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Monday, March 08, 2010

Light better than radio waves for wireless AND everyone may see the light

Optical transmission is key to secure and rapid indoor communications

WASHINGTON, USA: Light is better than radio waves when it comes to some wireless communications, a new study has found.

Optical communications systems could provide faster, more secure communications with wider bandwidth and would be suitable for restricted areas like hospitals, aircraft and factories.

Sending information via light waves either in physical light guides or wirelessly is not new, but existing wireless systems either require direct line of sight or are diffused and have low signal strength.

Penn State University (PSU) engineers chose to take a different approach using multi-element transmitters and multi-branch optical receivers in a quasi-diffuse configuration.

The system uses a high-powered laser diode - a device that converts electricity into light - as the optical transmitter and an avalanche photo diode, a device that converts light to electricity, as the receiver. The light bounces off the walls and is picked up by the receiver.

"Unless the walls are painted solid black, there is no need to worry about transmission within a room," said Jarir Fadlullah, PSU graduate student in electrical engineering.

The researchers tested infrared light, but the system will also work with visible light and ultraviolet light.

"The optical system we have offers a very large bandwidth thus a very high speed," said Fadlullah. "We can send one gigabit per second or more over a gigahertz band."

The researchers, including Mohshen Kavehrad, PSU professor of electrical engineering, think this looks like an ideal system.

Radio frequency systems do not require line of sight transmission, but can pass through some substances and so present a security problem, said a release.

The study was presented Wednesday at SPIE Phonotics West Conference in San Francisco.

SOURCE http://www.ciol.com/




At 8:33 AM, Blogger 無尾熊可愛 said...

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