For more than six years, a team of engineers from Cnet, the research and development arm of France Telecom, have been working on soliton technologies for long-haul communications. One product of the team's labors is the formation a new company called Algety Telecom (Lannion, France), which plans to bring soliton dense wavelength-division multiplexing (DWDM) systems, a new breed of optical transmission equipment, to market by mid-2000.
Cnet is responsible for numerous pioneering developments in soliton technology, including the current record for terrestrial soliton transmission of 1 Tbit/sec over a distance of 1000 km. Algety, incorporated in France during the second quarter of 1999, negotiated with Cnet to gain the technology, patents, and know-how necessary to continue the advancement of soliton communications.
Algety is developing a new generation of solitons for DWDM and Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) long-haul transmission. The company's objective is to enable carriers to increase the distance between regeneration and amplification sites and improve the overall spectral efficiency of their networks. According to Algety, carriers could eliminate millions of dollars in equipment from every link, decreasing long-haul costs typically by a factor of two or even three.
"With traditional techniques, you have to regenerate the signal every 300 to 400 km," says Jerome Faul, managing director at Algety. "With solitons, you only have to regenerate every 1000 to 2000 km. So you can increase the distance between two regenerators and save a lot of money. It's perfectly suited for large countries such as the United States, where you have miles and miles between cities. It's a technology designed for long-haul--the longer, the better."
A soliton is a natural phenomenon dating back to 1834, when Scotland's John Scott Russel made an observation while riding horseback along a canal. Russel noticed that after a barge had come to a sudden halt, a big solitary wave continued to travel without any apparent shape deformation or speed variation. He followed the wave more than 6 mi and reported his observation in 1844. Some 60 years later, mathematicians were able to unravel much of the mystery behind the phenomenon.
By 1973, Bell Laboratories (Murray Hill, NJ) discovered that solitons could be produced in optical fiber by sufficiently intense pulses of light and that the phenomenon could overcome the problem of dispersion (or the spreading of a light pulse). This discovery led to a renewed interest in solitons as a means to increase transmission distances and bandwidth capacity--until DWDM reared its head in the telecommunications realm.
Since the mid-'80s, the development of DWDM technology has relegated soliton transmission research to a lower profile. But as limitations in DWDM transmission have appeared, researchers--particularly in Europe--have continued to work on perfecting soliton technology.
Algety has embraced DWDM technology to combine the best of both worlds. The company plans to introduce products incorporating advanced DWDM technology to maximize available fiber bandwidth and soliton technology to increase the speed per channel.
"Our products will include high-speed multiplexers," says Faul. "Each input is shaped like a soliton and multiplexed with all the different inputs to send on a single fiber. This is where we can achieve the high capacities. DWDM technology is new in the soliton arena, and up to now, nobody else has successfully mixed soliton technology and DWDM technology."
According to Faul, carriers can keep their existing fiber-network infrastructure and merely change equipment at the ends of the fiber. Moving to higher capacities with traditional methods has meant that carriers had to reduce transmission distances between regenerators.
"[Soliton transmission] allows them to keep their existing infrastructure and replace their old equipment with ours," says Faul. "So in the same step, they can upgrade the network in terms of capacity and keep the infrastructure in terms of transmission distance. There are also physical problems, such as dispersion, in some existing fibers that occur when increasing capacities. A key feature of the new soliton products will be the ability to manage those problems very well."
Algety plans to have prototype products available for testing in the laboratories by year-end.