Sabeus Photonics Inc., a company working a number of new technologies used to manipulate light, announced this week that it has closed a third funding round worth $16 million. The company's investors, old and new, include Agere Systems (NYSE: AGR), Redpoint Ventures, Digital Coast Ventures, TL Ventures, and Credit Suisse First Boston.

The designer and maker of optical components has raised about $24 million since it was founded in 1998, and it already has several customers, including Marconi PLC (Nasdaq/London: MONI) and Alcatel SA's (NYSE: ALA; Paris: CGEP:PA) Submarine Networks unit, for its passive components.

Sabeus, however, doesn't want to be known as just another passive components shop. The company hopes that with several patents and a photonics brain trust, it can eventually be viewed as a company that dramatically simplifies how optical components are made, without sacrificing component performance.

So far, Sabeus has been shipping products such as gain-flattening filters (used to get equal amounts of amplification over a range of wavelengths in an optical amplifier) and fiber-based pump laser stabilizers (used in Erbium Doped-Fiber Amplifiers (EDFAs) and Raman Amplification) for about a year and a half.

Next year, the company says, it will use techniques such as "mode coupling" and "cold writing" to make products like dynamically tunable filters, bandpass filters, and other components.

A Tutorial

Sabeus broadly defines mode coupling as a way to force light to react inside or between fibers in a very specific way. This could mean causing the light traveling through a fiber either to jump to adjacent fibers, chips, or waveguides through the side of the fiber, or to interact with itself within the fiber. By changing the index of refraction at the fiber's core, the light moves off axis and heads either into the fiber's cladding or into free space. When this happens, the light can be used to accomplish a specific signal processing task such as filtering, multiplexing, demultiplexing, Optical Modulation, or Optical Amplification.

The company says its expertise at controlling light inside the fiber is what enables its long-period Fiber Bragg Gratings (FBGs) to be very accurate filters. In 2002 Sabeus plans to make a very low-cost optical amplifier for the metro market by mode-coupling light from a fiber into adjacent chips, where the light would be amplified.

Sabeus defines cold writing as the capability to engrave onto the core of an optical fiber right through the outer cladding -- as opposed to mechanically stripping the fiber, etching it, then recoating the fiber. This technique cuts down on the cost of component packaging, speeds up the grating fabrication process, and results in stronger components, according to Dmitry Starodubov, Sabeus's cofounder and chief technology officer.

Cold writing came from Starodubov, who, along with E.M. Dianov, discovered that long-wavelength (330nm) ultraviolet light could alter the refractive index of a glass fiber without having the fiber absorb the light, as it would with mid-UV light.

With all the tricks it will use to make components manufacturing simpler, Sabeus must be careful not to introduce new problems or complexities, says Mikhail Zervas, technical director of grating design at Southampton Photonics Inc. "To get two fibers to 'talk' to one another through mode coupling, you have to take the polymer coating off. If you wrote through the coating at first without removing it, doesn't that put you right back to square one?"

Less Is More

It appears that Sabeus had originally planned to announce an $18.5 million funding round instead of a $16 million round, according to a report in Private Equity Week. A draft of Sabeus's early press release, obtained by Light Reading, shows that Anthem Ventures was originally listed among the investors, then later removed in the final draft.

Not to worry, say Sabeus representatives. They say the company closed the round at $16 million and, due to lots of investor interest, it may announce a second closing of the Series C round sometime soon. The report in Private Equity Week, however, quotes Sabeus CEO Andre de Fusco as saying that Sabeus would likely be profitable in 2002 and probably won't need another round of private capital.

- Phil Harvey, Senior Editor, Light Reading
http://www.lightreading.com