Special Issue "Optical Wireless Communication (OWC) Systems"

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Optical Communication and Network".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 7109

Special Issue Editors

Prof. Dr. Hai-Han Lu
E-Mail Website
Guest Editor
Department of Electro-Optical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
Interests: Optical Wireless Communication (OWC); fiber-FSO convergence; Underwater Wireless Optical Communications (UWOC)
Prof. Dr. Chi-Wai Chow
E-Mail Website
Guest Editor
Department of Photonics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
Interests: optical wireless communication (OWC); visible light communication (VLC); silicon photonics (SiPh)
Prof. Dr. Liankuan Chen
E-Mail Website
Guest Editor
Department of Information Engineering, The Chinese University of Hong Kong, Hong Kong, China
Interests: optical wireless communications; next generation access networks; advanced modulation formats and signal processing; optical performance monitoring and management; network optimization; biophotonics

Special Issue Information

Dear Colleagues,

There is a growing interest in the research and development of optical wireless communication (OWC) systems, including free-space optical communications (FSO), visible light communications (VLC), and underwater wireless optical communications (UWOC). This is mainly due to significant advancements in optical sources from high-performance light-emitting diodes (LED), solid-state laser diodes (LD), and high-speed photodiodes (PD) in different optical spectra (i.e., infrared, visible, ultraviolet). Exploring these new optical spectra for the purpose of wireless communication is a big interdisciplinary research challenge. Additionally, due to the storage of traditional radiofrequency (RF) communication spectra, using optical spectra for wireless communication can also release the heavy burden of RF wireless communication. OWC technologies, such as optical camera communication (OCC) and image sensor-based Internet of Things (IoT), visible light positioning (VLP) has received much attention recently. Light fidelity (LiFi), as a special form of OWC, is emerging to provide a high-speed wireless link, supporting multiuser and bidirectional access. It may also be integrated into the future 6G mobile networks.

This Special Issue plans to focus on short- to long-reach OWC, from indoor to outdoor, from ground and underwater. Topics of interest include but are not limited to:

  • Optical wireless communication (OWC) systems;
  • Free-space optical communications (FSO);
  • Visible light communications (VLC);
  • Underwater wireless optical communications (UWOC);
  • Optical beam forming, beam steering, and diverging;
  • LiFi network technologies;
  • Hybrid LiFi/Rario-over-Fiber (RoF) technologies;
  • Visible light positioning (VLP);
  • Optical camera communication (OCC);
  • Screen or camera communication;
  • Real-time communication system;
  • Optical components or coating techniques for optical wireless communication.

Prof. Dr. Hai-Han Lu
Prof. Dr. Chi-Wai Chow
Prof. Dr. Liankuan Chen
Guest Editors

Manuscript Submission Information

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Keywords

  • optical wireless communication
  • visible light communication
  • optical wireless positioning
  • free-space optical communications
  • camera communication
  • underwater wireless optical communications
  • optical components
  • optical coating

Published Papers (7 papers)

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Research

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Article
A Mixed FSO/RF Integrated Satellite-High Altitude Platform Relaying Networks for Multiple Terrestrial Users with Presence of Eavesdropper: A Secrecy Performance
Photonics 2022, 9(1), 32; https://doi.org/10.3390/photonics9010032 - 04 Jan 2022
Cited by 4 | Viewed by 558
Abstract
In this paper, the secrecy performance of a mixed free space optical (FSO)/radio frequency (RF) integrated satellite-high altitude platform (HAP) relaying networks for terrestrial multiusers with the existence of an eavesdropper is investigated. In this network, FSO is adopted to establish the link [...] Read more.
In this paper, the secrecy performance of a mixed free space optical (FSO)/radio frequency (RF) integrated satellite-high altitude platform (HAP) relaying networks for terrestrial multiusers with the existence of an eavesdropper is investigated. In this network, FSO is adopted to establish the link between the satellite and HAP for which it experiences Gamma-Gamma distributions under different detection schemes (i.e., heterodyne and intensity modulation direct detection). The transmission between the amplify-and-forward (AF) relaying HAP and terrestrial multiusers is through the RF and is modeled as shadowed-Rician fading distribution. Owning to broadcasting nature of RF link, it is assumed that an eavesdropper attempts to intercept the users’ confidential message, and the eavesdropper link is subjected to Rician distributions. Specifically, the closed-form expression for the system equivalent end-to-end cumulative distribution function is derived by exploiting the Meijer’s G and Fox’s H functions. Based on this expression, the exact closed-form expressions of the system connection outage probability, secrecy outage probability, and strictly positive secrecy capacity are obtained under the different detection schemes at HAP. Moreover, the asymptotic analyze of the system secrecy outage probability is provided to obtain more physical insights. Furthermore, the accuracy of all the derived analytical closed-form expressions is verified through the Monte-Carlo simulations. In addition, the impact of atmospheric turbulence, pointing errors, shadowing severity parameters, and Rician factor are thoroughly evaluated. Under the same system conditions, the results depict that heterodyne detection outperforms the intensity modulation direct detection. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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Article
Hybrid Ring- and Tree-Topology RoF Transmission System with Disconnection Protection
Photonics 2021, 8(11), 515; https://doi.org/10.3390/photonics8110515 - 16 Nov 2021
Viewed by 580
Abstract
This paper proposes a hybrid ring- and tree-topology radio over fiber (RoF) transmission system with self-disconnection protection that can support the high distribution density of base stations (BSs) in a metropolitan area and strengthen the network quality of service through self-disconnection protection. The [...] Read more.
This paper proposes a hybrid ring- and tree-topology radio over fiber (RoF) transmission system with self-disconnection protection that can support the high distribution density of base stations (BSs) in a metropolitan area and strengthen the network quality of service through self-disconnection protection. The number of supportable BS in the system can be increased significantly by integrating the time- and wavelength-division multiplexing techniques and properly utilizing a new-generation single-line bidirectional add/drop multiplexer (SBOADM) into the proposed system. Moreover, when the ring–fiber link of the system is interrupted for any reason, the system operator can recover the broken connections quickly only by transforming an optical switch state at the CO end to allow the downlink optical signals to transmit along the clockwise and counterclockwise directions of the ring–fiber link simultaneously. In this case, the downstream optical signals can be delivered to each set of BS-groups through the two-way transmission characteristics of the SBOADM automatically, and the uplink optical signals, originally, from each set of BS-groups can be transmitted back to the CO end along the opposite direction of the downlink signal-routing path. In this way, the interference caused by fiber breakage can be avoided immediately, and the entire transport system can be reconnected to ensure the quality of network services. Our experimental results prove that the overall transmission performances are similar to those under normal circumstances. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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Communication
High Speed Visible Light Communication Using Digital Power Domain Multiplexing of Orthogonal Frequency Division Multiplexed (OFDM) Signals
Photonics 2021, 8(11), 500; https://doi.org/10.3390/photonics8110500 - 08 Nov 2021
Cited by 7 | Viewed by 822
Abstract
In order to increase transmission capacity, multiplexing schemes in different physical dimensions, including time, frequency, modulation quadrature, polarization, and space, can be employed. In this work, we propose and demonstrate a red color laser-diode (LD) based visible-light-communication (VLC) system using two kinds of [...] Read more.
In order to increase transmission capacity, multiplexing schemes in different physical dimensions, including time, frequency, modulation quadrature, polarization, and space, can be employed. In this work, we propose and demonstrate a red color laser-diode (LD) based visible-light-communication (VLC) system using two kinds of digital domain multiplexing schemes, orthogonal-frequency-division-multiplexing (OFDM) and power-domain division-multiplexing (PowDM). The two digital domain multiplexed data can achieve data rates of 1.66 Gbit/s and 6.41 Gbit/s, respectively, providing a total data rate of 8.07 Gbit/s, fulfilling the pre-forward error correction (pre-FEC) bit-error-rate (BER) limit. The measured signal-to-noise ratios (SNRs) are 10.96 dB and 14.45 dB, respectively. Here, similar to OFDM, the PowDM can enhance the total system capacity by allowing acceptable signal spectra overlapping among different power division signals to maximize the bandwidth utilization. An experiment to verify and evaluate the proposed work is performed. The modulation and demodulation of OFDM and PowDM are discussed. The optimum power levels of the individual signals in the PowDM signal are also analyzed. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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Article
Optical Wireless Communications Using Signal Space Diversity with Spatial Modulation
Photonics 2021, 8(11), 468; https://doi.org/10.3390/photonics8110468 - 22 Oct 2021
Cited by 4 | Viewed by 587
Abstract
A signal space diversity (SSD) scheme was proposed to be incorporated with spatial modulation (SM) in an intensity-modulation/direct-detection-based multiple-input-single-output (MISO) indoor optical wireless communication (OWC) system to improve bit-error-rate (BER) performance and system throughput. SSD was realized via signal constellation rotation and diversity [...] Read more.
A signal space diversity (SSD) scheme was proposed to be incorporated with spatial modulation (SM) in an intensity-modulation/direct-detection-based multiple-input-single-output (MISO) indoor optical wireless communication (OWC) system to improve bit-error-rate (BER) performance and system throughput. SSD was realized via signal constellation rotation and diversity interleaving using different channel gains to improve the BER. With SM incorporated, the MISO-OWC system throughput increased. Theoretical BER expressions of the SSD scheme were established for the first time by investigating the distance of neighboring constellation symbols upon maximum-likelihood detection. Such BER expressions were further verified by numerical results. The results showed that, except for the slightly-lower-accuracy performance brought by comparable distances of neighboring constellation symbols in cases of low signal-to-noise ratios, these BER expressions were accurate in most scenarios. Moreover, theoretical investigations of channel gain distributions were performed at different signal constellation rotation angles to show the capability of the SSD scheme to improve the BER. The results showed that a significantly improved BER by two orders of magnitude could be achieved using a reasonably high channel-gain ratio and a larger constellation rotation angle. The SSD-SM scheme provides a promising option to achieve transmitter diversity with an enhanced throughput in high-speed indoor OWC systems. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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Article
Study of the Performance of Deep Learning-Based Channel Equalization for Indoor Visible Light Communication Systems
Photonics 2021, 8(10), 453; https://doi.org/10.3390/photonics8100453 - 18 Oct 2021
Cited by 6 | Viewed by 728
Abstract
The inherent impairments of visible light communication (VLC) in terms of nonlinearity of light-emitting diode (LED) and the optical multipath restrict bit error rate (BER) performance. In this paper, a model-driven deep learning (DL) equalization scheme is proposed to deal with the severe [...] Read more.
The inherent impairments of visible light communication (VLC) in terms of nonlinearity of light-emitting diode (LED) and the optical multipath restrict bit error rate (BER) performance. In this paper, a model-driven deep learning (DL) equalization scheme is proposed to deal with the severe channel impairments. By imitating the block-by-block signal processing block in orthogonal frequency division multiplexing (OFDM) communication, the proposed scheme employs two subnets to replace the signal demodulation module in traditional system for learning the channel nonlinearity and the symbol de-mapping relationship from the training data. In addition, the conventional solution and algorithm are also incorporated into the system architecture to accelerate the convergence speed. After an efficient training, the distorted symbols can be implicitly equalized into the binary bits directly. The results demonstrate that the proposed scheme can address the overall channel impairments efficiently and can recover the original symbols with better BER performance. Moreover, it can still work robustly when the system is complicated by serious distortions and interference, which demonstrates the superiority and validity of the proposed scheme in channel equalization. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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Article
ML-Based Identification of Structured Light Schemes under Free Space Jamming Threats for Secure FSO-Based Applications
Photonics 2021, 8(4), 129; https://doi.org/10.3390/photonics8040129 - 19 Apr 2021
Cited by 2 | Viewed by 941
Abstract
This paper exploits for the first time the use of machine learning (ML) based techniques to identify complex structured light patterns under free space optics (FSO) jamming attacks for secure FSO-based applications. Five M-ary modulation schemes, construed using Laguerre and Hermite Gaussian [...] Read more.
This paper exploits for the first time the use of machine learning (ML) based techniques to identify complex structured light patterns under free space optics (FSO) jamming attacks for secure FSO-based applications. Five M-ary modulation schemes, construed using Laguerre and Hermite Gaussian (LG and HG) mode families, were used in this investigation. These include 8-ary LG, 8-ary superposition-LG, 16-ary HG, 16-ary LG and superposition-LG, and 32-ary LG and superposition-LG and HG formats. The work was conducted using experimental demonstrations for two different jammer positions. The convolutional neural network (CNN)-based ML method was utilized to differentiate between the stressed mode patterns. The experimental results show a 100% recognition accuracy for 8-ary LG, 8-ary superposition-LG, and 16-ary HG at 1, −2, and −2 dB signal-to-jammer ratios (SJR), respectively. For SJR values < 0 dB, the standard LG modes are the most affected by jamming and are not recommended for data transmission in such an environment. Besides, the accuracy of determining the jammer direction of arrival was investigated using CNN and a simpler classifier based on linear discriminant analysis (LDA). The results show that advanced networks (e.g., CNN) are required to achieve reliable performance of 100% direction determination accuracy, at −5 dB SJR, as opposed to 97%, at 2 dB SJR, for a simple LDA classifier. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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Other

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Letter
Intensity and Coherence Characteristics of a Radial Phase-Locked Multi-Gaussian Schell-Model Vortex Beam Array in Atmospheric Turbulence
Photonics 2021, 8(1), 5; https://doi.org/10.3390/photonics8010005 - 29 Dec 2020
Cited by 5 | Viewed by 1177
Abstract
The theoretical descriptions for a radial phase-locked multi-Gaussian Schell-model vortex (RPLMGSMV) beam array is first given. The normalized intensity and coherence distributions of a RPLMGSMV beam array propagating in free space and atmospheric turbulence are illustrated and analyzed. The results show that a [...] Read more.
The theoretical descriptions for a radial phase-locked multi-Gaussian Schell-model vortex (RPLMGSMV) beam array is first given. The normalized intensity and coherence distributions of a RPLMGSMV beam array propagating in free space and atmospheric turbulence are illustrated and analyzed. The results show that a RPLMGSMV beam array with larger total number N or smaller coherence length σ can evolve into a beam with better flatness when the beam array translating into the flat-topped profile at longer distance z and the flatness of the flat-topped intensity distribution can be destroyed by the atmospheric turbulence at longer distance z. The coherence distribution of a RPLMGSMV beam array in atmospheric turbulence at the longer distance will have Gaussian distribution. The research results will be useful in free space optical communication using a RPLMGSMV beam array. Full article
(This article belongs to the Special Issue Optical Wireless Communication (OWC) Systems)
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