Security enhancement for adaptive optics aided longitudinal orbital angular momentum multiplexed underwater wireless communications

Abstract

The frozen-wave-based longitudinal orbital angular momentum multiplexing (LOAMM) system developed in [IEEE Photonics J. 10, 7900416 (2018)10.1109/JPHOT.2017.2778238] has the potential to overcome the crosstalk effects induced by turbulence. In this paper, we propose a defocus measurement aided adaptive optics (DMA-AO) technique for turbulence compensation in a LOAMM underwater wireless optical communication (UWOC) system to investigate the enhancement of physical layer security. Relying on a phase retrieval algorithm and probe beam, three amplitude-only measurements obtained from different back focus planes can realize phase reconstruction of distorted OAM beams. Moreover, the so-called mixture generalized gamma-Johnson S B (GJSB) distribution is proposed to characterize the probability density function (PDF) of reference-channel irradiance of OAM. The GJSB allows for obtaining closed-form and analytically tractable expression for the probability of strictly positive secrecy capacity (SPSC) in a single input single output (SISO) system. Furthermore, the average secrecy capacity (ASC) and probability of SPSC for a multiple input multiple output (MIMO) system are investigated. Compared to the traditional OAM multiplexing system based on Laguerre-Gaussian (LG) beams, the LOAMM system with a probe beam assisted DMA-AO technique has potential advantages for improving the security performance in UWOC.

Analysis of Optical Wireless Communication Links in Turbulent Underwater Channels With Wide Range of Water Parameters

“…The impact of spatial diversity techniques for orbital angular momentum (OAM) beams was investigated in [30] and significant improvement in the average channel capacity, BER and outage probability was reported. The unified statistical method related studies for optical wireless communication was also performed for adaptive optics that remains an important tool in terms of mitigating the turbulence effect [31], [32]. In [31], a defocud measurement aided adaptive optics compensation methdod was proposed for an OAM-based UWOC system to mitigate the turbulence induced crosstalk effect and to improve the security performance.…”

“…The unified statistical method related studies for optical wireless communication was also performed for adaptive optics that remains an important tool in terms of mitigating the turbulence effect [31], [32]. In [31], a defocud measurement aided adaptive optics compensation methdod was proposed for an OAM-based UWOC system to mitigate the turbulence induced crosstalk effect and to improve the security performance. The average BER, outage porobability and ergodica capacity of an OAM-based coherent UWOC link operating in Internet of Underwater Things (IoUT) system was studied in [32] and a noticeable performance improvement was obtained with the application of random-amplitude-masksbased adaptive optics technique.…”

Double and Square Bessel–Gaussian Beams

“…Therefore, extending the set of different types and modifications of BG beams is a relevant problem. In [ 20 ], modified BG beams called “frozen waves” were studied. In [ 21 ], the propagation of asymmetric BG beams [ 22 , 23 ] in a turbulent atmosphere was considered.…”

Deep Learning Recognition of Orbital Angular Momentum Modes Over Atmospheric Turbulence Channels Assisted by Vortex Phase Modulation

“…However, in real FSO communication scenarios, the beams propagating through air may be distorted by atmospheric turbulence [6], [7], which brings difficulty to the detection and decision of OAM states [8], [9]. To mitigate the turbulence-induced distortions, multiple compensation methods have been proposed, such as the adaptive optics compensation method [10]- [14], the algorithm based compensation method [15]- [18], and the auto-alignment system method [19]. These methods have been proved effective in recovering the deformed OAM modes to increase the mode purity and ease the OAM detection.…”