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US navy seeks ‘dial-a-blast’ bomb
TECHNOLOGY
Immortal signals promise future of perfect video University of Southampton, UK. However, light signals are gradually distorted by interacting with the fibre – a process known as attenuation. The more complex the signal, the harder it becomes to resolve after attenuation. What is needed is a way to reverse the degradation process and recreate the original signal, says Richardson, and his
US navy seeks ‘safer’ bomb to reduce civilian casualties COULD a variable-yield bomb reduce the number of innocent people killed or injured during an air attack targeting enemy soldiers? That’s the thinking behind a US navy plan to develop a “dial-a-blast” bomb. The navy is seeking proposals from companies to create a bomb weighing 200 kilograms that can either be detonated at full or reduced power. The idea is that the device could be loaded onto planes before a target has been identified, and the explosive power set by the pilot once a target is known. If there is a risk of killing civilians, then the explosive power can be reduced to ensure a small 26 | NewScientist | 11 September 2010
The team has demonstrated the technique on signals at 40 gigabits per second, but Richardson says it should handle higher data rates too (Nature Photonics, DOI: 10.1038/nphoton.2010.203). Similar systems have been demonstrated before, but only in a “very controlled way where the phase and carrier frequency of the incoming signal are known”, says Richardson. The new device can reconstruct an incoming signal without this information – a more likely scenario in the real world. The current version works with relatively simple signals where the information is encoded into one of two light phases – so called “binary phase-shifted keys” (PSK). “Our primary interest is in extending the approach to work with more complex signals such as quadrature PSK”, which can encode more data in the phase, says Richardson. A team led by Guifang Li at the University of Central Florida in Orlando has demonstrated components of the device separately, but not combined them into a fully functioning system. “The results they demonstrated are quite –Light that never fades– impressive,” he says. Colin Barras n JOHN RENSTEN/CORBIS
A PERFECT stream of video delivered down your broadband connection without irritating blips may seem as likely as uncovering the elixir of youth. Now a team of optical engineers think they have discovered the secret to both. They’ve devised a way to revitalise light signals being sent down optical fibres, enabling them to send more information down the wires. Bandwidth-hungry video streaming applications are prompting changes in the way that information is sent across the internet via its network of optical fibres. Conventionally, data is sent as a series of on-off light pulses, where each pulse encodes a single bit of information. More data can potentially be squeezed onto a stream of light by modifying the phase of each light pulse in a measurable way. Even greater carrying capacity can be achieved using light at several intensity levels, potentially “an order of magnitude” higher than now, says David Richardson at the
team has now developed one. Their device makes a copy of the attenuated incoming signal, and “mixes” it with a laser beam in a length of specially designed optical fibre. This generates two additional strong signals that are perfectly in phase with the data signal, one with a frequency just higher than the original and one with a frequency just lower. These signals can then act as a scaffold that, after interaction with a second copy of the data signal in a second fibre, removes the noise and generates a pristine version.
blast radius. In an unpopulated area the bomb, currently known as the Selectable Output Weapon, could be set so that it has the same power as a regular bomb of the same size. Carrying a single bomb would make it easier and cheaper for the navy to arm its planes. The navy plans to invest $9.9 million over the next five years in developing the bomb once it has accepted a proposal. One company vying for the funding is ATK, a defence manufacturer based in Plymouth, Minnesota, which claims to have technology that could do the job. ATK’s approach is based on the
principle that explosives can burn in two different ways. One is via detonation, in which the flame front moves at supersonic speed and produces a powerful blast. The other is deflagration, or subsonic burning, which causes little or no blast. In ATK’s design the explosive can be ignited at both ends, one set to produce a detonation, the other
“The risk of hitting the wrong target is higher than that of the pilot setting the wrong bomb yield” deflagration. By varying the timing of these two ignitions, the proportion of explosive consumed by detonation can be altered in a controlled manner. ATK says it has already demonstrated a 27-kilogram bomb
with three different power modes. As well as full-power mode, the bomb has a reduced power mode which reduces the size of the blast area by 40 per cent. There is also a deflagration-only mode, which ATK claims left a mirror located less than 2 metres away unscathed during tests. While such a device should help minimise civilian casualties, it will place a burden on the pilot to get the setting right, says John Pike, a defence analyst with Washington DC think tank GlobalSecurity.org. “There is always the risk of selecting the wrong yield.” However the risk of hitting the wrong target may be greater. The big advantage for the military is that it would allow aircraft to “take off without knowing what sort of targets will be attacked”, Pike says. David Hambling n
Immortal signals promise future of perfect video University of Southampton, UK. However, light signals are gradually distorted by interacting with the fibre – a process known as attenuation. The more complex the signal, the harder it becomes to resolve after attenuation. What is needed is a way to reverse the degradation process and recreate the original signal, says Richardson, and his
US navy seeks ‘safer’ bomb to reduce civilian casualties COULD a variable-yield bomb reduce the number of innocent people killed or injured during an air attack targeting enemy soldiers? That’s the thinking behind a US navy plan to develop a “dial-a-blast” bomb. The navy is seeking proposals from companies to create a bomb weighing 200 kilograms that can either be detonated at full or reduced power. The idea is that the device could be loaded onto planes before a target has been identified, and the explosive power set by the pilot once a target is known. If there is a risk of killing civilians, then the explosive power can be reduced to ensure a small 26 | NewScientist | 11 September 2010
The team has demonstrated the technique on signals at 40 gigabits per second, but Richardson says it should handle higher data rates too (Nature Photonics, DOI: 10.1038/nphoton.2010.203). Similar systems have been demonstrated before, but only in a “very controlled way where the phase and carrier frequency of the incoming signal are known”, says Richardson. The new device can reconstruct an incoming signal without this information – a more likely scenario in the real world. The current version works with relatively simple signals where the information is encoded into one of two light phases – so called “binary phase-shifted keys” (PSK). “Our primary interest is in extending the approach to work with more complex signals such as quadrature PSK”, which can encode more data in the phase, says Richardson. A team led by Guifang Li at the University of Central Florida in Orlando has demonstrated components of the device separately, but not combined them into a fully functioning system. “The results they demonstrated are quite –Light that never fades– impressive,” he says. Colin Barras n JOHN RENSTEN/CORBIS
A PERFECT stream of video delivered down your broadband connection without irritating blips may seem as likely as uncovering the elixir of youth. Now a team of optical engineers think they have discovered the secret to both. They’ve devised a way to revitalise light signals being sent down optical fibres, enabling them to send more information down the wires. Bandwidth-hungry video streaming applications are prompting changes in the way that information is sent across the internet via its network of optical fibres. Conventionally, data is sent as a series of on-off light pulses, where each pulse encodes a single bit of information. More data can potentially be squeezed onto a stream of light by modifying the phase of each light pulse in a measurable way. Even greater carrying capacity can be achieved using light at several intensity levels, potentially “an order of magnitude” higher than now, says David Richardson at the
team has now developed one. Their device makes a copy of the attenuated incoming signal, and “mixes” it with a laser beam in a length of specially designed optical fibre. This generates two additional strong signals that are perfectly in phase with the data signal, one with a frequency just higher than the original and one with a frequency just lower. These signals can then act as a scaffold that, after interaction with a second copy of the data signal in a second fibre, removes the noise and generates a pristine version.
blast radius. In an unpopulated area the bomb, currently known as the Selectable Output Weapon, could be set so that it has the same power as a regular bomb of the same size. Carrying a single bomb would make it easier and cheaper for the navy to arm its planes. The navy plans to invest $9.9 million over the next five years in developing the bomb once it has accepted a proposal. One company vying for the funding is ATK, a defence manufacturer based in Plymouth, Minnesota, which claims to have technology that could do the job. ATK’s approach is based on the
principle that explosives can burn in two different ways. One is via detonation, in which the flame front moves at supersonic speed and produces a powerful blast. The other is deflagration, or subsonic burning, which causes little or no blast. In ATK’s design the explosive can be ignited at both ends, one set to produce a detonation, the other
“The risk of hitting the wrong target is higher than that of the pilot setting the wrong bomb yield” deflagration. By varying the timing of these two ignitions, the proportion of explosive consumed by detonation can be altered in a controlled manner. ATK says it has already demonstrated a 27-kilogram bomb
with three different power modes. As well as full-power mode, the bomb has a reduced power mode which reduces the size of the blast area by 40 per cent. There is also a deflagration-only mode, which ATK claims left a mirror located less than 2 metres away unscathed during tests. While such a device should help minimise civilian casualties, it will place a burden on the pilot to get the setting right, says John Pike, a defence analyst with Washington DC think tank GlobalSecurity.org. “There is always the risk of selecting the wrong yield.” However the risk of hitting the wrong target may be greater. The big advantage for the military is that it would allow aircraft to “take off without knowing what sort of targets will be attacked”, Pike says. David Hambling n