For tunability, is less more?

technology

By KATHLEEN RICHARDS

Despite their promises of cost efficiencies, inventory reduction, line-card sparing, and remote provisioning, manufacturers of tunable lasers are grappling with delayed fielding of their products caused by the slowing economy. Nevertheless, this year is critical for vendors of tunable components, as system manufacturers evaluate and design these technologies into their next-generation systems.

Tunability was the key feature on a host of products that debuted at the annual Optical Fiber Communications (OFC) Conference in March. Santur (Fremont, CA) launched its 10-mW, TL1010-C widely tunable laser, which uses a patented distributed-feedback (DFB) array to tune across 80 channels (at 50-GHz spacing) over the C-band. Santur is also sampling L-band and 20-mW modules.

Bandwidth9 (Fremont, CA) demonstrated a tunable-laser subsystem, the MetroFlex G2 transmitter, which integrates its directly modulated, tunable vertical-cavity service-emitting laser (VCSEL). The device uses a micro-electromechanical technology for tuning, wavelength locking, and amplification in a 2x3-inch package. The device supports wide tuning in the C- or L-bands, in a range of tuning options, from eight to 20 channels at 100-GHz spacing and from 16 to 40 channels at 50-GHz channel spacing.

Agility Communications (Santa Barbara, CA) unveiled a 10-mW widely tunable-laser assembly that monolithically integrates a tunable laser with a semiconductor optical amplifier (SOA). The SOA can also operate as a variable optical attenuator. The Agility 3105 CW Widely Tunable Laser Assembly uses an industry-standard 24-pin footprint.

Iolon (San Jose, CA) announced that its Apollo, a 20-mW widely tunable external-cavity laser, can now support 25-GHz channel spacing. That allows the laser to access more than 200 channels in the C-band and over 200 channels in the L-band, according to the company.

Fiberspace (Woodland Hills, CA) introduced Gridlocker, a 16-channel (3-nm), tunable laser designed for long-haul DWDM systems. It supports 25-GHz and 12.5-GHz channel spacing and features patented optical phase-locked-loop technology for accuracy and stability.

Down the familiar path
While system manufacturers appear receptive to products tunable over 10 nm or less (two to 10 channels with 50-GHz spacing), a cautious approach to the newer widely tunable technologies may slow traction in this market, according to at least one analyst. "It is getting bleaker all the time," says Tom Hausken, director of optical communications components at Strategies Unlimited (Mountain View, CA). (Strategies Unlimited is part of the PennWell Advanced Technology Div., which publishes Lightwave.) The market for tunable lasers, tunable filters, and wavelength converters is expected to reach $577 million by 2005, according to Strategies Unlimited. The forecast was revised downward to that figure from $1 billion to reflect this year's more conservative outlook.

"The big thing is that it is becoming clear that systems [companies] want to use tunable lasers; it just so happens that the tunable lasers they want to use are these ho hum, narrowly tunable devices, which is not very encouraging for companies working on the more exotic, widely tunable technologies," observes Hausken. "I think the narrowly tunable technology is going to get adopted pretty quickly."

"I think that it is a logical progression for some service providers and network equipment managers," says Jake Wiese, vice president of marketing at Bandwidth9. "The reason is that it is the most like what they have today. It does offer some of the economic advantages, but you don't have the tuning range and you don't have the tuning speed."

Widely tunable technology vendors may face more challenges during the Telcordia Technologies qualifications process, simply because these companies have adopted a range of technology approaches and much of the technology is new. In March, Agility announced that it had successfully met the Telcordia GR-468 CORE, the standard for fixed-wavelength lasers and that the company had results of some additional testing that ensures the reliability of their device's tunability. Agility is the first vendor in the widely tunable-laser component category to make such an assertion.

Which way to go?
Regardless of the qualification issues, systems houses are basing their tunable-laser decisions primarily on reliability, comparable performance to fixed-wavelength DFBs, and price, asserts Ron Nelson, president and CEO of Agility. Widely tunable devices are meeting these requirements, he says.

According to Nelson, several systems houses are seriously evaluating widely tunable technology for their next-generation products. "Three tier one systems houses have told us flat out, 'that's what we plan to do.'"

Bandwidth9, which focuses on tunable applications in the metro environment, has announced a joint development agreement with Metro-Optix (Santa Clara, CA, and Allen, TX), which is incorporating the MetroFlex tunable transmitter into its CityStream bandwidth-management platform, and a component agreement with Movaz Networks (Atlanta). "What you're seeing now is a recognition from the wide tunability vendors that reliability and qualification is important, and I think that is one of the necessary steps to wide-scale deployment," says Weise. "We are of course aggressively pursuing qualifications. We have worked with Telcordia, and we have the qualifications for our device type now established."

"At some point, the systems suppliers have to leap over to a new technology because the temperature tuning of narrowly tunable devices can't do all that much," says Strategies Unlimited's Hausken. "Every one of them has engineers looking closely at widely tunable technology. When it gets down to it, are they going to risk their next-generation design on this technology? Maybe not, they'll just keep looking at it for another year."

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