# A Review-Unguided Optical Communications: Developments, Technology Evolution, and Challenges
## 5 Advancements in Optical Wireless Communications
### Visible Light Communication (VLC)
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No** & **Li-Fi System Manufacturer** & **Web Link** \\ \hline
1 & M/s Pure Li-Fi & www.purelifi.com \\
2 & Olecdcomm & www.olcedomm.com \\
3 & Li-Fi & [[https://lifio.co/](https://lifio.co/)]([https://lifio.co/](https://lifio.co/)) \\
4 & Global Li-Fi & [[http://globaliffetch.com/](http://globaliffetch.com/)]([http://globaliffetch.com/](http://globaliffetch.com/)) \\
5 & Lifx & [[https://www.lifx.com/](https://www.lifx.com/)]([https://www.lifx.com/](https://www.lifx.com/)) \\
6 & LVX & [[http://www.lvx-system.com/](http://www.lvx-system.com/)]([http://www.lvx-system.com/](http://www.lvx-system.com/)) \\
7 & Wipro & [[https://www.wipro.com/](https://www.wipro.com/)]([https://www.wipro.com/](https://www.wipro.com/)) \\
8 & M/s Basic6 & [[http://www.basic6.com/](http://www.basic6.com/)]([http://www.basic6.com/](http://www.basic6.com/)) \\
9 & Firefly Li-Fi & www.fireflylifi.com \\
10 & Velmemi & www.velmemi.com \\
11 & VLNcomm & www.vlncomm.com \\
12 & Lumefficient & [[https://lumefficient.com/](https://lumefficient.com/)]([https://lumefficient.com/](https://lumefficient.com/)) \\
13 & Signify & www.signify.com \\
14 & General Electric & [[https://www.ge.com/](https://www.ge.com/)]([https://www.ge.com/](https://www.ge.com/)) \\
15 & Koninklijke Philips N.V. & [[https://www.philips.com/global](https://www.philips.com/global)]([https://www.philips.com/global](https://www.philips.com/global)) \\
16 & Panasonic Corporation & [[https://www.panasonic.com/global/home.html](https://www.panasonic.com/global/home.html)]([https://www.panasonic.com/global/home.html](https://www.panasonic.com/global/home.html)) \\
17 & Acuity Brands Inc. & [[https://www.acuitybrands.com/](https://www.acuitybrands.com/)]([https://www.acuitybrands.com/](https://www.acuitybrands.com/)) \\
18 & Light Pointe Communications Inc. & [[https://www.lightpointe.com/](https://www.lightpointe.com/)]([https://www.lightpointe.com/](https://www.lightpointe.com/)) \\
19 & Fsona Networks & [[http://www.fsona.com/](http://www.fsona.com/)]([http://www.fsona.com/](http://www.fsona.com/)) \\
20 & Infinity Technology Services & [[https://www.infinitygroupcorp.com/](https://www.infinitygroupcorp.com/)]([https://www.infinitygroupcorp.com/](https://www.infinitygroupcorp.com/)) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of Li-Fi system manufacturers (All accessed on 15 January 2023). recognized and approved VLC technology as a standard: 802.15.7 [264; 265]. The overview of VLC and how it is useful in mobile networking and sensing applications are described in [266]. The author of [267] investigated a VLC-based indoor positioning systems using a variety of techniques including statistical, optimization, and sensor-assisted approaches. Furthermore, in the simulation and experiment, the accuracy of IPS based on VLC is covered. VLC-based positioning systems and their applications in indoor and outdoor environments are studied in [268]. In addition, therein, the various algorithms used in the positioning methods are categorized. VLC network architecture and optimization techniques using the user-centric (UC) design theory for the 5G/6G era are studied in [269]. In [270], the authors briefed the optimization of VLC networks for NOMA, security issues, AP coordination, user-to-AP association, resource and power allocation, simultaneous information transmission, and energy harvesting. Furthermore, the authors also examined VLC energy harvesting, VLC networks' physical layer protection strategies, and hybrid VLC/RF networks. The authors of [271] described VLC in terms of its physical characteristics, architecture, applications, problems, recent research platforms, and system design viewpoint. In [272], the authors addressed various challenges in future communications and proposed different hybrid optical-to-optical and RF-to-optical wireless systems for the IoT and 5G/6G (and beyond) technologies. A VLC system uses the IM/DD process, which is commonly used in the implementation of WOC systems.