The changing transport landscape

Bandwidth pipes are integral to a service provider's business, and efficiently and cost-effectively delivering services over those pipes is taking center stage. With optical networks, pulling more out of every fiber and wavelength is a priority. Those priorities are being addressed with more advanced wavelength services.

Although many vendors seek to tap the available bandwidth in existing networks, many are trying other methods. Ciena is developing the transparent service multiplexing (TSM) platform, which enables carriers to sell transparent wavelength services without having to use an entire wavelength for lower traffic speeds or to add proprietary data rates for new services.

"We are looking at ways for carriers to deliver a set of customized optical tools for their customers," said Dave Polifko, director of technical marketing for Ciena. "We are allowing service providers to differentiate not only with their services but with their networks as well."

If a service provider uses standard Sonet, networks will not vary much. But with TSM, service providers can transparently multiplex multiple signals, transport them and demultiplex them as though it were one wavelength connecting the destination equipment (see figure).

"It is great for customers with a lot of low-speed signals or terminals that want to multiplex them up into a higher speed signal," Polifko said. "They don't want to `burn' wavelengths."

A typical wave division multiplexing system with four 622 Mb/s terminals usually would use four wavelengths. With TSM, the customer could put those terminals into a 2.5 Gb/s multiplexer and use only one wavelength.

Enron Communications plans to test TSM, which is slated for release in the third quarter.

"Conceptually, it allows us to take an OC-48 wavelength and split it into smaller increments, but it still looks like a wavelength to customers," said John Griebling, vice president of network engineering and operations for Enron Broadband Services. "It gives us the ability to deliver wavelength-style transparent connectivity at the OC-12 and OC-3 levels."

While OC-48s appeal to larger carriers and ISPs, OC-12s and OC-3s appeal to smaller providers and large enterprises, Griebling said. The efficiencies afforded by the technology make lower-capacity service offerings more feasible.

In addition to the denser pipe, Ciena touts the security and integrity of the TSM signal. But that's not a big draw for Enron, Griebling said.

"While it is true that a wavelength is inherently more secure than a circuit, the security level afforded by circuits is already high," he said. The benefit for Enron is the ability to emulate a wavelength at lower speeds, in a way that meets its security criteria, he said.

The technology seems to be more economical because it makes it easier to share wavelengths and get more out of the fiber that service providers have in the field, said Dana Cooperson, director of transport and optical networks for RHK. "It's reflective of attention shifting from pipes to more service-oriented capacity arrangements."

Ciena is not the only one shoving more data into wavelengths. Alidian Networks, Chromatis Networks, Kestrel Solutions, Siara Systems and Sycamore Networks also are developing similar technologies.

"The problem with the technologies out there is that they are really meant for long-haul, and when you try to move them to the metro, it is not cost-effective," said Ted Rado, director of marketing for Alidian. "The other problem is that the wavelengths still have to travel point to point."

Alidian's technology, which should be available in June, also divides wavelengths, but it can "add and drop at any node around the infrastructure without burning additional wavelengths," Rado said.