1.
Safi, Hossein; Babadi, Sina; Osahon, Isaac N. O.; Sparks, Adrian; Kostakis, Ioannis; Powell, Denise; Meredith, Wyn; Missous, Mohamed; Missous, Medi; Tavakkolnia, Iman; Haas, Harald
Chip-scale beam-shaped optical wireless system for high-speed and energy-efficient connectivity Journal Article
In: Advanced Photonics Nexus, vol. 5, no. 02, 2026, ISSN: 2791-1519.
Links | BibTeX | Tags: LRDC, optical wireless communication (OWC), orthogonal frequency-division multiplexing, Photonics, vertical-cavity surface-emitting lasers
@article{safi_chip-scale_2026,
title = {Chip-scale beam-shaped optical wireless system for high-speed and energy-efficient connectivity},
author = {Hossein Safi and Sina Babadi and Isaac N. O. Osahon and Adrian Sparks and Ioannis Kostakis and Denise Powell and Wyn Meredith and Mohamed Missous and Medi Missous and Iman Tavakkolnia and Harald Haas},
url = {https://www.spiedigitallibrary.org/journals/advanced-photonics-nexus/volume-5/issue-02/026018/Chip-scale-beam-shaped-optical-wireless-system-for-high-speed/10.1117/1.APN.5.2.026018.full},
doi = {10.1117/1.APN.5.2.026018},
issn = {2791-1519},
year = {2026},
date = {2026-03-01},
urldate = {2026-03-18},
journal = {Advanced Photonics Nexus},
volume = {5},
number = {02},
keywords = {LRDC, optical wireless communication (OWC), orthogonal frequency-division multiplexing, Photonics, vertical-cavity surface-emitting lasers},
pubstate = {published},
tppubtype = {article}
}
2.
Safi, Hossein; Ahmad, Rizwana; Tavakkolnia, Iman; Haas, Harald
Q-Learning for 3D Coverage in VCSEL-based Optical Wireless Systems Miscellaneous
2026.
Abstract | Links | BibTeX | Tags: FOS: Mathematics, LRDC, optical wireless communication (OWC), Optimization and Control (math.OC), vertical-cavity surface-emitting lasers
@misc{safi_q-learning_2026,
title = {Q-Learning for 3D Coverage in VCSEL-based Optical Wireless Systems},
author = {Hossein Safi and Rizwana Ahmad and Iman Tavakkolnia and Harald Haas},
url = {https://arxiv.org/abs/2602.03526},
doi = {10.48550/ARXIV.2602.03526},
year = {2026},
date = {2026-01-01},
urldate = {2026-06-03},
publisher = {arXiv},
abstract = {Beam divergence control is a key factor in maintaining reliable coverage in indoor optical wireless communication (OWC) systems as receiver height varies.Conventional systems employ fixed divergence angles, which result in significant coverage degradation due to the non-convex tradeoff between optical power concentration and spatial spread. In this paper, we introduce a reinforcement learning (RL)-based framework for dynamic divergence adaptation in vertical-cavity surface-emitting laser (VCSEL)-based OWC networks. By continuously interacting with the environment, the RL agent autonomously learns a near-optimal mapping between receiver height and beam divergence, thereby eliminating the need for analytical modeling or computationally intensive exhaustive search. Simulation results demonstrate that the proposed approach achieves up to 92% coverage at low receiver heights and maintains robust performance under challenging conditions, enabling scalable, real-time, and energy-efficient beam control for dense VCSEL array deployments in next-generation OWC systems.},
keywords = {FOS: Mathematics, LRDC, optical wireless communication (OWC), Optimization and Control (math.OC), vertical-cavity surface-emitting lasers},
pubstate = {published},
tppubtype = {misc}
}
Beam divergence control is a key factor in maintaining reliable coverage in indoor optical wireless communication (OWC) systems as receiver height varies.Conventional systems employ fixed divergence angles, which result in significant coverage degradation due to the non-convex tradeoff between optical power concentration and spatial spread. In this paper, we introduce a reinforcement learning (RL)-based framework for dynamic divergence adaptation in vertical-cavity surface-emitting laser (VCSEL)-based OWC networks. By continuously interacting with the environment, the RL agent autonomously learns a near-optimal mapping between receiver height and beam divergence, thereby eliminating the need for analytical modeling or computationally intensive exhaustive search. Simulation results demonstrate that the proposed approach achieves up to 92% coverage at low receiver heights and maintains robust performance under challenging conditions, enabling scalable, real-time, and energy-efficient beam control for dense VCSEL array deployments in next-generation OWC systems.
3.
Kazemi, Hossein; Younus, Othman; Osahon, Isaac N. O.; Ledentsov, Nikolay; Titkov, Ilya; Ledentsov, Nikolay; Haas, Harald
Demonstrating 80 Gb/s Optical Wireless Communication Using A Multi-Aperture VCSEL and A Multi-Mode Fiber-Coupled Receiver for Next-Generation LiFi Connectivity Proceedings Article
In: Optical Fiber Communication Conference (OFC) 2026, pp. M3H.2, Optica Publishing Group, Los Angeles, California, 2026, ISBN: 9781957171548.
Abstract | Links | BibTeX | Tags: LiFi, LRDC, optical wireless communication (OWC), vertical-cavity surface-emitting lasers
@inproceedings{kazemi_demonstrating_2026,
title = {Demonstrating 80 Gb/s Optical Wireless Communication Using A Multi-Aperture VCSEL and A Multi-Mode Fiber-Coupled Receiver for Next-Generation LiFi Connectivity},
author = {Hossein Kazemi and Othman Younus and Isaac N. O. Osahon and Nikolay Ledentsov and Ilya Titkov and Nikolay Ledentsov and Harald Haas},
url = {https://opg.optica.org/abstract.cfm?URI=OFC-2026-M3H.2},
doi = {10.1364/OFC.2026.M3H.2},
isbn = {9781957171548},
year = {2026},
date = {2026-01-01},
urldate = {2026-06-03},
booktitle = {Optical Fiber Communication Conference (OFC) 2026},
pages = {M3H.2},
publisher = {Optica Publishing Group},
address = {Los Angeles, California},
abstract = {We demonstrate a 940 nm single-mode multi-aperture VCSEL-based optical wireless link achieving
>
80 Gb/s data rates at
<
5 mW optical power, enabling ultra-high-speed, energy-efficient LiFi for next-generation networks.},
keywords = {LiFi, LRDC, optical wireless communication (OWC), vertical-cavity surface-emitting lasers},
pubstate = {published},
tppubtype = {inproceedings}
}
We demonstrate a 940 nm single-mode multi-aperture VCSEL-based optical wireless link achieving
>
80 Gb/s data rates at
<
5 mW optical power, enabling ultra-high-speed, energy-efficient LiFi for next-generation networks.
>
80 Gb/s data rates at
<
5 mW optical power, enabling ultra-high-speed, energy-efficient LiFi for next-generation networks.
4.
Safi, Hossein; Osahon, Isaac N. O.; Tavakkolnia, Iman; Haas, Harald
Ethernet-over-OWC Using VCSELs: Transparent Gigabit Links with Low Latency and Robust Alignment Tolerance Miscellaneous
2026.
Abstract | Links | BibTeX | Tags: FOS: Physical sciences, LRDC, optical wireless communication (OWC), Optics (physics.optics), vertical-cavity surface-emitting lasers
@misc{safi_ethernet-over-owc_2026,
title = {Ethernet-over-OWC Using VCSELs: Transparent Gigabit Links with Low Latency and Robust Alignment Tolerance},
author = {Hossein Safi and Isaac N. O. Osahon and Iman Tavakkolnia and Harald Haas},
url = {https://arxiv.org/abs/2601.13878},
doi = {10.48550/ARXIV.2601.13878},
year = {2026},
date = {2026-01-01},
urldate = {2026-06-03},
publisher = {arXiv},
abstract = {We demonstrate a fully bidirectional 1 Gbs Ethernet over OWC link over a 1m free space path using a VCSEL-PIN pair and only commercially available components. The unamplified, transparent system achieves error-free operation, with a latency of less than 25 ns, and a centimetre-scale alignment tolerance.},
keywords = {FOS: Physical sciences, LRDC, optical wireless communication (OWC), Optics (physics.optics), vertical-cavity surface-emitting lasers},
pubstate = {published},
tppubtype = {misc}
}
We demonstrate a fully bidirectional 1 Gbs Ethernet over OWC link over a 1m free space path using a VCSEL-PIN pair and only commercially available components. The unamplified, transparent system achieves error-free operation, with a latency of less than 25 ns, and a centimetre-scale alignment tolerance.
5.
Osahon, Isaac N. O.; Kostakis, Ioannis; Powell, Denise; Meredith, Wyn; Missous, Mohamed; Haas, Harald; Tang, Jianming; Rajbhandari, Sujan
Neural Network Equalisation for High-Speed Eye-Safe Optical Wireless Communication with 850 nm SM-VCSELs Journal Article
In: Photonics, vol. 11, no. 8, pp. 772, 2024, ISSN: 2304-6732, (Publisher: Multidisciplinary Digital Publishing Institute).
Abstract | Links | BibTeX | Tags: digital equalisation, multilayer perceptron, multilevel pulse amplitude modulation, neural network, optical wireless communications, vertical-cavity surface-emitting lasers
@article{osahon_neural_2024,
title = {Neural Network Equalisation for High-Speed Eye-Safe Optical Wireless Communication with 850 nm SM-VCSELs},
author = {Isaac N. O. Osahon and Ioannis Kostakis and Denise Powell and Wyn Meredith and Mohamed Missous and Harald Haas and Jianming Tang and Sujan Rajbhandari},
url = {https://www.mdpi.com/2304-6732/11/8/772},
doi = {10.3390/photonics11080772},
issn = {2304-6732},
year = {2024},
date = {2024-08-01},
urldate = {2025-10-08},
journal = {Photonics},
volume = {11},
number = {8},
pages = {772},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {In this paper, we experimentally illustrate the effectiveness of neural networks (NNs) as non-linear equalisers for multilevel pulse amplitude modulation (PAM-M) transmission over an optical wireless communication (OWC) link. In our study, we compare the bit-error-rate (BER) performances of two decision feedback equalisers (DFEs)—a multilayer-perceptron-based DFE (MLPDFE), which is the NN equaliser, and a transversal DFE (TRDFE)—under two degrees of non-linear distortion using an eye-safe 850 nm single-mode vertical-cavity surface-emitting laser (SM-VCSEL). Our results consistently show that the MLPDFE delivers superior performance in comparison to the TRDFE, particularly in scenarios involving high non-linear distortion and PAM constellations with eight or more levels. At a forward error correction (FEC) threshold BER of 0.0038, we achieve bit rates of textasciitilde28 Gbps, textasciitilde29 Gbps, textasciitilde22.5 Gbps, and textasciitilde5 Gbps using PAM schemes with 2, 4, 8, and 16 levels, respectively, with the MLPDFE. Comparably, the TRDFE yields bit rates of textasciitilde28 Gbps and textasciitilde29 Gbps with PAM-2 and PAM-4, respectively. Higher PAM levels with the TRDFE result in BERs greater than 0.0038 for bit rates above 2 Gbps. These results highlight the effectiveness of the MLPDFE in optimising the performance of SM-VCSEL-based OWC systems across different modulation schemes and non-linear distortion levels.},
note = {Publisher: Multidisciplinary Digital Publishing Institute},
keywords = {digital equalisation, multilayer perceptron, multilevel pulse amplitude modulation, neural network, optical wireless communications, vertical-cavity surface-emitting lasers},
pubstate = {published},
tppubtype = {article}
}
In this paper, we experimentally illustrate the effectiveness of neural networks (NNs) as non-linear equalisers for multilevel pulse amplitude modulation (PAM-M) transmission over an optical wireless communication (OWC) link. In our study, we compare the bit-error-rate (BER) performances of two decision feedback equalisers (DFEs)—a multilayer-perceptron-based DFE (MLPDFE), which is the NN equaliser, and a transversal DFE (TRDFE)—under two degrees of non-linear distortion using an eye-safe 850 nm single-mode vertical-cavity surface-emitting laser (SM-VCSEL). Our results consistently show that the MLPDFE delivers superior performance in comparison to the TRDFE, particularly in scenarios involving high non-linear distortion and PAM constellations with eight or more levels. At a forward error correction (FEC) threshold BER of 0.0038, we achieve bit rates of textasciitilde28 Gbps, textasciitilde29 Gbps, textasciitilde22.5 Gbps, and textasciitilde5 Gbps using PAM schemes with 2, 4, 8, and 16 levels, respectively, with the MLPDFE. Comparably, the TRDFE yields bit rates of textasciitilde28 Gbps and textasciitilde29 Gbps with PAM-2 and PAM-4, respectively. Higher PAM levels with the TRDFE result in BERs greater than 0.0038 for bit rates above 2 Gbps. These results highlight the effectiveness of the MLPDFE in optimising the performance of SM-VCSEL-based OWC systems across different modulation schemes and non-linear distortion levels.