Nanophotonics (Nov 2021)

SDM transmission of orbital angular momentum mode channels over a multi-ring-core fibre

  • Zhang Jingxing,
  • Lin Zhongzheng,
  • Liu Jie,
  • Liu Junyi,
  • Lin Zhenrui,
  • Mo Shuqi,
  • Lin Shuqing,
  • Shen Lei,
  • Zhang Lei,
  • Chen Yujie,
  • Lan Xiaobo,
  • Yu Siyuan

DOI
https://doi.org/10.1515/nanoph-2021-0471
Journal volume & issue
Vol. 11, no. 4
pp. 873 – 884

Abstract

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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.

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