Blue Sky Scores Four in a Row
First it launched a low-cost pump laser for erbium doped fiber amplifiers (see Blue Sky Announces EDFA Pumps). Then this week the company unveiled a high-power tunable laser that contains no moving parts (see Blue Sky Intros Programmable Laser).
Two more announcements are on the horizon, it says. Next week the company will unveil a MEMS-based optical crossconnect and, shortly after that, a family of lasers for optical wireless systems.
All this puts Blue Sky in a stronger position than many component startups, which often enter the market with narrow product portfolios, sometimes based on a single product. But then, Blue Sky is not a traditional telecom startup.
"Our claim to fame is the microlens," says Dan Hu, Blue Sky's president and CEO. "It takes 97 per cent of the light from the laser and converts it [from an elliptical beam] into a perfect round shape. It can also correct astigmatism and other aberrations." (See a picture of a microlens at http://www.blueskyresearch.com/products/p_uLens.html). This process results in light signals being stronger than would otherwise be the case.
The company started off selling its microlenses in two markets: data storage, where it is used for focusing energy to write on recording media; and the construction industry, for laser range-finding and alignment of pipelines and other large structures.
Blue Sky is now pursuing opportunities in telecom. Though the new crop of products might seem unrelated, the microlens technology is the common thread.
Two of the products -- the pump lasers and free-space optics sources -- rely entirely on microlenses to give them an edge. But the tunable laser and MEMS crossconnect also contain other patent-pending innovations, says Hu. Here are the details:
EDFA pump laser
Blue Sky reckons it will be able to sell its laser so cheaply that it will enable EDFA (erbium doped fiber amplifier) manufacturers to drop the cost of EDFAs below the $1000 price mark. Right now, Blue Sky has announced a 980 nanometer pump laser with 50 to 120 milliwatts of output power. Higher-power lasers (up to 200mW) will be available later this year, and 1480nm lasers and Raman pumps are in the works.
As noted, the microlens is the key element. For a start, since the microlens collects almost all the light emitted by the laser, there's no need to push the chip so hard, so it runs cooler. That makes it possible to use simple TO-can packaging.
Costs also come down because yields are high, says Hu. Dud chips can be thrown out early in the process because burn-in of the laser takes place before the laser is aligned and packaged. In traditional telecom lasers it’s the other way round -- the burn-in has to take place after the laser chip is welded to the fiber. There's no point doing it sooner, because the laser welding process can shift the alignment by an unacceptable 5 or 6 microns. Using a microlens does away with the low-yield laser welding.
Blue Sky is the third vendor to announce a tunable laser capable of 20mW of output power (see Iolon Unveils Tunable Laser and New Focus, New Laser). The three products have one thing in common -- an external cavity. But unlike the offerings from Iolon Inc. and New Focus Inc. (Nasdaq: NUFO), Blue Sky's laser's got no moving parts, it claims. That could be a big attraction to systems vendors who are worried that moving parts are not robust enough.
Hu won't reveal anything about the tuning mechanism, except to say it's based on electro-optics and it's fast, possibly nanoseconds. It's the subject of a patent application that hasn't yet been approved, he notes.
He adds that the laser is very small. The prototype will fit in a one-by-one-inch butterfly package, and Blue Sky hopes to reduce the footprint to one inch by half an inch.
Blue Sky calls its laser a programmable transmitter because it tunes in discrete steps to wavelengths on the International Telecommunication Union (ITU) grid. The wavelength locker -- the widget that locks onto the ITU grid -- is also the subject of a patent. It's a temperature-independent etalon (or cavity). "The trick is [to make it] so if any part expands, another part expands in the opposite direction. The net change [in the length of the etalon] is zero," Hu explains. As a result, thermal control of the package is not required (though it's still needed for the laser chip).
Like many of vendors of optical switch cores, Blue Sky is using tiny mirrors that tilt in two directions (see Optical Switching Fabric). It plans to make arrays up to 64x64 and then use these as building blocks to make larger switch sizes.
The mirrors themselves are made from single crystal silicon, and are magnetically actuated. Blue Sky claims that this gives much better performance and reliability than electrostatic actuation, which is the approach favored by most other vendors -- with the notable exception of Integrated Micromachines Inc. (see Switch Startup Raises MEMS Questions).
"Electromagnetic forces are much stronger [than electrostatic forces], but most important, it's linear," says Hu. In other words, double the applied current, and the mirrors move through twice the angle. That makes the control software a lot easier to implement, he says. In fact, Hu reckons that the complexity of the control software is a key reason why MEMS switches haven't been deployed yet.
So where are the microlenses in this application? "One of the complexities of optical switches is how to align thousands of lenses," says Hu. Blue Sky has a patent on a "cross lens" that alleviates the problem, he claims. It's a lens with a semicircular cross section, like half a pencil. These are arranged in horizontal and vertical rows, so that they cross in a trellis. Every intersection of two lenses behaves like a single collimating lens. "So now, instead of needing to align NxN lenses, we only need to align 2N," he adds.
Free-Space Communications Lasers
Despite being announced last, this product is the most natural extension of Blue Sky's non-telecom applications. After all, if it's possible to send beams alongside pipelines, then sending them from building to building shouldn't present a problem. According to Hu, Blue Sky's laser delivers an almost perfect wavefront -- thanks to the microlens -- which suffers less from distortion as it travels through the air. "A recent test showed that four times the laser power arrived at the detector under fog conditions with our lasers as compared to the competition… even though all the transmitters start out at the same optical power," he claims.
Blue Sky says it has a customer already buying its free-space communications laser in volume, but it won't say who.
— Pauline Rigby, senior editor, Light Reading http://www.lightreading.com