Laser Stretches 167 Miles

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.

Currently, 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.

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