mci strategizes fiber, wdm, and OC-192 abilities

mci strategizes fiber, wdm, and OC-192 abilities

stephen hardy

MCI Corp., the U.S. long-distance giant, flexed its fiber muscles, introduced new services, and made several bold predictions and guarantees before an audience of analysts, journalists, and customers at its first Network Technology Day in Boston. While the service introductions occupied center stage for most of the event, speakers reiterated the company`s commitment to fiber-based transmission technologies as an important component of its overall network mix.

Fred Briggs, mci`s chief engineering officer, started the proceedings by emphasizing mci`s prowess in fiber using both OC-192 (10-Gbit/sec) and wavelength-division multiplexing (wdm) technologies. He predicted that mci will evolve its OC-192 networks to attain even-higher speeds and claimed that the company`s networks would use "OC-1536" (80-Gbit/sec) rates in the foreseeable future.

Jack Walters, vice president, network systems engineering, then reviewed mci`s history of fiber development, culminating in recent field trials in which the company achieved 40-Gbit/sec transmission rates using OC-192 plant (see Lightwave, March 1997, page 1). Walters said OC-192 will remain important to the company because it provides high capacity at an economical cost--a price 35% to 40% lower than equivalent OC-48 2.5-Gbit/sec capacity. He explained that multiwavelength use over singlemode fiber means OC-192 also provides improved fiber utilization.

Meanwhile, he said, mci will complement its OC-192 lines with 4-wavelength wdm. Walters contrasted mci`s approach to wdm with that of "conventional" approaches (see figure on page 1). The conventional approach calls for two lasers: an initial transmitter with a wide, typically 2.5-Gbit/sec output, and a second laser, which generates an "improved" 2.5-Gbit/sec-dependent output after the initial transmission has been received and reconditioned. The mci approach, Walters said, requires only a single laser--with strict tolerances--that provides a 10-Gbit/sec output. The result, he said, is that the mci approach can provide up to 400 Gbits/sec, compared to the 100-Gbit/sec potential mci estimates for conventional wdm systems. His company`s approach is also 30% cheaper than conventional methods, Walters claimed. oca, jds Fitel and E-Tek Dynamics Inc. provide much of mci`s wdm equipment.

Walters estimated that 30% to 40% of mci`s current fiber plant uses wdm. He revealed that company engineers have started to work toward 16-wavelength wdm and said 48-wavelength compression might eventually be attained.

In a separate discussion, Joseph Cook, director of network equipment engineering, revealed some of mci`s strategy for deploying wdm. The company`s deployment plan for Synchronous Optical Network technology, which includes the use of lasers emitting at a specific wavelength and with the tighter tolerances highlighted during Walters`s presentation, enables the use of narrowband wdm devices, as well as other benefits. "On nondispersion fiber, we are basically following the itu [International Telecommunication Union] plan and buying standard industry components," he explained. "In designing a system, there are three components you try to maximize: speed, distance, and number of channels. Unfortunately, sometimes you have to trade off one for the other." Regardless of the trade-offs, Cook reported that the company has achieved 10-Gbit/sec transmission speeds over nondispersion-shifted fiber, using "dispersion-compensating fiber to compensate for the high dispersion."

Cook said that mci has limited its use of dispersion-shifted fiber to small portions of the network, although such fiber enables longer spacing between sites. In these instances, the company used the same itu plan but selected the adjacent channel settings carefully, to minimize the effects of four-wave mixing.

Optical networking

In addition to the benefits provided by OC-192 and wdm, Walters said mci expects to realize a further savings of $20 million annually through the use of bidirectional optical transmission. Such a scheme will see bidirectional line amplifiers used to increase the spacing between wdm regeneration sites, with transmit traffic running at 1545 to 1560 nm and receive traffic occupying 1530- to 1545-nm channels. wdm equipment at each end of the link will combine OC-192 transmit-and-receive systems.

Meanwhile, mci also plans to field OC-3 switch peripheral modules in the next nine months. The goal, said Walters, is an all-optical central office, which would include optical OC-3 155-Mbit/sec switches that would provide a 400% capacity increase over present T1 switches in a package 75% smaller.

Walters ended his presentation by predicting the appearance of OC-768 (40-Gbit/sec) transmission rates and dense wdm by the end of the decade, along with optical signal processing and optical crossconnect-based restoration. Walters said he foresees terabit networks using optical frequency-division multiplexing, switching, wavelength routing, logic/memory, and computing in the early years of the next century.

In a separate discussion, Walters said mci`s current plans for new fiber will focus on the company`s efforts to break into the local exchange carrier market. Walters said mci hopes to reach an additional 30 cities by the end of this year and a total of approximately 50 additional cities in the next 12 months. How much fiber will be required will depend on the needs of each application; Walters said mci might meet some fiber requirements by leasing existing capacity.

Service expansion

mci will use its entire repertoire of transmission technologies as a platform to introduce several new services, which subsequent speakers detailed. One service announcement that plays off mci`s fiber investment is the development of a software-based technology in conjunction with Cisco Systems Inc., which will enable it to provide premium-grade Internet service to customers willing to pay for it. The "Quality of Service" offering will provide its customers with priority access to network bandwidth and ensure a stated level of network performance.

The announcement has several ramifications, according to Traver Kennedy, director of wide-area-network services and research at the Aberdeen Group in Boston and an analyst who attended the Network Technology Day presentation. "It demonstrates that quality of service--meaning latency, availability, and bandwidth--is now a business consideration in terms of differentiated value in intranet/Internet offerings," he explained. "I think there`s a lot of pressure for quality of service. Now the ante goes up, both for voice carriers and for Internet service providers or the new-entrant data network folks."

mci`s work with fiber for Internet backbones--which has seen it move from OC-3 to OC-48--puts the company in a position to make such quality-of-service offerings, Kennedy said. "Obviously, the benchmark has been moved up for other carriers, and other carriers have to really consider how they are architecting their networks and how they are provisioning them locally to meet needs."

As mci and its competitors look to improve quality-of-service attributes by investing in their networks--particularly to lengthen the distance between routers--the fiber-optic community should benefit. "What it means is that you need more fiber in the core, and you need faster boxes at each end of that fiber," predicted Kennedy, who added that carriers will place a premium on wdm and "other types of technologies that are absolutely required to be invoked."

mci also made other Internet-related service announcements, including the introduction of its first V-Class Internet products based on its new vault network architecture code. vault converts communications traffic into Internet protocol packets and sends them over the company`s Internet backbone, using a single line. mci has already used vault to provide enhanced features to its directlinemci customers, and plans to use it to provide personal features to its call-center services. The company also unveiled a video-distribution service aimed at advertising agencies, in which mci would function as a server as well as a communications service provider.

In moving aggressively into the Internet, mci is not forgetting more mainstream services. For example, the company will provide international Asynchronous Transfer Mode (atm) service to the United Kingdom. The HyperStream service will link with British Telecom`s CellStream atm service; mci will market the service to large corporations and government agencies. The service introduction represents another step toward combining the two companies into an entity called Concert, a plan announced late last year (see Lightwave, December 1996, page 1). q

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