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Service providers seek Holy Grail of all-optical network.

Promise of bargain-priced, on-demand bandwidth.

Optical technologies are creating new and more cost-effective ways to build and configure public network infrastructures.

For enterprises, these next-generation optical networks hold the promise of on-demand bandwidth of huge capacities at a fraction of today's cost. To realize this promise, service providers will have to build intelligent, all-optical networks, where traffic travels as light from end to end without requiring conversion from optical to electrical and back again for switching and amplification.

The intelligence, which is needed for rapid and flexible provisioning of new services and other management functions, remains a challenge. However, service providers have made considerable progress in creating high-capacity optical backbones using dense wave division multiplexing (DWDM) to boost the capacity of existing fiber-optic links.

Having established these high-capacity IP backbones, service providers are now extending the benefits of DWDM to metropolitan networks, and are moving gradually toward all-optical networks by incorporating optical amplifiers and switches into their infrastructures.


Today's DWDM systems allow service providers to increase each fiber's capacity by up to 160 times (See "DWDM heralds era of bandwidth abundance," Communications News, October 2000). They do so by simultaneously carrying multiple optical signals over a single fiber at different wavelengths.

Each wavelength represents a separate channel, or "lambda," of optical information, which can be either voice, data or video. In essence, DWDM creates a series of virtual fibers from a single fiber, each with its own logical domain as a partitionable data stream. DWDM hardware is expensive, but it's cheaper and faster than digging up city streets and laying new cable.

DWDM systems employ optical amplifiers to regenerate the optical signal, allowing it to traverse longer spans in the network backbone. An important development was the discovery of an element called erbium for use as a doping agent. Erbium proved to be a good amplifier at the infrared wavelengths where glass fibers are clearest. Also, erbium-doped amplifiers can amplify signals across a range of wavelengths, making them suitable for DWDM applications.

DWDM systems typically include a pair of terminals, one or more optical amplifiers, and, in some cases, an optical add/drop multiplexer (OADM). The OADM is similar in function to a SONET add/drop multiplexer, and allows the optical signal to be split, such that any number of separate channels can either be dropped from or added to a multiplexed signal. Some systems are standalone devices, and others are functionally integrated into other products such as optical amplifiers.

Another important element is the optical switch. Service providers with optical networks require full-scale optical cross connects in their large switching centers to direct signals from input to output ports, performing essentially the same functions as nonoptical cross connects or DACS systems. These functions include grooming and connecting large pipes in the carrier's backbone network.

One switching technique uses arrays of tiny mirrors that tilt back and forth on two axes to reflect light precisely from input to output ports. The mirrors are tilted to the required angle by applying voltages to circuits on the supporting semiconductor substrate. Another design uses mirrors with only two positions, either flat or sticking out, so that a light beam aimed parallel to the surface either passes by or is reflected to an output port. One optical startup, Xros, Sunnyvale, CA, now a subsidiary of Nortel Networks, claims that its design can handle up to 1,152 ports.

Other vendors, including Agilent Technologies of Palo Alto, CA, are developing rival microbubble switches using two intersecting sets of parallel waveguides embedded in a substrate of lower refractive index, which traps the light in the waveguides. Tiny liquid-filled holes at the intersecting points do the switching. As long as liquid is in the junction. the light passes straight through. Introduce a microbubble, though, and the change in refractive index causes the light to be reflected into the intersecting waveguide.


Several vendors are working on optical wavelength converters, tunable lasers and other components for the all-optical network, but the total solution, including the management systems, remains elusive. Given the potential payoff, though, there are plenty of startups looking to pioneer various niches, and possibly to position themselves for acquisition by the major players.

Nortel Networks paid $3.25 billion in common stock for Xros to acquire its micro-mirror technology and to counter the competitive threat from Agilent and Lucent Technologies' LamdaRouter, which can switch 256 light paths at the same time.

Nortel also paid $3.2 billion last December for Qtera, a Florida-based provider of long-reach DWDM solutions for service provider optical-backbone networks. The Qtera technology is based on advanced optical amplifiers, which use nonlinear modulation schemes and high-performance application-specific integrated circuits to extend the signal's reach.

Regeneration devices are a major expense in long-haul routes, accounting for as much as 30% of outside plant costs. The Qtera amplifiers can extend the range of a long-haul optical link to 4,000 km without requiring regeneration, though the technology becomes cost-effective at distances beyond 600 km. Besides saving on network operating and maintenance costs, the technology makes turning up new services easier and faster when the service provider does not have to deploy regenerators every 400 km.

Nortel has packaged the Qtera technology in its Optera Long Haul 4000 optical line system. Likewise, the company has adopted the technology from its acquisition of Cambrian in December 1998 into its Optera Metro transport portfolio for metropolitan networks. More recently, Nortel acquired CoreTek Inc., a pioneer in tunable lasers and other optical components, and Photonic Technologies, an Australian company specializing in optical component technology for manipulating and controlling polarized light.

Photonic's circulators and dynamic gain-flattening filters are critical technologies for DWDM networks. Tunable filters avoid having to keep separate laser inventories for each wavelength channel in a DWDM system. With Nortel's Optera Long Haul 1600, for instance--which scales to 1.6 Tbps per second by multiplexing 160 channels of 10-Gbps data over a single fiber--imagine the logistics of keeping spares for each channel at every node in the network.

DWDM pioneer Ciena Corp. of Linthicum, MD, has also used acquisitions to broaden its product portfolio in two important areas of optical networking: optical cross connects and fiber termination devices. Its March 1999 acquisitions of Lightera of Cupertino, CA, and Omnia of Marlborough, MA, for $980 million in stock provided the foundation for Ciena's LightWorks initiative, which establishes a blueprint for intelligent optical networks. The LightWorks architecture integrates optical transport, core switching and multiservice access technologies with software-based intelligence embedded throughout the optical layer.

Ciena's MultiWave CoreDirector, based on Lightera's flagship product, is described as an intelligent optical cross-connect system able to replace both legacy cross-connect systems and the SONET add/drop multiplexers used in conjunction with those systems. Omnia's multiservice transport platform is also aimed at the SONET-replacement market, as well as new growth in multiservice access.


Not to be outdone, Cisco Systems has also been active in the optical networking acquisition scene. Cisco's initial acquisition of startups Monterey Networks and Cerent in August 1999 originally raised more questions about the company's optical strategy than it answered.

Acquiring Monterey Networks, a developer of DWDM-based optical cross connects, for $500 million was hardly likely to cause concern for arch rivals Nortel Networks and Lucent Technologies, the analysts argued. Plus, at $6.9 billion, Cerent's tab was the largest amount Cisco had paid for an acquired company. Had it paid too much for a supplier of a SONET product when DWDM was the more advanced technology? Would Ciena, a company with which Cisco already had a strategic relationship, have been a better acquisition?

Cisco provided some answers four months later by paying $2.15 billion in stock for Milan, Italy-based Pirelli Optical Systems. Besides filling a gap in its optical strategy, the acquisition gave Cisco a wealth of technology, as well as revenue, customers and an immediate and credible DWDM market presence--especially in Europe. In addition, Cisco gained the capability to integrate DWDM with other platforms, such as its GSR 12000 high-end router.

After a long silence over its plans with the Monterey optical-switch technology, Cisco finally announced in August that Worldcom was testing the so-called Wavelength router, and that PetroNet, an Englewood, CO-based fiber-optic network builder, had agreed to buy one.

Meanwhile, Sycamore Networks, Chelmsford, MA, announced that 360networks, an international provider of broadband services, would be the first to deploy its intelligent optical switch. In addition, Ciena has said it has won a contract from Williams for its optical switch. Lucent Technologies, which has been promoting its competing WaveStar LamdaRoute, also announced that Global Crossing has begun live testing of the all-optical switch and will turn up service by the end of the year.

Global Crossing says that maintaining all-optical traffic through its 200-city, five-continent optical network will enable it to offer "point-and-click wavelength provisioning." This, in turn, will allow network providers to instantly redistribute wavelengths to areas of their networks that need additional bandwidth.

Lucent has always been a force in DWDM development, buoyed by Bell Labs' work on seed technology. Lucent was first to market with an eight-channel DWDM system in 1995, which was upgraded to 16 channels a year later.

The new products continue. In September, Lucent announced the first 40-Gbps optical receiver for next-generation optical networking systems and the industry's first 20-channel tunable laser module. In addition, Lucent has joined the acquisition drive by buying Chromatis Networks of Herndon, VA, for $4.5 billion in stock. Lucent was attracted, in part, by Chromatics' new technology, which can reportedly reduce the cost of building metro optical networks by one half, while radically improving their performance.

Lucent has also said that the head of its optical networking business will leave as part of a restructuring of the unit following manufacturing and product introduction problems that hurt profits in recent months. Under the restructuring, Lucent will split its optical business into two units: one will focus on products for long-haul networks and the other on products for regional and metropolitan networks.

Edwards manages communications and network consulting for IDC, a global IT market research and consulting firm headquartered in Framingham, MA.
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Title Annotation:Technology Information
Comment:Service providers hope to offer bargain-priced bandwidth on demand by deploying high-capacity optical backbones and dense wavelength division multiplexing (DWDM).
Author:Edwards, Morris
Publication:Communications News
Geographic Code:1USA
Date:Nov 1, 2000
Previous Article:NETWORLD+INTEROP 2000.
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