Abstract

In this article, a novel Bayes-Adam-based multiple-input multiple-output (MIMO) equalizer was proposed and experimentally demonstrated for an orbital angular momentum (OAM) mode-division multiplexed (MDM) optical fiber communication system. In general, MIMO equalization is required to compensate the crosstalk of the random intra-group mode coupling in the OAM mode. However, due to the time-varying characteristics of the OAM-MDM transmission, it is a long-standing challenge for MIMO equalization to achieve the high accuracy and fast convergence. In this work, a Bayes-Adam MIMO equalizer based on a penalty term and the Bayesian principle is developed for MDM transmission using eight OAM modes over a 20 km ring-core fiber, which smooths the cost function to achieve global optimization with fast convergence and high accuracy. Experiments show that the proposed adaptive Bayes-Adam MIMO equalizer outperforms two other conventional equalizers in terms of convergence speed and accuracy. The proposed approach achieved fast convergence with only 3,000 iterations for the <+4, left> OAM mode at an OSNR of 22 dB, which is much faster than that of Adam MIMO equalizer (11000 iterations) and SGD MIMO equalizer (16000 iterations). Furthermore, compared with a conventional Adam MIMO equalizer, the proposed scheme gains the OSNR improvement of 4 dB and 3 dB for OAM mode of l = <−4, right> and l = <−5, left> at the hard-decision forward error correction (HD-FEC) threshold, respectively, indicating its strong potential for OAM-MDM transmission.

Scalable mode division multiplexed transmission over a 10-km ring-core fiber using high-order orbital angular momentum modes

Guoxuan Zhu, Ziyang Hu, Xiong Wu, Cheng Du, Wenyong Luo, Yujie Chen, Xinlun Cai, Jie Liu, Jiangbo Zhu, and Siyuan Yu
Opt. Express 26(2) 594-604 (2018)

Mode-division multiplexed transmission of wavelength-division multiplexing signals over a 100-km single-span orbital angular momentum fiber

Junwei Zhang, Junyi Liu, Lei Shen, Lei Zhang, Jie Luo, Jie Liu, and Siyuan Yu
Photon. Res. 8(7) 1236-1242 (2020)

Crosstalk mitigation in a free-space orbital angular momentum multiplexed communication link using 4×4 MIMO equalization

Hao Huang, Yinwen Cao, Guodong Xie, Yongxiong Ren, Yan Yan, Changjing Bao, Nisar Ahmed, Mark A. Neifeld, Samuel J. Dolinar, and Alan E. Willner
Opt. Lett. 39(15) 4360-4363 (2014)

Directly using 8.8-km conventional multi-mode fiber for 6-mode orbital angular momentum multiplexing transmission

Andong Wang, Long Zhu, Lulu Wang, Jianzhou Ai, Shi Chen, and Jian Wang
Opt. Express 26(8) 10038-10047 (2018)

Orbital angular momentum mode multiplexed transmission in heterogeneous few-mode and multi-mode fiber network

Long Zhu, Andong Wang, Shi Chen, Jun Liu, and Jian Wang
Opt. Lett. 43(8) 1894-1897 (2018)