Air-filled fibres could speed up the Web

The Internet has created a boom in long-distance optical communications. Web surfers click away and download ever-larger files, oblivious to their distance from a Web host. As a result the demand for capacity in undersea optical-fibre communications is escalating. A simple way to increase the capacity is to send many separate optical wavelengths through the same fibre, a technique known as wavelength division multiplexing. However, there is a limit to the optical power that can be used to send information along a fibre, and this – rather than the bandwidth of the fibre, which is prodigious – limits the capacity of optical fibres to carry information.