Agility Unveils Long-Haul Laser
Competition among developers of widely tunable lasers is hotting up, judging by an announcement that Agility Communications Inc. plans to make next Monday (April 2).
The startup says it will unveil “the first packaged prototype of a truly monolithic 10 milliwatt widely tunable laser that can rapidly tune to more than 90 ITU channels” -- a development that marks a couple of significant milestones.
First, this a big boost in power. Agility’s first tunable laser, the Agility 3040, delivers a maximum of 4 milliwatts, which limits its applications to the shorter routes found in metro networks (see Agility Launches First Product).
Boosting the power to 10 milliwatts will enable Agility to start tackling the long-haul market, according to Arlon Martin, Agility’s vice president of marketing. This will bring it into competition with companies such as Iolon Inc. and New Focus Inc. (Nasdaq: NUFO), which are making more expensive, more powerful external cavity lasers.
Agility’s developments also mark an integration milestone. The company has achieved this boost in power by adding an amplifier section to its existing four-section SG-DBR (superstructure grating distributed Bragg reflector) tunable laser (see Tune In! for more on SG-DBRs). The whole thing is developed on the same piece of indium phosphide.
This is much more than a clever demonstration in a lab, according to Martin. Agility has made the laser and amplifier combination and has packaged it on its regular production lines, he says. In other words, it’s relatively close to being a mass-produced commercial product.
Making a complete laser on a single piece of indium phosphide costs a lot less than assembling an external cavity laser (ECL) from three or more chips made elsewhere, the approach taken by Iolon and New Focus, according to Martin.
Iolon, however, points out that there are advantages to its approach. Iolon is in a position to buy best-of-breed chips, while Agility is stuck with whatever it can make itself. “Power isn’t everything,” adds Cindana A. Turkatte, Iolon’s VP of marketing. Other issues such as spectral fidelity are also important and depend on using the best components wherever they're made, she says. She questions whether Agility could achieve the same quality of light transmissions as Iolon with its approach.
"I would argue that [Agility's] process is lower cost, but it's at the expense of performance," says Tim Day, a founder and CTO of New Focus. "A semiconductor optical amplifier will add noise to a laser," he adds, noting that it's a "big penalty to pay" in long-haul networks, where the signal-to-noise ratio is so crucial.
Day also points to other problems with Agility's approach. Adding an amplifier means that the whole assembly needs four different electrical currents to operate. This raises reliability concerns, he says. The ageing mechanisms of lasers needing three currents aren't well understood, so adding a fourth current could make matters worse. ECLs are controlled by a single current, he adds.
Finally, Day says that Agility's design results in tradeoffs among power, light coherence, and tuning range. All three can't be optimized at the same time, as they can with ECLs, he says.
Turkatte suggests that Agility is hyping its ability to penetrate the long-haul laser market because it's having trouble finding customers in the metro market. “We’ve had a lot of their customers come to us,” she says.
Right now, none of these companies are actually shipping commercial products, so the jury's still out on who's got the best tunable laser, and who's blowing smoke. The chances are they'll find different niches.
-- Peter Heywood, international editor, Light Reading http://www.lightreading.com