Abstract

In this paper, we experimentally demonstrate the mitigation of atmospheric turbulence effects using phase patterns that apply the inverse transmission matrix for pre-compensation in the 200-Gbit/s free-space orbital angular momentum (OAM) multiplexed optical link. In this link, two OAM channels are multiplexed, each carrying a 100-Gbit/s quadrature-phase shift keying (QPSK) signal. In the uni-directional (forward) link, a combination of two OAM modes is generated using a designed phase pattern in each of the two channels. After the two channels are multiplexed, each OAM mode will carry the combination of signals from both channels. Such beams could perform the inverse function of turbulence-induced crosstalk. We explore the link performances including crosstalk and bit error rate (BER) under 6 different turbulence realizations with a Fried parameter of 1-mm. We find the following: (a) the inter-channel crosstalk is reduced by up to 21 dB; (b) the inter-channel crosstalk is below −10 dB for the 6 turbulence realizations when the compensation is applied; (c) a BER below the FEC limit could be realized for the 6 turbulence realizations with an optical signal-to-noise ratio (OSNR) of 16.8 dB for the uni-directional link with the compensation. Moreover, the post-compensation is also investigated for the two 100-Gbit/s OAM-multiplexed backward channels in the bi-directional link. For the backward channels, the phase patterns are used to mitigate turbulence-induced crosstalk at the receiver for backward channels, and the inter-channel crosstalk is reduced by up to 16 dB.

Demonstration of turbulence mitigation in a 200-Gbit/s orbital-angular-momentum multiplexed free-space optical link using simple power measurements for determining the modal crosstalk matrix

Nanzhe Hu, Haoqian Song, Runzhou Zhang, Huibin Zhou, Cong Liu, Xinzhou Su, Hao Song, Kai Pang, Kaiheng Zou, Brittany Lynn, Moshe Tur, and Alan E. Willner
Opt. Lett. 47(14) 3539-3542 (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)

Mitigation for turbulence effects in a 40-Gbit/s orbital-angular-momentum-multiplexed free-space optical link between a ground station and a retro-reflecting UAV using MIMO equalization

Long Li, Runzhou Zhang, Peicheng Liao, Yinwen Cao, Haoqian Song, Yifan Zhao, Jing Du, Zhe Zhao, Cong Liu, Kai Pang, Hao Song, Ahmed Almaiman, Dmitry Starodubov, Brittany Lynn, Robert Bock, Moshe Tur, Andreas F. Molisch, and Alan E. Willner
Opt. Lett. 44(21) 5181-5184 (2019)

Experimental characterization of a 400  Gbit/s orbital angular momentum multiplexed free-space optical link over 120 m

Yongxiong Ren, Zhe Wang, Peicheng Liao, Long Li, Guodong Xie, Hao Huang, Zhe Zhao, Yan Yan, Nisar Ahmed, Asher Willner, Martin P. J. Lavery, Nima Ashrafi, Solyman Ashrafi, Robert Bock, Moshe Tur, Ivan B. Djordjevic, Mark A. Neifeld, and Alan E. Willner
Opt. Lett. 41(3) 622-625 (2016)

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)