United States: Fibreless fibre optics developed by US Air Force.Byline: datta03 US Air Force boffins say they have created wireless links of similar capacity and quality to optical fibre, allowing extremely high mobile bandwidth and - perhaps - the use of quantum encryption See quantum cryptography. methods without a physical connection. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. an announcement issued earlier this week by the US Air Force Office of Scientific Research, the Office's Dr David Hughes
The idea is to use a laser beam through the air to carry information optically in the same way that sending light down fibre works. In the case of fibre, it's possible to send information - for instance encryption keys - coded as individual photons, quanta quan·ta n. Plural of quantum. of light. Any attempt to intercept such info would by definition involve changing it, meaning that any eavesdropping Secretly gaining unauthorized access to confidential communications. Examples include listening to radio transmissions or using laser interferometers to reconstitute conversations by reflecting laser beams off windows that are vibrating in synchrony to the sound in the room. would surely be detected. Thus quantum methods might offer better security. But for this to work, a very clear signal is needed. Light travelling down a fibre offers such a signal, but normally light travelling through the erratic medium of air would not. "When you transmit information through turbulence (motion in the atmosphere caused by turbulent cells or "wind") it's distorted just like the information coming from the light reflected off a distant, twinkling star to your eye. It's fuzzy," says Hughes. "You have to overcome that by using adaptive optics to rectify the distortion and get a better quality signal." Astronomers cheesed off by twinkly stars use adaptive optics, which measure distortion of an incoming photon stream very fast and use piezoelectric The property of certain crystals that causes them to produce voltage when a mechanical pressure is applied to them such as sound vibrations. This technique is used to build crystal microphones, phonograph cartridges and strain gauges, all of which turn mechanical movement into voltage. actuators to warp the shape of a telescope mirror to tolerances of one fifty-thousandth of a millimetre every millisecond One thousandth of a second. See space/time and ohnosecond. (unit) millisecond - (ms) One thousandth of a second, one thousand microseconds. A long time for a modern computer. . This lets the mirror produce an image approaching theoretical perfect performance - the sort of performance you need to start dealing in in quanta/photons. Hughes and his fellow air force boffins report that they have used lasers with adaptive optics to set up 35-km long laser links "without distortions" in "both stationary and flight situations". "It wouldn't take much to apply the technology to operational aircraft for the Air Force," says Hughes. Apart from the possibility of quantum crypto methods, distortion-free laser links would offer very high bandwidth just as fibres do - which might be at least as useful as exotic security methods. This is especially true given the massive bandwidth hunger and spectrum overcrowding overcrowding overcrowding of animal accommodation. Many countries now publish codes of practice which define what the appropriate volumetric allowances should be for each species of animal when they are housed indoors. Breaches of these codes is overcrowding. seen in modern wars - and, increasingly, modern cities. Copyright : Euclid Infotech Pvt. Ltd. Provided by Syndigate.info an Albawaba.com company |
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