Visible light communication
Visible light communication (VLC) is a data communications medium using visible light between 400 and 800 THz (780–375 nm). Using visible light is less dangerous for high-power applications because humans can perceive it and act to protect their eyes from damage.
The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s. Low rate[vague] data transmissions at 1 and 2 kilometres (0.6 and 1.2 mi) were demonstrated. RONJA achieves full Ethernet speed (10 Mbit/s) over the same distance thanks to larger optics and more powerful LEDs.
Specially designed electronic devices generally containing a photodiode receive signals from such light sources, although in some cases a cell phone camera or a digital camera will be sufficient. The image sensor used in these devices is in fact an array of photodiodes (pixels) and in some applications its use may be preferred over a single photodiode. Such a sensor may provide either multi-channel communication (down to 1 pixel = 1 channel) or a spatial awareness of multiple light sources.
VLC can be used as a communications medium for ubiquitous computing, because light-producing devices (such as indoor/outdoor lamps, TVs, traffic signs, commercial displays, car headlights/taillights, etc.) are used everywhere.
The history of Visible Light Communications (VLC) dates back to 1880 in Washington, D.C. when the Scottish-born scientist Alexander Graham Bell invented the photophone, which transmitted speech on modulated sunlight over several hundred meters. It is interesting to note that this actually pre-dates the transmission of speech via radio.
More recently the Nakagawa Laboratory, in Keio University, Japan began work in 2003 using LEDs to transmit data by visible light. Since then there have been numerous research activities focussed on VLC. The notable research activities being Smart Lighting Engineering Centre, Omega Project, COWA, ByteLight, Inc.D-Light Project, UC-Light Centre and work at Oxford University.
In 2006, researchers from CICTR at Penn State proposed a combination of power line communication (PLC) and white light LED to provide broadband access for indoor applications. This research suggested that VLC could be deployed as a perfect last-mile solution in future.
In January 2010 a team of researchers from Siemens and Fraunhofer Institute for Telecommunications (Heinrich Hertz Institute in Berlin) demonstrated transmission at 500 Mbit/s with a white LED over a distance of 5 metres (16 ft), and 100 Mbit/s over longer distance using five LEDs.
The VLC standardization process is conducted within IEEE Wireless Personal Area Networks working group (802.15).
Recently, VLC-based indoor positioning system has become an attractive topic. Publications have been coming from Nakagawa Laboratory, COWA at Penn State and other researchers around the world.
Another recent application is in the world of toys, thanks to cost-efficient and low-complexity implementation, which only requires one microcontroller and one LED as optical front-end 
- Fiber-optic communication
- Free space optics
- IrDA — Same principle as VLC but uses infrared light instead of visible light
- "Image Sensor Communication". VLC Consortium.[dead link]
- "Lighthouse Sub Project". VLC Consortium.[dead link]
- "About Visible Light Communication". VLC Consortium.[dead link]
- "Intelligent Transport System – Visible Light Communication". VLC Consortium.[dead link]
- M. Kavehrad, P. Amirshahi, “Hybrid MV-LV Power Lines and White Light Emitting Diodes for Triple-Play Broadband Access Communications,” IEC Comprehensive Report on Achieving the Triple Play: Technologies and Business Models for Success, ISBN 1-931695-51-2, pp. 167-178, January 2006. See publication here
- "500 Megabits/Second with White LED Light" (Press release). Siemens. Jan 18, 2010.
- "St. Cloud first to sign on for new technology" (Press release). St. Cloud Times. Nov 19, 2010.
- Yoshino, M.; Haruyama, S.; Nakagawa, M.; , "High-accuracy positioning system using visible LED lights and image sensor," Radio and Wireless Symposium, 2008 IEEE , vol., no., pp.439-442, 22-24 Jan. 2008. See publication here
- S. Horikawa, T. Komine, S. Haruyama and M. Nakagawa,”Pervasive Visible Light Positioning System using White LED Lighting”, IEICE, CAS2003-142,2003.
- Zhang, W.; Kavehrad, M.; , "A 2-D indoor localization system based on visible light LED," Photonics Society Summer Topical Meeting Series, 2012 IEEE , vol., no., pp.80-81, 9–11 July 2012. See publication here
- Lee, Yong Up; Kavehrad, Mohsen; , "Long-range indoor hybrid localization system design with visible light communications and wireless network," Photonics Society Summer Topical Meeting Series, 2012 IEEE , vol., no., pp.82-83, 9–11 July 2012. See publication here
- Panta, K.; Armstrong, J.; , "Indoor localisation using white LEDs," Electronics Letters. vol.48, no.4, pp.228-230, February 16, 2012.See publication here
- Hyun-Seung Kim; Deok-Rae Kim; Se-Hoon Yang; Yong-Hwan Son; Sang-Kook Han; , "Indoor positioning system based on carrier allocation visible light communication," Quantum Electronics Conference & Lasers and Electro-Optics (CLEO/IQEC/PACIFIC RIM), 2011 , vol., no., pp.787-789, Aug. 28 2011-Sept. 1 2011. See publication here
- Giustiniano D.; Tippenhauer N. O.; Mangold, S.; , "Low-Complexity Visible Light Networking with LED-to-LED Communication" Wireless Days, 2012 IFIP, (pp. 1-8), 21-23 Nov. 2012., Best Paper Award See publication here
- IEEE 802.15 WPAN Task Group 7 (TG7) Visible Light Communication