Sycamore box shoots for long reach, high capacity

By Tim Greene, Network World |  Networking

CHELMSFORD, MASS. -- Long-haul carrier networks that rely as much as possible on pure optical networks will get a boost from Sycamore Networks' latest piece of equipment, the SN 10000 optical switch.

The new box supports many optical interfaces and amplification options that let carriers support fiber spans ranging up to 4,000 kilometers without relying on expensive electrical signal regenerators.

The flexibility of the SN 10000 makes it possible for service providers to buy only the capacity required for the distance that needs to be covered, saving on initial capital outlay. The boxes are modular enough to add capacity later if that becomes necessary, says Christopher Nicoll, an analyst with Current Analysis in Sterling, Va.

The switch features high capacity and long reach, but supports one at the expense of the other. So at the high-capacity end, a carrier could support up to 160 wavelengths on a single fiber via dense wave division multiplexing - a staggering 1.6 terabit/sec capacity using lasers that transmit at OC-192 speeds. But that would be over a span of only 800 kilometers if only optical amplification were used.

Alternatively, at the long-distance end, the SN 10000 supports spans of up to 4,000 kilometers, employing purely optical amplification techniques. But to accomplish that, the capacity has to back off to just 40 wavelengths per fiber, or a total of 400G bit/sec.

Service providers can pick options that allow capacity and distance parameters that fall between the two extremes.

This is an advantage over less flexible equipment made by Nortel Networks and Ciena, according to Maribel Dolinov, an analyst with Forrester Research in Cambridge, Mass. The SN 10000 is also smaller than the largest network-backbone switches, she says. "This is an in-between size, and there are not a lot of in-between boxes. If you needed one this size from another vendor, you would have to strip down one of their core products," she says.

Sycamore uses a technique called RAMAN amplification, which strengthens optical signals by blasting bursts of proper wavelength light down the fiber in the opposite direction. Service providers can employ one, both or neither depending on the fiber span being connected and how much traffic it has to support.

Sycamore says Scandinavian carrier Utfors, which is constructing an end-to-end optical Ethernet network for delivering IP services, plans to use the ultra long-haul capabilities of the SN 10000 to complete a fiber link across the Baltic Sea between Sweden and Finland. Using RAMAN amplifiers, the company will be able to island-hop across the sea without needing expensive underwater equipment that requires constant maintenance, according to Peter Hunt, a product manager at Sycamore.

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