Abstract

Modal multiplexing can greatly increase fiber capacity, but often at the cost of high digital processing with multiple-input multiple-output (MIMO) algorithms. The use of orbital angular momentum (OAM) for multiplexing can support MIMO-free reception, but it always operates in an interferencelimited regime. Many previous MIMO-free demonstrations for OAM used a type of optical MIMO that is impractical for deployed systems. We compare the performance of MIMO-free and standard electronic 2 × 2 MIMO in a demonstration with no recourse to optical MIMO. We show that the receiver complexity of these two reception strategies is very similar in hardware and signal processing. We explore commercial coherent receivers with 2 × 2 MIMO, hence this solution for OAM demultiplexing can be deployed effectively with current technology. The 2 × 2 MIMO reception enhances the total bit rate and is more compatible with wavelength division multiplexing (WDM) as it equalizes performance across the C-band. At 1.3 km transmission, the net bit rate spans 426–450 Gb/s across wavelengths with 2 × 2 MIMO, while variability is high for MIMO-free reception, spanning 200–418 Gb/s.

Free-space optical communications using orbital-angular-momentum multiplexing combined with MIMO-based spatial multiplexing

Yongxiong Ren, Zhe Wang, Guodong Xie, Long Li, Yinwen Cao, Cong Liu, Peicheng Liao, Yan Yan, Nisar Ahmed, Zhe Zhao, Asher Willner, Nima Ashrafi, Solyman Ashrafi, Roger D. Linquist, Robert Bock, Moshe Tur, Andreas F. Molisch, and Alan E. Willner
Opt. Lett. 40(18) 4210-4213 (2015)

Turbulence-resistant high-capacity free-space optical communications using OAM mode group multiplexing

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1120-channel OAM-MDM-WDM transmission over a 100-km single-span ring-core fiber using low-complexity 4×4 MIMO equalization

Junyi Liu, Zhenrui Lin, He Zhu, Lei Shen, Shuqi Mo, Zhenhua Li, Jingxing Zhang, Junwei Zhang, Xiaobo Lan, Jie Liu, and Siyuan Yu
Opt. Express 30(11) 18199-18207 (2022)

Atmospheric turbulence mitigation in an OAM-based MIMO free-space optical link using spatial diversity combined with MIMO equalization

Yongxiong Ren, Zhe Wang, Guodong Xie, Long Li, Asher J. Willner, Yinwen Cao, Zhe Zhao, Yan Yan, Nisar Ahmed, Nima Ashrafi, Solyman Ashrafi, Robert Bock, Moshe Tur, and Alan E. Willner
Opt. Lett. 41(11) 2406-2409 (2016)

OAM mode multiplexing in weakly guiding ring-core fiber with simplified MIMO-DSP

Shi Chen, Shuhui Li, Liang Fang, Andong Wang, and Jian Wang
Opt. Express 27(26) 38049-38060 (2019)