Abstract
In this paper, we propose an adaptive multiple-input–multiple-output (MIMO) free-space optical (FSO) links using an orbital-angular-momentum (OAM)-multiplexed based on the spatial-mode multiplexing (SMM) through the turbulent channel. We propose to use the SMM and spatial-mode diversity (SMD) combined with an adaptive MIMO technique to mitigate the atmospheric turbulence effects. In this paper, our objective is to design the adaptive MIMO–FSO links based on OAM–MIMO/SMM multiplexed and analyze its performance in the atmospheric turbulence conditions. The simulation results show four OAM modes-based MIMO/SMM and resulting in four OAM-multiplexed channels. Each OAM mode carries a 100-Gbit/s quadrature phase-shift keying signal (aggregate 400 Gbit/s) on a single wavelength channel ( $\lambda \sim 1550$ nm) and is transmitted for a 2-km link. The calculated received power and inter-channel crosstalk of an OAM–MIMO/SMM signal fluctuate by 4.5 −6 dB, respectively. The power penalties can be reduced by 1–4 dB for all channels after OAM–MIMO/SMM equalization at a bit-error rate (BER) of 10−9. The calculating results show that the system using an OAM-based MIMO/SMM and SMD multiplexing achieves superior BER performance using an adaptive MIMO/SMM equalization. The Numerical results show favorable transmission performance of OAM based on MIMO/SMM and the SMD multiplexing compared to the conventional-MIMO (CMIMO) of FSO transmission link. The Simulation models verified the superior BER performance of OAM–SMD-based MIMO/SMM. The SMM/MIMO–SMD technique performed better in the channel capacity and signal-to-noise ratios over other commonly used CMIMO algorithms. To sufficiently discuss the OAM–MIMO/SMM behavior-based SMD multiplexing, the performance of the novel SMM/MIMO–SMD technique is analyzed using simulations based on the Matlab/simulink program in order to verify the accuracy of the models and simulation results. This paper could be useful for the practical implementation of the SMM and the SMD using an adaptive MIMO equalization in the FSO systems.
Highlights
Free-space optical (FSO) communication systems can potentially benefit from the transmission of multiple spatiallyThe associate editor coordinating the review of this manuscript and approving it for publication was Honglong Chen.orthogonal beams and orbital-angular-momentum (OAM)multiplexed beams through a single aperture pair where the channel capacity is multiplied by the number of OAM modes [1]–[7]
The algorithm is validated by the program developed by Matlab, and the results show that the model can be accurately and effectively supported
WORK We have investigated the high-speed of an OAM and adaptive multipleinput and multi-output (MIMO)-based Spatial-mode multiplexing (SMM)/spatial-mode diversity (SMD) multiplexed free-space optical link, enabled by adaptive optics, lowdensity parity check (LDPC)-coded OAM-based transmission system, and SMD
Summary
Free-space optical (FSO) communication systems can potentially benefit from the transmission of multiple spatiallyThe associate editor coordinating the review of this manuscript and approving it for publication was Honglong Chen.orthogonal beams and orbital-angular-momentum (OAM)multiplexed beams through a single aperture pair where the channel capacity is multiplied by the number of OAM modes [1]–[7]. When beams-carrying OAM and MIMO-based SMM multiplexing are transmitted in the FSO links, the AT will modify the phase structure of OAM modes, the power of one OAM state spread to the other OAM states [19]. The adaptive optics and channel coding are commonly used to mitigate the AT effects of an OAM-based MIMO multiplexed FSO communication links. Qu demonstrated a turbulence mitigation scheme by a lowdensity parity check (LDPC) coded OAM-based transmission system and an AO [22], [23] Using this model, we maximize the overall channel capacity for the optimal set of OAM mode numbers [24], [25]. We analyze the performance of FSO communication link using an OAM–MIMO/SMM beam based on an adaptive MIMO equalization with non-zero radial index [26]. Simulation results show that in 2 km OAM–MIMO/ SMM-based FSO links, using transmitter lenses to focus
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