Tunable filter startup Ondax Inc. will have something to celebrate this Christmas.

Last week, the company signed its first volume purchase agreement with a tier-one customer, says president Chris Moser. He can't reveal the customer's name, or size of the order, but does say it amounts to a six-figure sum. The news will be announced in a few days.

Analysts seem impressed. "Getting any kind of order -- volume or otherwise -- for tunable filters is pretty amazing right now," says Lawrence Gasman, director of optical components research at Communications Industry Researchers Inc. "The things tunable filters are used for are fairly few and far between. Volume markets for these components simply haven't developed yet."

Most of the scenarios on which tunable filter companies have built their business plans have come crashing down, he says. One particular vision -- a reconfigurable network architecture, which uses tunable lasers along with tunable filters to enable flexible provisioning of bandwidth -- has been delayed to the point where no one is willing to bet on when it will take off (see Tunable Filters Go Solid State).

Another potential application -- for backup line cards -- is looking less attractive now that pricing pressure has started to mount. Originally, tunable filter vendors were expecting that they could sell their products at a considerable premium. That looks unlikely to be acceptable in the current market climate.

Ondax, to its credit, has managed to find an application outside these areas -- in optical monitoring of DWDM systems. Rather than building one monitor per wavelength, a tunable filter cuts costs by allowing one monitor to select between multiple channels.

The use of tunable filters in optical monitoring is not new -- optical spectrum analyzers (OSAs) such as those from Agilent Technologies Inc. (NYSE: A) employ tunable filter technology inside. However, such instruments are bench-top bits of kit selling for multiple tens of thousands of dollars apiece. Ondax's filter enables inexpensive, compact monitoring gear that can monitor networks in situ.

Moser declined to give a price for the filter but did note it would enable considerable savings, both in capex and opex, compared to the cost of using an OSA.

Ondax is not the only vendor trying to survive in the slim market for tunable filters. Other vendors include Aegis Semiconductor Inc., Auxora Inc., Cidra Corp. (Nasdaq: CIDC), Micron Optics Inc., NP Photonics Inc. (through its acquisition of Parvena/Solus - see NP Photonics Gets Compliant MEMS), Optoplex Corp. (see Optoplex Ships Tunable OADM), and Optune Technologies, a subsidiary of StockerYale Inc. (Nasdaq: STKR). And of course JDS Uniphase Corp. (Nasdaq: JDSU; Toronto: JDU), which makes just about everything, also has a tunable filter.

Every vendor has a different technology inside its filters. JDSU's part, for example, uses a piezo-electric driver to turn a standard thin-film filter though an angle compared to the incoming beam of light. The problem with that, Moser contends, is that positioning the filter requires complicated feedback and software to get a precise enough angular position.

JDSU spokesman Gerald Gotheil says Moser is referring to an old technology that has now been superceded. The new technology, introduced in November 2001, moves a "linear variable filter" and is voltage controlled.

Ondax's approach is based on what's called "3D Bragg gratings", which are a kind of hologram. "Holographic Bragg gratings are in many ways similar to Fiber Bragg gratings except that the recording medium for the grating is not a single mode fiber but a bulk medium," Moser explains. Ondax's filter contains 40 elements written on a lithium niobate chip, which are accessed by moving a collimator lens in front of the chip -- a technology that's similar to the read-write head in a CD player. The filter chip covers the whole of the C-band with 100GHz spacings.

The success of this technology depends critically on the reliability and reproducibility of the recording material, Moser says, noting that only a few groups in the world have developed reliable holographic material besides Ondax. He names Aprilis Inc. and Inphase Technologies Inc., which are both developing holographic data storage.

In fact, Moser contends that material reliability problems have all but killed optical switch startup Trellis Photonics (see Trellis: 'No Shut Down'). According to a report in Globes Online, Trellis fired 25 of its 35 employees this summer and suspended all business activities. Trellis did not respond to calls.

Ondax claims to have solved reliability problems with a proprietary material treatment of lithium niobate developed by the University of Osnabrück in Germany and the California Institute of Technology (Caltech) in the U.S.

Founded in July 2000, Ondax has received $7.5 million in funding from Alcatel Ventures, Corning Innovation Partners, Mellon Ventures, and others. The startup plans to raise a "small amount" of money to see it through to 2004, says Moser. It would need to need to reel in another four or five customers to see it through to breakeven, he adds.

— Pauline Rigby, Senior Editor, Light Reading