Apr. 6, 2010 Besides carrying digital data, optical fibers can also transmit radio signals for wireless communication. So-called "radio-over-fiber" technology has been used to provide access to radio dead zones, but new research is looking into using this technology to broadcast wireless closer to home.
Radio over fiber (RoF) modulates an optical wavelength in the fiber with a radio signal. This solves the attenuation problem during transport of the signal, while allowing the centralization of signal generation and processing equipment. A wireless signal can be simply relayed down the fiber to remote antennas that cost relatively little to install and should be immune to upgrades. RoF is already being used to transmit wireless signals into hard to reach areas like tunnels and stadiums.
In his talk, Mikhail Popov of Acreo AB in Sweden reviews options for taking RoF into homes and buildings along the optical access (PON) infrastructure, as part of a general trend toward merging wired and wireless communication. Fiber in this case would already be carrying Internet traffic, but it could also carry cell phone conversations transmitted over a remote antenna installed in the premises. In a multi-user scenario, the radio signals would pass directly onto the fiber without any processing. However, for a single home, it would make more sense to set up a "femtonode" that converts the radio waves from wireless devices into Internet data and uses the home Internet connection to connect to other mobile users. In any case, this network sharing could provide indoor wireless coverage at a fraction of the cost of relying solely on outdoor base stations, Popov says.
In the future, wireless home networks may be built on an RoF skeleton. As of now, most homes and businesses use WiFi to connect to laptops, but soon TVs and other media devices may need a wireless hook-up. One way to get more bandwidth is to trade WiFi for ultra-wideband (UWB), which can support data rates that are 1,000 times faster. The trouble is that UWB can only travel approximately 10 meters and is unable to penetrate walls, so there needs to be a way to distribute the signal throughout a house or building.
One solution is to use optical fibers. In a separate talk, Benoit Charbonnier of R&D Orange FT Group in France will describe a UWB RoF network that he and his colleagues have built. Their design calls for the UWB signal being transmitted and received by access points in each room. These access points simply relay the wireless signal over the fiber network to a central hub that down-converts the radio frequency to facilitate processing. This network architecture allows all the hardware to be transparent to whatever wireless products are being used in the home. Charbonnier will present recent test results that show his team's RoF network can distribute a 3 Gbit/s signal with good fidelity.
The research is being presented at the Optical Fiber Communication Conference and Exposition/National Fiber Optic Engineers Conference (OFC/NFOEC) -- the world's largest international conference on optical communication and networking -- from March 21-25 at the San Diego Convention Center.
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