The USA's The Defence Advanced Research Projects Agency (DARPA) is claiming to have developed a hollow optical fibre that can transmit data 30 per cent faster than conventional broadband fibre. DARPA says the design, which uses a hollow, air-filled core, improves performance by forcing light to travel through channels of air, instead of the glass around it. It says the spider-web-like, hollow-core fibre is the first to demonstrate single-spatial-mode, low-loss and polarisation control, which are key properties needed for advanced military applications such as high-precision fibre-optic gyroscopes for inertial navigation. DARPA-funded researchers led by Honeywell International developed the technology. The hollow-core fibre is the first to include three critical performance-enabling properties, DARPA says: Single-spatial-mode: light can take only a single path, enabling higher bandwidth over longer distances; Low-loss: light maintains intensity over longer distances; and Polarisation control: the orientation of the light waves is fixed in the fibre, which is necessary for applications such as sensing, interferometry and secure communications. Hollow-core fibre can also be bent and coiled while guiding light at speeds 30 percent faster than conventional fibre. 'Previous instantiations of hollow-core fibre have shown these high propagation speeds, but they weren't able to do so in combination with the properties that make it useful for military applications,' said Josh Conway, DARPA program manager. 'The real breakthrough with COUGAR fibre is that it can achieve a single-spatial-mode, maintain polarisation and provide low loss, all while keeping more than 99 percent of the optical beam in the air.'
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