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Data Transmission through Visible Light
Other Information conveyed through electric field, signal is complex valued and bipolar unlike VLC which sends information through light, is real valued and unipolar. Visible Light Communication (VLC) Visible light is the form in which electromagnetic radiation with wave lengths in a particular range is interpreted by the human brain. Visible light is thus by dentition comprised of visually-perceivable electromagnetic waves. The visible spectrum covers wave lengths from 380 nm to 750 nm shows for each wave length the associated colour tone as perceived byhuman beings. This is 10000 times that of radio spectrum. Edinburgh start-up Visible Light Communications (VLC) is focussing on using flickering LEDs instead of Wi-Fi for broadband communications. Speeds of up to 800Mbits/sec have been achieved for the technology, called Li-Fi, but the first product from VLC - a consumer transmitter - will deliver data at 100Mbits/sec using VLC's SIM-OFDM technology and optical spatial modulation. The technology was invented by Edinburgh University's Harald Haas. This emerging technology provides optical wireless Communication (OLC) by using visible light. Today it is seen as an alternative to different RF-based communication services in wireless personal-area-networks. An additional opportunity is arising by using current state-ofthe-art LED lighting solutions for illumination and communication at the same time and with the same modulethis can be done due to the abilityto module LEDs at speeds for faster than the human eye can detect while still providing artificial lightning.
Figure 2
Basic Block Diagram Technologies used Visible light communication (VLC) is a fascinating and emerging communication technology employing visible light with spectrum between 400 THz and 790 THz for both illumination and data communication. Signal is transmitted with LED (about 10 Mbps) by their intensity modulations. Several modulation techniques could be adopted e.g. on/off keying (OOK) which is the main output for the system. The VLC uses LEDs to send data by flashing light at undetectable