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To: Kenneth E. Phillipps who wrote (15298)	7/6/2000 11:46:39 AM
From: Bill	Respond to of 21876

Here's a good explanation of soliton technology from one of the trade rags. The concept is more than 150 years old, but it could revolutionize optical networks. Although not without controversy, some vendors are looking to solitons to build the next generation of dense wavelength division multiplexers (DWDM) that can operate over longer distances and provide higher-capacity channels. Solitons are pulses of light that keep their shape even after colliding with one another. This phenomenon was first observed by a Scotsman, John Scott Russell, as he rode alongside a barge in a canal in Edinburgh. As the barge came to halt, he noticed that a large solitary wave, after colliding with other waves, continued for several miles without losing its shape. Although work with solitons began a quarter-century ago at Bell Labs, advances in DWDM technology have overshadowed this research. Now some companies such as French start-up Algety Telecom are convinced soliton DWDM systems will solve the problem of chromatic dispersion, or the broadening of a pulse of light, in DWDM networks. Algety, which has its roots in CNET--France Telecom’s R&D unit that is credited with being the first to transmit 1 Tbps over 1000 km using soliton technology--plans to have a beta version of a soliton-based DWDM system before the end of the year. The company is particularly interested in the U.S. market and will soon be establishing an office in the States. According to Jereme Faul, Algety’s vice president of software strategy and development, while there might be some debate over whether solitons are necessary for 10-Gbps wavelengths, 40-Gbps and higher wavelengths demand the use of solitons. However, officials at Cisco Optical Networking Group (formerly Pirelli Optical Systems), have rejected solitons for high-rate systems, although MCI conducted a successful trial in 1998 using Pirelli’s soliton-based DWDM systems that transmitted four data streams at 10 Gbps each. Stuart Woods, North American product marketing manager for the Cisco group, noted that soliton uses the return-to-zero (RZ) modulation format, whereas network devices such as routers, ATM switches and SONET equipment are based on the nonreturn-to-zero (NRZ) scheme. “Once you go down the path of RZ, you’re automatically closing yourself to being interoperable,” he said. According to Woods, neither distance nor faster channel speeds require the use of RZ. Moreover, a move to 25-GHz channel spacing cannot be done with solitons because a soliton has wide pulse. According to Woods, what exist today are not true solitons but dispersion-managed solitons that require properties in the fiber to tweak the pulse so it holds its shape. “Dispersion-managed soliton is what we used in the trial [at MCI],” he said. Rick Barry, chief technology officer for Sycamore, takes issue with such criticism. Barry said that there is “overwhelming agreement” that dispersion-managed soliton is the choice technology for next-gen, ultralong-haul, terrestrial systems. Addressing the objection to the RZ format, Barry said: “Most routers use NRZ because NRZ is simpler and routers were not designed or required to transmit ultralong-haul distances. The interface between the routers and WDM system will convert the NRZ format to the RZ format. This [approach] separates the design of the routers from the design of the WDM system.” Algety received a vote of confidence on the technology in March when a second round of venture capital funding raised $31 million.