Ever-increasing wavelengths - Telecom 99 - Industry Trend or Event

Since 1995, WDM has steered the industry into the fast lane. It's now preparing to push the bandwidth throttle to the floor.

One of the most spectacular technology growth stories since Telecom 95 has been the development of "wave division multiplexing," WDM, which allows the transmission of multiple signals through a single optical fiber.

This simple concept, where each signal is transmitted on a separate wavelength (or color, in optical terms), lies behind the massive growth in transmission capacities of core telecoms networks over the last four years--which in turn has been essential for supporting the growth of Internet use.

WDM system vendors have rapidly increased the number of wavelengths--each carrying usually either 2.5 or 10-gigabit-per-second signals--that can be transmitted since the first four-wavelength and eight-wavelength systems were released onto the market in 1995 and 1996.

According to Mike Parmline of Lucent Technologies Inc., Murray Hill, New Jersey, it was not that long ago that none of the operators saw the need for more than 16 wavelengths in a system. Indeed, Sprint now it will not look at anything with fewer than 100 wavelengths as its WDM platform, added Parmline.

The initial driving force behind the development of WDM was this urgent operators' need for extra capacity, as fiber in core networks became saturated. But at Telecom 99 it will be assumed that an ever-increasing number of wavelengths can be supported--and that higher time-division-multiplexer rates such as 40 Gbps and 100 Gbps will soon be commercially available as well. Developments in laser and optical amplifier technology should ensure a continued exponential increase in the capacity of fiber optics for the foreseeable future.

Silicon economics

"A few decades ago a transistor cost several dollars," says David Lee, president of Global Crossing Ltd., Hamilton, Bermuda. "Today each transistor on an integrated circuit costs one-millionth of a cent. This 'silicon economics' hasn't so far been applied to telecoms, but now with the advent of fiber-optic economics we will look back and say that there was a major change in telecoms at this time."

Attention at Geneva will be focused on two consequences of this: new operator strategies made possible by WDM systems; and new developments that have the potential to change WDM from a point-to-point capacity upgrade fix into just one strand of optical networking technology. All-optical networking will remain a distant and probably unachievable aim, but Telecom 99 will certainly see the release of products that will transfer many of the functions currently performed in electronics into the optical layer. Dozens of vendors will present optical networking products and systems at Geneva.

Ciena launch

Optical networking specialist Ciena Corp., of Linthicum, Maryland, for example, is launching its Optical Switching and Routing Protocol (OSRP) at Telecom 99 to tackle the real issue in optical internetworking: managing it all. The company plans to deal with such issues by handling capacity provisioning and routing within optical networks linked by dedicated electronic switches. "Routing determines the path optical channels will take through the network, while signalling makes it happen," says Rick Dodd, product management director at Ciena. He says OSRP is intended to provide operators with the means of providing efficient and cost-effective optical networking. "Operators have to be able to provide service quickly and to control quality in the optical network."

The most visible result of WDM is the rush of operators setting up pan-European networks. Some of these companies, such as Global Crossing, New York-based Viatel Inc. and i-21 (formerly Interoute) are digging in their own ducts and pulling through cables containing scores of fibers. Others, such as Iaxis BV, Hermes Europe Railtel BV and Fibernet Group plc, are building networks by leasing a single fiber from utilities such as road, railway and electricity distribution networks, which have already laid cables with bundles of fiber. They then plug their own WDM systems into this "dark fiber."

London-based Iaxis, for example, is focusing on providing capacity to other carriers over its leased dark-fiber network. It is the massive capacity of its WDM systems, from Ciena, that allows it to tackle the carriers' carrier market with just one fiber.

The Ciena system carries up to 40 wavelengths with 10-Gbps signals or 96 wavelengths with 2.5-Gbps signals; it is also possible to run wavelengths carrying both TDM rates in a single fiber.

Initially Iaxis has "lit up" just six wavelengths, but it can add extra wavelengths as demand increases by plugging in extra WDM wavelength cards. Ciena's Smartspan management system recognizes the new wavelengths and automatically adjusts components such as amplifiers without manual intervention.

However, at the other end of the scale is Global Crossing, which will turn on the first phase of its pan-European network shortly after Telecom 99.

The company is digging in ducts that are capable of carrying several cables each with up to 144 fibers. Despite this massive number of fibers, it still sees the need for WDM and has deployed a Lucent system, which also uses expensive new fiber that will support many more wavelengths in the future.

Global Crossing argues that it can only carve out a share of the global market for telecoms traffic by building enough high-quality capacity to keep on reducing prices faster than the competition for some time to come--which means it has to exploit the full potential of WDM.

Gary Winnick, chairman of Global Crossing, says the company's initial strategy was to provide extra submarine capacity, but it rapidly recognized the need for "city-to-city" connectivity.

"Now we're going to go from building to building." he says.

The company's rapid transition from new submarine cable operator to full services provider was based on its acquisition of Frontier Corp. and the capacity of a WDM-enabled network to carry any amount of traffic.

The key difference between laxis and Global Crossing is their contrasting expectations of the rate at which the demand for traffic will grow; the key similarity is a business case enabled by WDM technology.

According to Global Crossing's president David Lee, "people worry about where the demand will come from, but in telecoms the supply side plays an important role. This is because of the breakthroughs in WDM and optical networking."

What's on show

Attention at Telecom 99 will focus on new products and systems that make the goal of "optical networking" a reality, with transmission networks organized by cross-connecting actual light channels, instead of decoding, switching and recoding the data contained within them.

Most WDM system vendors already offer "optical add/drop multiplexers" (OADMs), which allow WDM systems to be constructed in rings. This opens up possibilities for more complex forms of networking. For example, carriers may then be able to make WDM rings self-healing and interconnect them to form meshed networks, introducing an ability to provide protocol-independent--rather than Sonet/SDH-based--optical channel links between end points for customers.

According to Keith Gibson, director of sales and marketing at Birmingham, England-based Fujitsu Telecommunications Europe Ltd., connectivity became an issue once a series of viable WDM solutions became available to solve capacity-based limitations.

One possibility is carrying Internet Protocol traffic directly over WDM without recourse to the intervening ATM and Sonet/SDH layers. In the United States, operators such as Enron Corp., Houston, Texas, and Williams Communications Inc., Tulsa, Oklahoma, are building networks on this basis.

And Reading, England-based Racal Telecom recently announced that it will run IP directly over the WDM system to provide voice and data services to corporate customers, with Cisco routers handling recovery routines when packets are dropped. Racal will run the IP/WDM traffic on the same fiber as its other SDH-based data and voice traffic; it hopes to exploit the cost advantages of IP to the maximum by reducing the number of protocols. This is possible due to the ability of the WDM system to carry multiple protocols.

"Siemens has transmitted gigabit Ethernet over 1,570 kilometers and proved that it is not restricted to the campus area, but can also be used for long-distance communication networks. Any data format can be transported over long distances without the current practice of converting it to SDH format," says Stephan Neidlinger, vice-president in the product management of optical transport networks at Siemens AG, Munich.

Once carriers start to offer transparent optical bandwidth services, this market is likely to become very important. But not everyone agrees that this will be the dominant trend. ECI Telecom of Israel is concentrating on extending the reach of SDH all the way to customer premises over fiber in the access networks, but tied into metropolitan and core WDM networks with its BroadGate product, being launched at Telecom 99. "SDH will remain the basic transport layer," says Eran Dariel, ECI's vice-president of marketing. "We don't believe in religious wars. IP will grow faster, but protection mechanisms will not develop so quickly in the optical layer, as it requires software." Even with IP over WDM, he adds, "The framing structure is still SDH/Sonet."

"The investment that's been made in SDH and Sonet is so substantial: that we've got an enormous legacy, so demand for Sonet gear will remain strong," says George Peabody, managing director of telecoms research at Boston, Massachusetts-based consultancy the Aberdeen Group. "But the disruptive technologies of, optical networking coming up from below will eventually get us to the point where carriers think in non-Sonet terms."

COPYRIGHT 1999 EMAP Media Ltd.
COPYRIGHT 2000 Gale Group