Optical Switch Comes Into the Light
Some significant developments in optical switch modules and subsystems are tucked away in today’s announcement of product shipments by Optical Switch Corp. (see Optical Switch Ships Products).
The startup has emerged from stealth mode with a couple of families of optical switches that have much lower losses than existing products targeting similar applications. They also boast a number of other advantages such as synchronized protection switching, high repeatability, and wavelength independence.
Optical Switch has achieved this by putting the horse before the cart, according to Gary Nabhan, its president and CEO. Rather than starting with a technology and looking for applications, it’s identified requirements and then found technologies to address them, he says.
The startup’s Fiberkey family of switches demonstrates the point. These modules, which range in size from 1x2 to 8x8, have a couple of applications. The ones with more output than input ports can be used for protection switching, while the ones with equal numbers of input and output ports provide "an extremely competitive" building block for add-drop multiplexers, according to Jeremy Chappell, Optical Switch's VP of business development.
The key requirements for such switch modules are low loss, low switching speed, high reliability, and the ability to switch a whole bunch of wavelengths at exactly the same moment.
The Fiberkey products achieve this by using "frustrated total internal reflection" -- a phenomenon that the fish among you will be familiar with. When fish aren't perusing Light Reading, many of them scan the bottom of the ocean by looking upwards at its reflection beneath the sea’s surface (that's why their eyes are often on the top of their heads). This reflection is blanked out, or “frustrated” by the underside of boats.
The same effect is achieved using “evanescent couplings” in Fiberkey modules. “We were the first to think of it as a method of optical switching,” says Nabhan. Two plates are separated by a small gap or brought together, shifting the reflective surface from one to the other in a way that bounces beams of light to different outputs. This is all on a very small scale. A 4x8 module only measures 35mm x 30mm x 9mm.
As a single pair of plates can shift multiple beams of light, synchronized backup is assured. “Nobody else has a synchronized 4x8 protection switch,” says Nabhan.
The technology also delivers very low insertion losses -- less than half a decibel for a 1x2 switch and less than one decibel for a 1x4 switch.
The availability of low-loss switches like this “removes a key barrier” preventing the more widespread application of optical technologies in telecom networks, according to Cindana A. Turkatte, VP of marketing at Iolon Inc.. Iolon has also developed a low-loss switch module, but has shelved the project temporarily while it focuses on tunable lasers (see Corning Backs Laser Startup and Corvis's Secret Sauce?).
Fiberkey products also have low switching speeds (one millisecond) and low power consumption (less than one watt) and promise high reliability, according to Chappell. “There are no exotic materials. What is exotic is the design,” he says.
Optical Switch’s other product family, Kaleidoscope, targets two other applications. One group of modules with one input port and up to 128 output ports can be used in conjunction with measuring equipment to monitor signals in multiple wavelengths, in a DWDM (dense wavelength-division multiplexing) system, for instance. Another couple of modules has an equal number of input and output ports -- 16x16 or 32x32 -- and can be used to build optical crossconnects.
In both cases, the fundamental technology is described as “free-space conformal optics with closed-loop control circuitry” by Nabhan. Essentially, light is bounced around by mirrors in a way that avoids needing collimation -- the focusing of light beams using special lenses -- which would mean that the devices wouldn’t be wavelength independent.
The other key point about Kaleidoscope’s technology is its repeatability. When it’s used to monitor various wavelengths in a DWDM system, there’s no risk of the readings being skewed depending on the position of the wavelength, as there is with today’s mechanical devices, according to Chappell.
Optical Switch says samples of its Fiberkey modules have already been shipped to a number of customers and it’s already earning revenue on its Kaleidoscope products. Fiberkey modules cost upwards of $600 apiece and Kaleidoscopes cost upwards of $4,500.
Optical Switch has kept a low profile since it got started in 1997. It now has 150 staff in two locations – Richardson, Texas, and Bedford, Mass.
So far, Optical Switch has raised a total of $58 million. “We haven’t accepted capital from conventional VC funds," says Nabhan. Backers include ADC Telecommunications Inc. (Nasdaq: ADCT) and crossover investors such as KMF Partners LP, Petros Capital LLC, Putnam Investment Management Inc., and Tudor Investment Corp..
Nabhan says he’s about to start raising a final private round of finance, which he hopes to close within a few months. After that, who knows? Maybe Optical Switch will become a hot prospect for an IPO.
-- Peter Heywood, international editor, Light Reading http://www.lightreading.com