TELECOMMUNICATIONS

Telecommunications has been a cornerstone in the Information Revolution.

The promise of dense wavelength-division multiplexing (DWDM) has been its ability to multiply fiber capacities by factors of eight, 16 or even 32, essentially giving bandwidth for free.

But in so-called "metro" DWDM applications, the technology has been anything but free, as vendors' current solutions for DWDM in short-haul applications have been so expensive that it often is cheaper to lay new fiber than to install DWDM. To make matters worse, DWDM is less flexible and does not have the monitoring, management and restoration features of the technology it would replace--synchronous optical network (SONET).

New DWDM solutions demonstrated at the recent OFC 99 fiber optics conference in San Diego showed that vendors have made strides in addressing some of the concerns of competitive local exchange carrier (CLEC) users, particularly flexibility. With these advances, DWDM can be an appealing solution for service providers that have the capital and customers to move toward high-bandwidth services.

Weighing DWDM vs. SONET
	Metro DWDM	SONET
Cost	Still expensive	Prices dropping fast
Bandwidth	8X to 40X current capacity	Limited ability to scale
Overhead	Low	High
Monitoring	Not well-developed	Built into technology
Restoration	Can be lengthy	50 milliseconds
New services	Can sell wavelengths, gigabit Ethernet, other high-bandwidth services	Limited to SONET multiplexes such as OC-12, OC-48

For much of the rest of the industry, however, the choice of DWDM vs. SONET is a difficult one. It is a decision many carriers are opting not to make, as they wait for cheaper technology and more demand from customers. CLECs typically consider doing a metro DWDM upgrade today primarily where there is a situation of fiber exhaust. At that point, the question becomes whether to pull new fiber or install DWDM to get the added capacity of more wavelengths of light.

It depends on how a CLEC's fiber is deployed, but very often it is cheaper simply to install new fiber to alleviate a fiber exhaust situation than to deploy DWDM. If a company has unused space in conduits, that is the most ideal situation to deploy new fiber, and, in that case, a DWDM deployment would be unlikely. However, if a new fiber build would involve trenching, the higher cost could justify the move to DWDM.

These decisions are very distance-sensitive, network operators say. For the long-haul industry, the decision was easy because adding hundreds of miles of fiber was cost-prohibitive and their point-to-point networks needed DWDM nodes only at each end. However, CLECs tend to operate short networks with multiple nodes, and must have add/drop multiplexers (ADMs) at each node, which adds more cost.

Phil Markwart, senior engineer of long-haul transport at GST Telecommunications Inc., Vancouver, Wash., says that for GST, DWDM is cost-effective in its longer metropolitan rings, such as Los Angeles, if it can add at least three new OC-48 customers on the network. In a smaller ring, as many as six or eight new OC-48s would be needed to break even or make a profit.

Many industry observers believe, however, that metro DWDM should be considered primarily as part of a larger strategy to change the kind of services offered by a CLEC.

"We say that it is not fiber exhaust that will bring in metro [DWDM] but rather wavelength services," says Dana Cooperson, senior analyst at Ryan Hankin Kent Inc., San Francisco. "New products and new ways to use them in existing applications are what will make metro happen."

Also, she says, "We don't see exhaust as a major issue in metro [applications], except in a few instances, because [CLECs and incumbent LECs (ILECs)] have a lot of fiber in the ground, or it is easy to lease."

According to Greg Wortman, senior director of marketing at Fujitsu Network Transmission Systems Inc., Richardson, Texas, a couple of carriers are making more strategic decisions in the area of DWDM.

"Level 3 [Communications Inc.] is taking a very strategic perspective, as is e.spire [Communications Inc., Annapolis Junction, Md.] and others, about DWDM ... as something to use to win business and increase business," Wortman says.