Visible Light Communication (VLC) is a data communications medium using visible light between 400 THz (780 nm) and 800 THz (375 nm). Visible light is not injurious to vision. Low-cost wireless communication network can be created using Visible Light Communication system. Visible Light Communication is a potential solution to the shortage of global wireless radio spectrum. Visible Light Communication 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. Visible Light Communication can be seen by the human eye, carry an embedded signal, which is unseen.

Visible Light Communication technology uses ordinary lamps (not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s. Low rate data transmissions at 1 kilometre (0.6 mi) and 2 kilometres (1.2 mi) were demonstrated and achieved full Ethernet speed (10 Mbit/s) using powerful LEDs and laser optics.

Visible Light Communication SystemLED lights are more powerfull in interior lighting and suitable for Visible Light Communication System. This switching occurs at ultra-high speeds, so far beyond what the human eye can detect, that the light appears to be constantly on. Amazingly, the technology can transmit a signal even when the light appears off. These embedded signals are emitted from the LEDs in the form of binary code; ‘off’ equals zero and ‘on’ equals one.

Newer forms of LEDs, known as RGBs (red, green and blue), have three separate LEDs that, when lit at the same time, emit a light that is perceived to be white. As these involve no delay in stimulating a phosphor, data rates in RGBs can reach up to 100Mb/sec. Resonant-cavity LEDs (RCLEDs), which are similar to RGB LEDs and are fitted with reflectors for spectral clarity, can now work at even higher frequencies.

Possible Applications of Visible Light Communication

  • In-door and outdoor wireless communication for personal gadgets, and for broadband internet.
  • One of the most promising applications is in car-to-car communication. If the headlights on a car could communicate with the tail lights of the car ahead, VLC collision-avoidance technology would be hugely significant in the automotive industry.
  • Traffic lights could send detailed information of congestion up ahead directly to a vehicle.
  • Smart lighting for buildings with VLC provides the infrastructure for illumination, control and communications and will greatly reduce wiring and energy consumption within a building.
  • Hospitals & Healthcare: There are advantages for using VLC in hospitals and in healthcare. Mobile phones and WiFi’s are undesirable in certain parts of hospitals, especially around MRI scanners and in operating theatres.
  • Underwater Communication: RF does not work underwater but visible light can support high speed data transmission over short distances in this environment. This could enable divers and underwater vehicles to talk to each other.
  • Aviation: Radio is undesirable in passenger compartments of aircraft. LEDs are already used for illumination and can also be used instead of wires to provide media services to passengers.
  • Wireless Mobile Connectivity: Visible light communication provides a much higher data transfer rate than Bluetooth or WiFi.

In 2011, Siemens and Berlin’s Heinrich Hertz Institute achieved a data-transfer rate of 500Mb/sec with a white LED, beating their earlier record of 200Mb/sec. As LED technology improves with each year, VLC is coming closer to reality and engineers are now turning their attention to its potential applications. But, to be successful, VLC has to prove itself against competing technologies of Lidar, Radar and RF, as well as to overcome some of its own technical challenges.