An optical antenna that uses a geometrically shaped lens promises to bring greater security to wireless networks for businesses, according to British scientists.

The new device, developed by researchers at the University of Warwick's engineering department, uses a combination of precise curvatures on the lens and a multi-layered filter to achieve its goal.

Optical antennas are already available. But this new antenna is so precise, according to the researchers, that it can detect a signal on a single wavelength of light. The scientists, led by professor Roger Green, assert that the device is 100 times more efficient at gathering in a signal than any previous optical sensor of this kind.

"It's got particular strategic advantages in areas where you want to send large amounts of information quickly or want greater security with lower chances of eavesdropping," Green said.

Wi-Fi, the most common wireless technology today, is hugely popular for creating networks with a radius of about 300 feet for home use and in a few public places such as bookstores, cafes and airports. But the technology, also known as 802.11b, is yet to make an impact on the business world because of fears about security breaches.

Both Wi-Fi and Bluetooth, another wireless standard, use the 2.4GHz band, which most governments around the world have reserved for unregulated use. Because of the way these networks are set up using radio frequencies, it is possible for just about anyone to tap into a network without the knowledge or permission of the people who administer it.

Optical antennas, by contrast, transmit and receive infrared signals, the invisible portion of the electromagnetic spectrum that lies between visible light and radio waves.

The new antenna may have a favourable impact on the use of wireless networks in corporate settings or for business transactions. Compared with radio frequencies, which pass right through walls, infrared beams can be more tightly controlled.

"You make the network more secure because infrared energy is contained within a room and doesn't leak out through the walls and windows. You can equip the windows to reflect infrared energy," said Green. "Also, you can create a tight beam between one point and another which doesn't diverge much in comparison to a radio frequency beam."

Green also noted that the optical technology provides greater bandwidth for businesses and can transfer data over distances of up to three miles. Because the beams can be tightly controlled, Green said, it gives companies the ability to create several wireless networks within one room.

"You can have private and public zones of activity within the same room or wide area," Green said.

The antenna has been licensed to Optical Antenna Solutions, a company based in Nottingham, England. The company plans to develop several commercial uses and will unveil the system at the Comdex trade show in Las Vegas next week.

One of the first ideas under development is for credit card payment systems. The idea is to equip credit cards with infrared links for use at gas pumps and supermarkets, for instance.

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