We all are familiar with LEDs. They can be used for many communication purposes. Billions of visible LEDs are made every year, and therefore the emergence of high brightness AlGaAs and AlInGaP devices has given rise to several new markets. The surprising growth of activity in traditional LED technology has been spurred by the introduction of AlInGaP devices.
The concurrent use of visible LEDs for simultaneous signal and communication, referred to as iLight, results in several new and interesting applications and relies on the concept of quick switching of LEDs and also the modulation visible-light waves for free-space communications. The feasibility of this approach has been examined and hardware has been implemented with experimental results. The use of an optical link has been carried out using an LED traffic-signal head as a transmitter. The light-emitting diode traffic light will be used for either audio or data transmission.
Audio messages are often sent using the LED transmitter, and also the receiver situated at a distance around 20 m away will play back the messages with the speaker. Another prototype that remarks a circular speed-limit sign with a 2-ft diameter was designed. The audio signal are often received in open air over a distance of 59.3 m or 194.5 ft. For information transmission, digital information are often sent using the same LED transmitter, and the experiments were conducted to send a speed limit or location ID info.
The availability of high brightness LEDs create the visible-light medium even more possible for communications. All products with visible-LED parts (like an LED traffic light head) is became an data beacon. This iLight technology has several characteristics that are different from IR. The iLight transceivers uses the direct line-of-sight (LOS) property of visible light. That is right in applications for providing directional guidance to persons with visual impairments.
There are certain advantages for LED over incandescent light. Now let us have a look at these:
- High tolerance to humidity
- Longer life expectancy
- Heat generation is minimum
- Low power consumption
One important characteristic of LEDs is that they’re semiconductor devices capable of quick switching with the addition of acceptable electronics. That is, the visible light emitted by LEDs may be modulated and encoded with audio data for broadcasting.
In addition to their traditional functions as indication and illumination devices, LEDs is used as communication devices for sending and broadcasting audio and digital data. Hence, they will become a part of wireless optical communication systems.
It has long been accomplished that visible light has the potential to be modulated and used as a communication channel with entropy. The application should make use of the directional nature of the communication medium because the receiver needs a LOS to the sound system or transmitter. The locations of the sound signal broadcasting system and the receiver are comparatively stationary. Since the relative speed between the receiver and the supply are much less than the speed of light, the Doppler frequency shift determined by the receiver may be safely neglected. The transmitter will broadcast with viewing angle close to 180.0