CRI听力:Transferring Data via Light

The experiment shows the two laptops transferring data to each other at a speed of 10 megabits per second. There are no cables or wireless router - the data is being transferred by light.

One computer is streaming data for a High Definition video via a normal Ethernet cable to a light. The light switches on and off rapidly and in different patterns.

Below is a receiver, which picks up the light variations and translates it back to normal data. The data is then sent straight to the receiving laptop and the video is displayed on the screen.

The technology has been developed by researchers at the Fraunhofer Heinrich-Hertz Institute in Berlin working together with German Engineering Company Siemens and the French Telecom Company Orange Lab.

Fraunhofer Researcher Dr Jelena Vucic says it is not important what kind of lights are used but the researchers at Fraunhofer have focused on light-emitting diode or LED lights, because they believe it is the "lighting source of the future."

LED lights are small semiconductors that generate light when an electronic current is sent through the device. The lights are increasingly used in homes because of the low energy usage and long lifetime.

Dr Vucic says that to transfer the data a modulator was attached to the LED lights, which made them switch on and off rapidly, much faster than the eye can see.

"The difference between the LED used only for illumination and this that we are doing here is that we are adding a very fast flickering, or intensity variation, to this LED in order to transmit data. And, this is much much faster than the common eye can see so there is no difference to the common viewer."

The experiment shown here is sending a high definition video with a 10 megabyte per second connection, already faster than most people would experience with a standard wireless Internet connection at home.

But according to Dr Vucic the speed could be increased dramatically.

"There are some speeds from for example 10 megabits per second to up to 800 megabits per second so almost a gigabyte per second is imaginable. "

But with Wi-Fi Internet - transmitted via radio waves - already widely available, why is there the need for an alternative? According to Dr. Anagnostis Paraskevopoulos Visible Light Communications is not intended to replace Wi-Fi.

"We are not fighting against Wi-Fi as a matter of fact. We know that this technology has some advantages but also some drawbacks."

One such drawback is limitations to where Wi-Fi radio waves can be used. For example, many hospitals don't allow Wi-Fi Internet in areas where is could interfere with sensitive equipment.

The researchers at Fraunhofer hope that within a few years all such areas will be connected wirelessly with Visible Light Communications technology.

Operation theatres could be connected, and wireless surgical robots could be handled from a distance, or X-Ray images could be transmitted instantly.

Another drawback with Wi-Fi, according to Dr Paraskevopoulos, is the lack of security when important data is transmitted over radio waves.

"Your data can be very easily spied, hacked, because radio waves can go through walls. So, light is very easy to isolate, you just need rice paper and your data is not being hacked."

But the line of sight transmission is also a drawback. When the light is interrupted, such as when someone shades the receiver with the hand, the data transfer is immediately interrupted. When the hand is removed the data transfer continues.

For CRI, I am Li Dong.