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Advanced Technologies in Optical Wireless Communications—2nd Edition

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

Deadline for manuscript submissions: 31 December 2026 | Viewed by 8078

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Editors

Dr. Cuiwei He

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Guest Editor

School of Information Science, Japan Advanced Institute of Science and Technology (JAIST), Ishikawa, Japan
Interests: optical wireless communications
Special Issues, Collections and Topics in MDPI journals

Dr. Chengwei Fang

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Guest Editor

School of Engineering, Royal Melbourne Institute of Technology (RMIT) University, Melbourne, VIC 3000, Australia
Interests: optical wireless communications; visible light communications; underwater OWC

Dr. Ke Wang

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Guest Editor

School of Engineering, Royal Melbourne Institute of Technology (RMIT) University, Melbourne, VIC 3000, Australia
Interests: optical wireless communications; optical integrated sensing and communication; optical neuromorphic sensing and communication; silicon photonic integration; microwave photonics; optical interconnects

Dr. Chen Chen

E-Mail Website
Guest Editor

School of Microelectronics and Communication Engineering, Chongqing University, Chongqing, China
Interests: visible light communication; optical wireless communication; orthogonal frequency division multiplexing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Optical wireless communication (OWC) has emerged as a compelling solution to meet the increasing global demand for high-capacity, low-latency, and spectrum-efficient communication technologies. With the use of the unlicensed optical spectrum, OWC enables ultra-high-speed links across diverse environments, including indoor networks, underwater communication, vehicular systems, mobile access, and space communication. Recent advances in device technologies, modulation techniques, photonic signal processing, and AI-driven optimization are rapidly expanding the boundaries of achievable performance, making OWC a key technology for beyond-5G/6G communication systems. This Special Issue invites original research articles, reviews, and perspective papers that address theoretical, experimental, and system-level advances in all areas of OWC. Contributions that demonstrate new enabling devices, architectures, algorithms, and applications are especially welcome. We look forward to receiving your contributions.

Dr. Cuiwei He
Dr. Chengwei Fang
Dr. Ke Wang
Dr. Chen Chen
Guest Editors

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Keywords

free-space optical (FSO) communication
visible light communication (VLC) and LiFi
underwater optical wireless communication (UOWC)
system design and signal processing
devices and components

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Published Papers (8 papers)

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Research

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37 pages, 1015 KB

Open AccessArticle

LED-Based Polar Coded Wireless Quantum Optical Communications for 6G and Beyond

by Kushtrim Dini, Hamza Almujahed and Peter Jung

Photonics 2026, 13(7), 619; https://doi.org/10.3390/photonics13070619 - 27 Jun 2026

Viewed by 251

Abstract

Wireless communication above

300 GHz

requires highly sophisticated analog circuit design due to severe frequency dependent ohmic losses. The complexity of such electronic hardware motivates exploring wireless quantum optical communication approaches even for the 6G “terahertz (THz) range”

[300 GHz, 10 THz]

[...] Read more.

Wireless communication above

300 GHz

[300 GHz, 10 THz]

. In this work, the classical radio frequency (RF)-based inner physical layer (PHY) transceiver blocks of channel coded wireless communication systems are replaced by wireless quantum optical transceiver blocks. Short range concepts employing LEDs as transmitters are particularly attractive, owing to their low implementation cost and practical simplicity. In contrast to laser based wireless quantum optical transmission over multipath channels, the quantum mechanical density operator

{\underset{̲}{ρ}}_{RX, [s_{i}, b_{i}]}

and the transition probability

γ (s_{i}, s_{i + 1})

required by the quantum data detection must be revised accordingly. Furthermore, the novel interpretation introduced here, in which the extrinsic information is treated as a diversity branch rather than as an estimate of the a priori information, facilitates turbo equalization that still can accomodate varying a priori information. However, due to the limited uncoded transmission performance achievable with such systems, the incorporation of sophisticated channel coding schemes appears imperative. The authors therefore investigate the combination of sophisticated channel coding techniques, such as polar coding, with LED based wireless quantum optical transmission technologies. All numerical results assume a cryogenically cooled receiver front-end (approximately 10 K), yielding thermal noise levels. Operation at room temperature in the 6G THz range

[300 GHz, 10 THz]

would require an average number

{\bar{N}}_{α}

of thermal noise photon values of approximately 5 to 20, which is beyond the scope of this feasibility study. The results show that the proposed paradigm enables simple, robust, and practically viable wireless quantum optical communication systems with favorable transmission performance. Additional gains are achieved through iterative turbo equalization. The results also suggest that the proposed approach can pave the way toward robust and economically viable future communication solutions. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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28 pages, 1108 KB

Open AccessArticle

Risk-Aware Illumination-Constrained Resource Allocation for Hybrid VLC/RF Indoor Networks Under Random Optical Blockage

by Tingting Qin and Yang Tu

Photonics 2026, 13(6), 569; https://doi.org/10.3390/photonics13060569 - 10 Jun 2026

Viewed by 269

Abstract

Indoor visible light communication (VLC) has attracted increasing attention as a promising wireless access technology because of its large unlicensed bandwidth and dual functionality of illumination and data transmission. However, practical VLC systems are vulnerable to line-of-sight (LoS) blockage caused by user mobility, human shadowing, and indoor obstacles, which may degrade link reliability and service continuity. Although hybrid VLC/RF networks can improve robustness by using RF transmission as a backup link, excessive RF fallback under severe optical blockage may overload the bandwidth-limited RF interface and reduce the service quality of RF-associated users. To address this issue, this paper investigates a risk-aware illumination-constrained resource allocation scheme for hybrid VLC/RF indoor networks under random optical blockage. A unified system model is developed by considering Lambertian optical propagation, random optical blockage, RF backup transmission, and working-plane illumination constraints. Based on this model, a joint user association and power allocation problem is formulated under QoS, transmit-power, and illumination requirements. The proposed scheme evaluates VLC service utility under blockage uncertainty, controls RF fallback to avoid excessive backup-link loading, allocates VLC/RF transmission power, and performs illumination feasibility adjustment to preserve the required lighting level. Simulation results show that, under severe blockage conditions, the proposed scheme reduces the outage probability to approximately 0.26, compared with 0.68 for VLC-only transmission and 0.47 for threshold-based VLC/RF switching. For a 20-user network, the proposed scheme achieves an average sum rate of approximately 277 Mbps, maintains a 100% illumination compliance ratio, and achieves higher energy efficiency than the benchmark schemes. Further RF backup analysis shows that the proposed scheme can maintain the service quality of RF-associated users by avoiding excessive RF fallback. These results demonstrate the effectiveness of the proposed framework for reliable and illumination-feasible hybrid VLC/RF indoor communication. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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18 pages, 13038 KB

Open AccessArticle

Reconfigurable Broadband Signal Channelized Reception Technology Based on Parallel Mach–Zehnder Modulators (MZMs)

by Peiqi Li, Ming Hou, Jiahong Zhang, Di Ma and Yingna Li

Photonics 2026, 13(5), 465; https://doi.org/10.3390/photonics13050465 - 8 May 2026

Cited by 1 | Viewed by 603

Abstract

A reconfigurable broadband signal channelized reception technique based on parallel Mach–Zehnder modulators (MZMs) is proposed. In the upper branch, the unknown broadband signal is modulated onto the ±1st-order sidebands of a frequency-shifted optical carrier. In the lower branch, N parallel MZMs are employed, with each MZM generating two local oscillator (LO) comb lines, which beat with the broadband signal from the upper branch to produce 4N sub-channels. By adjusting the frequency shift of the acousto-optic frequency shifter (AOFS) and the frequency of the LO signals, the system achieves tunability over an operating frequency band of 8 to 40 GHz, enabling simultaneous tuning of the sub-channel bandwidth, the number of sub-channels, and their center frequencies. Simulation experiments show that this technique can down-convert a wideband signal with a frequency band of 12–16 GHz to eight intermediate frequency (IF) signals with eight center frequencies of 0.5 GHz and a bandwidth of 0.5 GHz and down-convert a wideband signal with a frequency band of 32–40 GHz to eight IF signals with eight center frequencies of 1 GHz and a bandwidth of 1 GHz, and the image rejection ratio (IRR) is greater than 26 dB, the passband power fluctuation is less than 0.5 dB, and the spurious-free dynamic range (SFDR) is 95.17 dB·Hz^2/3. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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11 pages, 1506 KB

Open AccessArticle

Study of Large Modulation Bandwidth GaN-Based Laser Diodes with Different Ridge Waveguide Structures

by Zhichong Wang, Junhui Hu, Zhen Yang, Anna Kafar, Piotr Perlin, Shuiqing Li, Heqing Deng, Jiangyong Zhang, Sha Shiong Ng, Mundzir Abdullah, Junwen Zhang, Nan Chi and Chao Shen

Photonics 2026, 13(4), 382; https://doi.org/10.3390/photonics13040382 - 16 Apr 2026

Viewed by 1108

Abstract

With the advent of 6G mobile communication, the demand for ultra-high bandwidth wireless communication has increased rapidly, drawing significant attention to visible light communication (VLC) as a promising emerging technology. GaN-based laser diodes (LDs) are regarded as high-speed light sources for VLC owing to their high modulation bandwidth and high optical power density. Apart from the active region design, the LD’s structure also plays a crucial role in determining their dynamic properties, which have yet to be thoroughly studied in III-nitride LDs. In this work, we systematically investigate InGaN/GaN laser diodes with three ridge waveguide configurations: a conventional single-ridge structure, a dual-ridge large-mesa structure, and a dual-ridge small-mesa structure. The threshold current, small-signal modulation bandwidth of devices with different structures are comparatively analyzed. Experimental results reveal that the double-ridge small mesa laser diode achieves a modulation bandwidth of −3 dB at 6.02 GHz. These results provide valuable insights into the structural optimization of GaN-based high-speed laser diodes and offer practical guidance for the development of high-performance, energy-efficient VLC transmitters. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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20 pages, 2605 KB

Open AccessArticle

Interference-Aware User Grouping and Power Allocation for Overlapping Multi-LED ADO-OFDM NOMA VLC Networks

by Yang Tu, Chuan Li and Cu Van Pham

Photonics 2026, 13(3), 241; https://doi.org/10.3390/photonics13030241 - 28 Feb 2026

Cited by 2 | Viewed by 649

Abstract

Overlapping illumination in multi-LED visible light communication (VLC) networks introduces cross-LED coupling that reshapes the received-signal composition and may trigger error propagation in successive interference cancellation (SIC) for layered ADO-OFDM NOMA. This work employs an overlap factor [...] Read more.

β \in [0, 1]

to quantify the severity of overlap-induced cross-LED coupling and develops a

β

-aware resource-allocation framework for a dual-LED indoor downlink. The proposed design integrates channel-aware MCGAD user grouping with three-level coefficient adaptation, including the inter-LED power split

η

, the inter-layer ACO/DCO split

ρ

, and the intra-layer two-user NOMA coefficients

α

. Monte Carlo evaluations over

β \in {0, 0.2, 0.5}

show that stronger coupling drives the system into an interference-limited regime with a pronounced high-SNR BER floor for strong users after SIC; the proposed

β

-aware design consistently reduces this floor relative to a

β

-blind fixed-coefficient baseline. Meanwhile, the spectral-efficiency curves remain close to the baseline, with only a minor gap at moderate-to-high SNR, and the Shannon-rate energy-efficiency trends remain comparable across coupling scenarios. The grouping-and-allocation procedure is dominated by sorting and deterministic pairing, exhibiting

O (U log U)

complexity and avoiding the combinatorial growth of exhaustive grouping. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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14 pages, 3075 KB

Open AccessArticle

A Novel Modulation Scheme Based on the Kramers–Kronig Relations for Optical IM-DD Systems

by Xiaohe Dong, Kuokuo Zhang and Caiming Sun

Photonics 2026, 13(3), 227; https://doi.org/10.3390/photonics13030227 - 26 Feb 2026

Viewed by 935

Abstract

The increasing demand for higher data rates in optical communication systems, especially within data centers and backbone networks, calls for the development of advanced modulation formats that can significantly enhance system performance. In this work, we introduce a novel modulation format based on the Kramers–Kronig relations, designed to improve upon traditional techniques such as Pulse Amplitude Modulation (PAM) and Carrier-less Amplitude Phase (CAP) modulation. The novel modulation format was rigorously validated through experimental investigations using an optical wireless communication (OWC) link. The results demonstrate a notable improvement in bit error rate (BER) performance and receiver sensitivity when compared to the conventional PAM-4 modulation scheme and CAP-16 modulation schemes. Moreover, the proposed scheme effectively reduces the complexity of digital filtering required by CAP while lowering the demands on the Digital-to-Analog Converter (DAC), making it a more practical solution for high-speed optical communication. This advancement facilitates higher data transmission rates, proving the Kramers–Kronig relations modulation format as a promising alternative to existing methods. Its potential for enhancing the efficiency and capacity of optical communication systems is evident. Future research will focus on optimizing the modulation parameters and exploring their application in more complex scenarios, such as high-speed underwater visible light communication systems, where advanced modulation formats are crucial for overcoming bandwidth limitations. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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25 pages, 896 KB

Open AccessArticle

Sequential Deep Learning with Feature Compression and Optimal State Estimation for Indoor Visible Light Positioning

by Negasa Berhanu Fite, Getachew Mamo Wegari and Heidi Steendam

Photonics 2026, 13(2), 211; https://doi.org/10.3390/photonics13020211 - 23 Feb 2026

Cited by 1 | Viewed by 1795

Abstract

Visible Light Positioning (VLP) is widely regarded as a promising technology for high-precision indoor localization due to its immunity to radio-frequency interference and compatibility with existing Light-Emitting Diode (LED) lighting infrastructure. Despite recent progress, current VLP systems remain fundamentally limited by nonlinear received signal strength (RSS) characteristics, unknown transmitter orientations, and dynamic indoor disturbances. Existing solutions typically address these challenges in isolation, resulting in limited robustness and scalability. This paper proposes SCENE-VLP (Sequential Deep Learning with Feature Compression and Optimal State Estimation), a structured positioning framework that integrates feature compression, temporal sequence modeling, and probabilistic state refinement within a unified estimation pipeline. Specifically, SCENE-VLP combines Principal Component Analysis (PCA) and Denoising Autoencoders (DAE) for linear and nonlinear observation conditioning, Gated Recurrent Units (GRU) for modeling temporal dependencies in RSS sequences, and Kalman-based filtering (KF/EKF) for recursive state-space refinement. The framework is formulated as a hierarchical approximation of the nonlinear observation model, linking data-driven measurement learning with Bayesian state estimation. A systematic ablation study across multiple scenarios, including same-dataset evaluation and cross-dataset generalization, demonstrates that each component provides complementary benefits. Feature compression reduces redundancy while preserving dominant signal structure; GRU significantly improves robustness over static regression; and recursive filtering consistently reduces positioning error compared to unfiltered predictions. While both KF and EKF improve performance, EKF provides incremental refinement under mild nonlinearities. Extensive simulations conducted on an indoor dataset collected from a realistic deployment with eight ceiling-mounted LEDs and a single photodetector (PD) show that SCENE-VLP achieves sub-decimeter localization accuracy, with P50 and P95 errors of 1.84 cm and 6.52 cm, respectively. Cross-scenario evaluation further confirms stable generalization and statistically consistent improvements. These results demonstrate that the structured integration of observation conditioning, temporal modeling, and Bayesian refinement yields measurable gains beyond partial pipeline configurations, establishing SCENE-VLP as a robust and scalable solution for next-generation indoor visible light positioning systems. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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Review

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35 pages, 2107 KB

Open AccessReview

A Review of the Structure of Free-Space Optical Channel Models: Physical Meaning, Assumptions, and Atmospheric Conditions

by Sabai Phuchortham and Hakilo Sabit

Photonics 2026, 13(5), 425; https://doi.org/10.3390/photonics13050425 - 26 Apr 2026

Viewed by 1577

Abstract

Free-space optical (FSO) communication is an attractive high-capacity wireless technology for terrestrial, aerial, and satellite links. However, FSO performance is strongly affected by multiple impairments, including path loss, turbulence attenuation, pointing errors, and equipment loss. Therefore, accurate performance evaluation requires channel modelling that accounts for both deterministic power losses and stochastic channel effects. This paper presents a comprehensive and structured review of FSO channel modelling, covering the transmission, propagation medium, and receiver sections. The composite channel response is represented using a mathematical formulation. Commonly used FSO models are reviewed and organised, including Beer–Lambert and geometrical loss, Kim and Kruse path loss models, Lognormal, Gamma–Gamma, K, and Málaga distributions, along with pointing-error and angle-of-arrival models. Each model is explained in terms of its physical meaning, assumptions, and applicable operating conditions. Lastly, a numerical example is presented to demonstrate how deterministic losses and stochastic channel effects can be combined in FSO performance evaluation. Full article

(This article belongs to the Special Issue Advanced Technologies in Optical Wireless Communications—2nd Edition)

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