Posted: 04/1999
The Long and Short of WDM
By Barry Flanigan
Impressive progress, certainly. But now as the embryonic stage of WDM's evolution draws to a close, it is pertinent to assess the new directions technology will take, in particular the much-vaunted extension of WDM to the short-haul local exchange carrier (LEC) environment. Unfortunately, it is here that a great deal of confusion--not to mention hype--seems to exist in the industry.
The case for WDM in the long haul now is well understood. The increased capacity and cost benefits on long distance routes mean that it has become a "no-brainer" to deploy WDM in such applications. When long-haul carriers such as Sprint Corp. and AT&T Corp. first started purchasing WDM systems in large numbers to relieve exhausted fiber in 1996 and 1997, the next step seemed obvious--extension of WDM to the metropolitan and access regions of the network. Industry watchers predicted the market for so-called "metro WDM" to grow in the same explosive fashion in 1998 that occurred in the long distance environment in 1996 and 1997.
| The ability to provide a dramatic jump in capacity, while simultaneously reducing the cost per transmitted bit, rapidly has made wavelength-division multiplexing (WDM) an established part of the long distance transport network. |
However, as of today, that explosion has not occurred. Many LECs are in trials with the technology, and the first commercial applications in metropolitan environments have begun, but widespread commercial deployment has not proceeded as rapidly as predicted.
So what happened? One factor creating confusion is the "short-haul" WDM
environment being referred to as if it were a homogeneous market. This in the past led to
the mistaken view that once WDM became cost-effective for one LEC's network, it would
necessarily become cost-effective for all
metropolitan/interoffice networks, feeding predictions of a market explosion. However, the
local environment is not homogenous. Metropolitan, interoffice and access networks consist
of a diverse range of architectures, bit rates, traffic patterns and protocols, in
contrast to the long distance environment that is evolving from an established,
standardized synchronous optical network (SONET) base. The economics of WDM compared to
alternative solutions are, therefore, much more complex.
Cost is clearly a major issue. Although the cost of systems continues to fall, WDM has not broken significant price barriers in the short-haul market yet. Unlike the long distance environment, there has been no obvious "killer application"--an economically compelling reason to deploy WDM in the majority of cases, over all other solutions.
In the short term, therefore, the decision to deploy WDM in the local environment appears to be driven by simple network congestion and cost considerations--where WDM is cheaper and/or more readily available than the alternatives for increasing capacity, then it will be deployed. This is occurring in those networks that are "fiber poor"--i.e. where existing fiber capacity is running out and there is a lot of traffic on interoffice facilities. However in "fiber rich" networks--where there are spare conduits for laying new fiber and/or network congestion is not so acute--WDM may not be deployed widely in the near term. It is fair to say that there will be room for a variety of solutions and the choice of technology will be decided on a case-by-case basis.
However, despite the relative lack of success thus far for metro WDM, simply looking at the technology in terms of point-to-point capacity increase is misleading. It is the move toward optical networking, or "photonics," that will be the key to the success of WDM in the local environment.
Optical networking, deploying WDM ring architectures as opposed to simple point-to-point WDM, potentially will provide a common method for transport regardless of signal format in the metro environment, giving LECs the ability to deliver new services more quickly while reducing the costs associated with delivery.
There will be an increasing need for this approach, due to changes in the industry itself. The emergence of so many competitive LECs (CLECs) since the Telecommunications Act of 1996 is engendering a new business approach in the local environment, opening up many windows of opportunity for new, lean, aggressive organizations, as well as exerting pressure on the incumbents to improve their own networks. The ability to provide flexible allocation of large amounts of capacity to multiple points in the network, making more intelligent use of scarce bandwidth resources, will be a key success factor. In this environment, flexible access rings deploying WDM will start to become a source of competitive advantage.
With the introduction of optical networking techniques comes the potential for wavelength services, opening up many possibilities for LECs. Service providers will be able to assign the end customer a set of wavelengths and route those wavelengths through the network independent of whatever service is being carried. The marketing of transport on a wavelength basis will enable operators to offer end users a way to enter the high-speed backbone in native formats, avoiding the costs of aggregating multiple service types--for example, deploying datacomm solutions such as gigabit Ethernet directly on an optical wavelength.
How close is the WDM industry to this vision? There continue to be improvements in the price and functionality of WDM systems from vendors, but there still are challenges to overcome. In particular, concerns surrounding network management, performance monitoring and vendor interoperability must be addressed before LECs will have full confidence in optical networking solutions, particularly as they deploy large numbers of wavelength channels in the network.
What is clear, however, is that the foundations for the future all-optical network must be laid today. The way in which WDM develops in the network in 1999 will be critical to the way in which bandwidth is supplied, priced and managed in the next decade.
Barry Flanigan is senior analyst at London-based Ovum Ltd. and lead author of Ovum's recent report, "WDM: Global Strategies for Next Generation Networks." For more information visit www.ovum.com.
