Just some research info...isn't the optical crossconnects,(OCC), similar to the confusing, 'Dynamic'DWDM announced recently by MRVC?
"...In contrast to current generation DWDM solutions, MRV's Dynamic DWDM will create an optical layer for the access network. This optical layer will perform routing, switching and optical cross connect
functions completely in the optical domain."
The data is the driver. (telecommunications carriers' use of dense wavelength division multiplexing technology)
Carriers speed along the DWDM highway.
Data is about to take the place of voice in the driver's seat as far as the evolution of the public switched telephone network (PSTN) is concerned. Trouble is, the two are trading places without stopping the car. Progress has been slow in the land of technology, and it will be awhile before data and voice will be able to travel on different roads. The legacy of 100 years of voice-dominated networks, Sonet and time division multiplexing (TDM) technology will impact the delivery of data services for a long time to come. But never fear: equipment manufacturers and carriers plan to do some pretty creative stunt-driving as the data explodes all around them.
The Secret Weapon
Enter dense wavelength division multiplexing (DWDM), the alchemy that can turn what was one fiber optic network into 16 to 40 fiber optic networks today (and upward in the very near future) by packing
multiple wavelengths onto a single fiber line. In addition, each wavelength can transmit its payload at speeds of 2.4 Gbps or 10 Gbps per channel, or even a combination of the two, on the same fiber.
The future of the PSTN is in its ability to expand to accommodate the exponential increase in data traffic spurred by the Internet, telecommuting, videoconferencing, multimedia and voice-over-Internet
Protocol (VOIP), digital subscriber line, Gigabit Ethernet, and more. The ability to increase capacity so dramatically has arrived in the nick of time in the form of DWDM, which allows carriers to simplify
their networks for data services, according to Joe Berthold, vice president of network architecture for CIENA Corp.
Specifically Speaking
In short, DWDM is a proven technology. DWDM has already been widely deployed by the interexchange carriers (IXCs) in the form of 4-, 8- and 16-channel 2.4 Gbps systems. However, it won't be long before 2.4 Gbps systems begin to move into the long distance networks in a big way. Sprint recently became the first IXC to deploy a 40-channel system. The long distance provider chose CIENA's MultiWave Sentry[TM] 4000 to do the job, according to Marty Kaplan, senior vice president and chief technology officer at Sprint. The IXC is using DWDM to boost the capacity of its Sonet networks, many of which were deployed years ago, primarily on fiber cable with low fiber counts of 12 to 24 fibers per sheath.
Most carriers are using their DWDM networks to carry TDM-based traffic at Sonet speeds across their Sonet backbone networks and fiber optic rings. However, the emergence of ATM and IP switches and routers equipped with high-bandwidth interfaces in the multimegabit and gigabit range is likely to put voice services permanently in the back seat in the not-too-distant future, according to carriers, equipment manufacturers and analysts.
While it's true that IXCs have ATM switches in their backbones today, most of them operate at OC-12
speeds. Local exchange carriers (LECs) for the most part have deployed smaller ATM edge switches
in their networks and are only now considering backbone-sized switches.
Both IXCs and LECs plan to deploy the new high-bandwidth switches and routers to meet the surging data needs of their end-user customers. They're all interested in DWDM equipment that provides
direct interfaces to the new high bandwidth gear. "We want that capability," says John Spencer, manager of transport systems engineering for BellSouth. " That's more significant to me than being
able to roll over asynchronous traffic to DWDM systems. Putting data directly onto DWDM networks represents the future."
Carriers are concerned about eliminating the Sonet layer because of its potential impact on network reliability. While they are interested in placing data services directly onto DWDM systems, they want the new equipment to provide the reliability and protection features of Sonet transmission equipment and Sonet rings. However, they acknowledge that some of their more bandwidth-hungry customers are more concerned about getting capacity than they are about protection.
Vendors hearing the message are developing ring-architected DWDM systems that employ Sonet-like protection and can accept traffic from these high-bandwidth data switches and routers. "ATM switch vendors and IP router vendors that are looking at high trunk speeds are looking at providing protection integrated into their boxes as well," says Tom Mock, product marketing director-access products for CIENA. Once these systems and DWDM ring networks are deployed, carriers can simplify their networks by putting data traffic directly onto fiber equipped with DWDM. Bypassing the Sonet layer completely will save them money, and lots of it. That's because OC-48 and OC- 192 Sonet gear is much more expensive than DWDM equipment.
"As trunk speeds get higher on data switches, it will not be necessary to have Sonet in-between," Mock says. "Sonet is something that most operators are familiar with today, and it's a comfortable technology for them. What we are asking them to do is to change the way that they look at the network." Because carriers' network management infrastructures are based on the Sonet-TDM world, they will
have to make some adjustments to these systems to accommodate a new style of networking. "Not that it's brain surgery to do that, but every organization has its inertia," Mock says.
Although data will dominate network architectures of the future, experts agree that Sonet will not disappear. Indeed, they say, it will still be used to carry voice and low-bandwidth data services.
Metromania
While DWDM is practically old-hat to the IXCs, it's only now making the entry into the local network. As predicted by TransFormation Inc. analyst Mark Lutkowitz, Bell Atlantic made a first-quarter announcement of its plans to deploy about $30 million worth of DWDM equipment in its backbone network. The regional Bell operating company (RBOC) will begin installing CIENA's MultiWave[TM]
1600 16-channel, 2.4 Gbps system and MultiWave Firefly[TM] 24-channel system, as well as Lucent's WaveStar 16-channel, 2.4 Gbps/10 Gbps DWDM system, to alleviate congestion on its interoffice fiber links.
In the meantime, BellSouth is continuing to trial a point-to-point, 16-channel system and optical add/drop multiplexer in its lab. The RBOC plans to issue a request for proposal (RFP) in 1998,
according to John Spencer, manager of transport systems engineering at BellSouth. "If what we see in the RFP looks favorable, there's a possibility we could begin deployment by year's end," Spencer says.
"The applications are certainly out there if DWDM proves to be economical." Right now, DWDM proves in for BellSouth on interoffice links of 15 miles or more, he notes. "Economics are going to drive this," he adds. "If it's economical to meet capacity demand with
DWDM, then that's what we'll do. Operational concerns - the ability to inventory and alarm DWDM systems in existing operations support systems [OSSs] - are also at the top of the list of system requirements."
SBC Communications Co., an ILEC leader in Sonet deployment, plans to trial DWDM in the next 18 months, according to Renee Lau, Sonet product director for SBC's Sonet sales unit.
Sonet Delay Drives DWDM
Why does BellSouth find DWDM attractive? Because OC-192 Sonet systems with bidirectional line switched rings (BLSRs) are not yet widely available, according to Spencer. "We thought they would be
here last year, but it seems like we are hearing mid-1999 now. Fortunately, we have other tools in our toolbox we can use," he says.
The late arrival of OC-192 systems has been a "huge" factor in DWDM' s success, agrees Stephen Montgomery, president of ElectroniCast Corp. "The IXCs were not putting in fiber in anticipation of OC-192 in 1995, " he says. "They got stuck when they did not have enough fiber to meet a huge demand for bandwidth. The only alternative left for them was to go with DWDM."
Strong demand for metropolitan-area DWDM will begin to snowball over the next two years. In the meantime, the IXC market will be where the money is for DWDM vendors, according to Montgomery. LECs have other alternatives, primarily because of their relative ease of deploying new fiber, their access to rights of way and shorter interoffice link length. Luckily for them, the LECs have newer cable in their networks that contains hundreds of fibers per sheath rather than the relatively low fiber cable installed early on by Sprint and other IXCs. Today, fiber cable is available in counts of 300-plus per sheath, Montgomery observes. Carriers with these fat optical fiber cables in their networks have less of a need for DWDM.
It's also important to note that it costs LECs as little as $25,000 per mile to lay down new fiber, while it costs the IXCs nearly $75, 000 per mile, according to Ken Cook, manager of infrastructure planning for BellSouth.
An unexpected twist to the DWDM story is that the technology may actually spur fiber deployment by the competitive LECs (CLECs), according to Mike Viren, senior vice president of strategic planning
and regulatory for Intermedia. "Right now, it's more economical to lease fiber than it is to build Sonet networks," he says. "If DWDM lowers the cost of fiber, it could create an opportunity to invest in fiber in our current network. DWDM probably will not turn the LEC world on this year, but at the end of 1999 and the beginning of 2000 it will catch on fire. But we probably won't see any cost breaks until
1999."
At the Millennium
Within two years' time, DWDM will be making its mark in metropolitan area networks and around the globe. "Networks are going to become extremely data-centric, because trade and commerce between
North America and the rest of the world are going to explode and backbone networks are going to require huge amounts of capacity," says Pawan Jaggi of Fujitsu.
The DWDM market, which will total $1 billion for vendors in 1998, will at least double by 2000 or 2001, according to Brian McFadden, vice president of high-capacity systems and transparent networks
for Nortel. "I don't think we've scratched the surface on capacity, " he says. "Today, most people access the Internet via conventional modems and they are not using the Internet for large software
downloads. When access speeds reach 1 Mbps or higher, as they will with ADSL, we will start to see the demand for tremendous amounts of bandwidth on network backbones. Going forward, this will manifest itself in DWDM deployment to get more channels and more speed on those networks."
Observers predict the onset of optical layer networking by 2000. Commercial use of optical add/drop multiplexers able to dynamically add and drop traffic will make their way into long-haul networks in the next three years, as will optical cross-connects that can route individual wavelengths, Jaggi predicts. "Two years out, I see carriers beginning to build real optical layer networks," says Tim Krause, senior director of business development for Alcatel's optical networks business unit. "The first carriers to deploy real optical layer networks that will deliver wavelength services to end users will be the CLECs that aren't encumbered by legacy OSSs." CLECs are also prime candidates for DWDM and optical networking because of their focus on high margin, high bandwidth services. The technology will be the most cost-efficient and attractive way of making the most of their fiber networks. Besides, CLECs are looking for a way to do things better than the ILECs, and are willing to take more risks, according to CIENA's Mock.
Another important change in DWDM during the next two years will be the deployment of multiple channels. Systems offered by vendors today make it easy for carriers to meet the need for bandwidth
incrementally, because they can add one channel at a time. Therefore, they do not need to make capital expenditures that are not accompanied by a concurrent return on their investment. "Once a carrier has all of its optical amplifiers in place, the cost to add capacity is the cost of installing a plug-in card at both ends of the chain," says CIENA's Berthold. In addition, DWDM network management systems will also spur channel- by-channel growth, because they make it possible to deploy new channels without having to make manual adjustments to the
network.
According to Sprint's Kaplan, in 1998, 90 percent of Sprint's network will be supported by WDM/DWDM systems of eight, 16, 32 or 40 channels. Two years from now, the eight-channel systems will likely be gone, and the 16-channel systems will be reused for certain routes, he notes. Routes that use 16-channel systems today will be upgraded to 32- and 40-channel systems, and the carrier will deploy systems with more than 40 channels. "I think vendors will find ways to get outside the passband and put many, many channels on single, very short wavelengths," Kaplan says. "Right at the moment, I would not be surprised to find that by 2000 or 2001 we will have the ability to put 2.6 terabytes on a single pair of filters."
Catching the Wave
Over the next five years, wavelength routing and switching, as well as multiple wavelength interfaces will debut, according to Solomon Wong, director of product management for Cambrian Systems Corp. Wavelength service likely will turn out to be more of an operational challenge than technical challenge in the long run; however, five years from now, it will be a true tariffed service offering, Krause predicts. "It will be as easy to buy a wavelength in five years as it is to buy an OC-3 circuit today," Krause notes. "Also, carriers will be doing 40 Gbps over DWDM and they will have implemented optical layer restoration. They'll be able to take a wavelength into an optical cross-connect [OCC] and change its
color using software controls, and switch it to another port and send it out." Optical gateways and cross-connects will be the enabler for routine deployment of wavelength- based services," he adds.
Yet pure optical switching is still four to six years away, Kaplan predicts. Also, adds Nortel's McFadden, there are still plenty of issues to be addressed, including scalability in the optical domain to
maintain signal quality on all optical networks. Vendors will have to implement a means of determining if a signal is good as it passes through the OCC and they will have to devise ways to troubleshoot and
manage traffic in the optical domain to maintain the quality to which customers are accustomed. "The issues are all dependent on some technological and cost breakthroughs that are a-ways away," McFadden says. "There are still very few standards in the optical domain, and customers are going to want [fast] networks."
The trend toward multivendor networks already has been set by Bell Atlantic's selection of two vendors for its initial DWDM deployment, and Sprint's decision to select two vendors for the 40-channel systems.
Another development that will occur in the next five years is DWDM deployment in carrier access networks, according to Montgomery.
Although DWDM has been around for some time, the technology still is in its infancy, only now making extraordinary technological gains and winning solid acceptance in the metro area. DWDM's role in the network today and its role five years from now are worlds apart. "We are very early in this game," McFadden says. "I think the optical world is where the semiconductor industry was 20 years ago. In terms of manufacturing, cost, etc., we have a long ways to go. However those 20 years will pass in 10. And if we are real smart, maybe it will take five years. The good news is that there is a lot of money and being spent, and when that happens, we tend to do things faster."
05-15-1998
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