Hz⁻¹. Remarkably for such a high channel count, the system only uses fixed-size 4 × 4 MIMO DSP modules with no more than 25 time-domain taps. Such ultra-low MIMO complexity is enabled by the simultaneous weak coupling among fibre cores and amongst non-degenerate OAM mode groups within each core that have a fixed number of 4 modes. These results take the capacity of OAM-based fibre-optic communications links over the 1 Pbps milestone for the first time. They also simultaneously represent the lowest MIMO complexity and the 2nd smallest fibre cladding diameter amongst reported few-mode multicore-fibre (FM-MCF) SDM systems of >1 Pbps capacity. We believe these results represent a major step forward in SDM transmission, as they manifest the significant potentials for further up-scaling the capacity per optical fibre whilst keeping MIMO processing to an ultra-low complexity level and in a modularly expandable fashion.

空分复用 (SDM) 作为未来超大容量光纤通信的主要候选者，需要解决计算密集型多输入多输出 (MIMO) 数字信号处理 (DSP) 对其可扩展性的限制需要消除由多路复用空间通道之间的光耦合引起的串扰。通过利用环芯光纤 (RCF) 中轨道角动量 (OAM) 模式的独特传播特性，展示了在 34 km 7 芯 RCF 中结合 SDM 和 C + L 波段密集波分复用 (DWDM) 的系统传输总共 24960 个通道，原始（净）容量为 1.223 (1.02) Peta-bit s ^-1 (Pbps)，频谱效率为 156.8 (130.7) bit s ^-1 Hz ^-1. 值得注意的是，对于如此高的通道数，该系统仅使用固定大小的 4 × 4 MIMO DSP 模块，时域抽头不超过 25 个。这种超低 MIMO 复杂性是通过光纤纤芯之间以及每个纤芯内具有固定数量的 4 个模式的非退化 OAM 模式组之间的同时弱耦合来实现的。这些结果首次使基于 OAM 的光纤通信链路容量超过 1 Pbps 里程碑。在报告的容量大于 1 Pbps 的少模多芯光纤 (FM-MCF) SDM 系统中，它们同时代表了最低的 MIMO 复杂性和第二小的光纤包层直径。我们相信这些结果代表了 SDM 传输的重要一步，