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Laser Stretches 167 Miles

Photonics.com
Dec 2009
BIRMINGHAM, UK, Dec. 16, 2009 – A 270-km (167.7-mile) optical fiber has been transformed into the world’s longest laser, a platform capable of delivering next-generation, secure information transmission, including telecommunications and broadband.

Fiber.jpgCurrently, telecommunications or data transmissions converted to light to travel through standard optical fibers lose about 5 percent of their power for every kilometer that they travel. The signals must be amplified to ensure they reach their destination, a process that creates background noise and affects signal quality.

The engineers at Aston University in Birmingham, who are leading research into ultralong fiber lasers through the university’s photonics research team, used the Raman effect (a natural phenomenon that affects light passing through a material) and fiber Bragg gratings to create a uniform distribution of light through a cavity in the superlong optical fiber. They also used the laser as a transmission medium, rather than a source of coherent radiation.

Lasers injected light at each end of the fiber, which made the fiber’s atoms give out more energy and emit photons of a longer wavelength. The photons were reflected back into the fiber by special mirrors at each end of the optical link. The fiber then stored a stable, uniform amount of laser light that traveled with the signals and strengthened them, enabling them to move across the fiber at full power without suffering any loss, removing the need to amplify the signals.

The technique also transforms the optical fiber into an ultralong Raman fiber laser that offers new opportunities for handling ultrafast communications at a high operational capacity, the researchers said.

AstonFiber.jpg
Engineers at Aston University in Birmingham, UK, transformed a 270-km (167.7-mile) optical fiber into the world’s longest Raman fiber laser.


Professor Sergei Turitsyn of Aston University’s Photonics Research team believes the 270-km ultralong Raman fiber laser has pushed laser technology to completely new territories. It also increases by a factor of three the research team’s previous record result with a laser of 75 km (46.6 miles), reported in 2006.

“The demands on communication systems are increasing significantly, particularly with the huge growth of Internet traffic. This technology offers a new platform for improving the speed, reliability and the operational capacity of future optical communication systems,” said Turitsyn. “However, even more interesting is a fundamentally new way the laser is used – as a transmission medium, rather than a source of coherent radiation. Despite extraordinary advances in laser science, only recently have the fundamental limits of laser cavity length become an area of exploration. One important new concept here is that an ultralong laser cavity implemented in optical fiber can be seen as a new unique type of a transmission medium. This might lead to a radical new outlook on information transmission and secure communications.”

The Aston team collaborated with the Instituto de Optica in Madrid, Spain, and the Institute of Automation and Electrometry in Novosibirsk, Russia, to achieve the record result, which was published in a recent issue of the journal Physical Review Letters.

For more information, visit: www.aston.ac.uk







GLOSSARY
broadband
Indicating a capability to deal with a relatively wide spectral bandwidth.
coherent radiation
Radiation in which the phase relationship between any two points in the radiation field has a constant difference, or is exactly the same in either the spatial or the temporal mode throughout the duration of the radiation.
light
Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm. In photonic applications light can be considered to cover the nonvisible portion of the spectrum which includes the ultraviolet and the infrared.
optical fiber
A thin filament of drawn or extruded glass or plastic having a central core and a cladding of lower index material to promote total internal reflection (TIR). It may be used singly to transmit pulsed optical signals (communications fiber) or in bundles to transmit light or images.  
photonics
The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
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