Following the light: Optical switches illuminate components space

The glory days of components and processors for the PC industry seem to have faded, with new chips released before many users get their new PCs out of the box. But recently, components for use in optical switches have spawned a flood of interest and money invested in photonics.

The new photonic switches promise to route light through optical cross-connects without electronics. But this non-electronic feature has created obsessions with photonic switches and another religious war for the telecommunications industry.

One of the first to support all-optical cross-connects was Lucent Technologies with its LambdaRouter, which scales up to 256 wavelengths. The LambdaRouter uses micro mirrors to direct light through the network.

Start-up Xros, which Nortel Networks recently acquired for $3.25 billion, also is focusing on the micro mirror technology, which can scale up to 1152 wavelengths (Telephony, March 20, page 8).

Another technology with the same mirror-method capabilities is Agilent Technologies' bubble-based system, developed from inkjet printer technology. That technology can switch 512 wavelengths, said David Anderson, director of R&D for Agilent's optical networking division (Telephony, March 13, page 9).

"We wanted to allow for modular scaling and fault containment," he said.

And by keeping the component at a 32-by-32 level, Agilent can confine faults to no more than 16 output or input. That also would theoretically enable a pay-as-you-grow model for service providers.

Avanex also is trying to tap the photonic switching space but will not reveal its switching method.

It has developed the PowerMux family of wavelength processors, which can handle any channel count, channel spacing and bit rate, said Ken Bystrom, senior engineer and manager of product development for Avanex. But instead of fitting into an optical cross-connect, the Avanex processor sits at the edge of the network in add/drop multiplexers.

"The PowerMux allows us to separate wavelengths down to 12.5, 25, 50 and 100 GHz," Bystrom said. PowerMux achieves 80% spectral efficiency in its use of the C- and L-bands, he said.

The Avanex processor is different because it's capable of uninterruptible express, Bystrom said, while the Agilent switch, for example, is matrix-based.

Service providers and vendors are purchasing the PowerMux, and according to Bystrom, MCI WorldCom is integrating the processor in to its equipment.

But as a whole, the technologies still need to incorporate the management functions of the components.

Vendors such as Ciena, Cisco Systems, Sycamore Networks and Tellium, which have electrical components in their optical switches, still are standing by electronics until the purely photonic switches are proven.

"The technologies have advantages and drawbacks, but they need to be proved stable over time and show some kind of cost advantage," said Joe Bass, vice president and general manager of Cisco's core optical transport business unit. "And that hasn't happened yet."

While service providers such as Qwest Communications are intrigued by all-optical networks, they also feel more comfortable with at least some electronics at this point. "While less and less is better, electronics do effectively perform certain functions for our network," said Ron Haigh, senior network architect for Qwest.

"The question is, are the networks really ready for the switch [to all-optical]?" said Jeff Dahlberg, technology analyst with Gilder Technology Group. "I'm not sure [they are], especially if they won't necessarily be more effective."

"Technology for technology's sake is interesting, but it just doesn't cut it-and these technologies simply have more work yet to do," Bass said.

Methods used for photonic switching

MEMS - micro-electro-mechanical systems use arrays of microscopic mirrors to reflect light from input port to output port

LCD - liquid crystal display uses liquid to bend the light

Ink-jet printer/fluidics - use heat to create bubbles in fluid channels that then reflect and direct light