Agere Favors Thin-Film Filters

It's ditched AWGs in favor of thin-film filters, which it will be displaying at OFC

March 6, 2002

3 Min Read
Agere Favors Thin-Film Filters

Agere Systems' (NYSE: AGR) announcement of a 50GHz mux/demux highlights the fact that the company is choosing thin-film filter technology over Arrayed Waveguide Gratings (AWGs) for wavelength multiplexing (see Agere Ramps Up 3D MEMS).

Until now, the consensus in the industry seemed to be that TFFs, AWGs, and a third alternative, Fiber Bragg Gratings (FBGs), all had their own application niches. But Agere's strong push into TFFs suggests that it now sees one of those technologies coming forward as an overall winner.

"Thin-film-filter-based passive technologies are less expensive thanfiber Bragg gratings or AWGs for 1x4, 1x8, and 1x10, the configurations mostin demand by customers," says Tom Christie, director of strategic marketing forAgere's optical core and metro networks division, in the press release issued today.

Originally Agere had both thin film and AWGs under one roof, but the company quietly ditched its AWG business about 18 months ago, according to Dan Wilt, product line director for components. "We had some issues with that component, and we haven't yet relaunched it," he says.

Could those issues relate to the fact that Agere's biggest customer was no longer buying its AWGs? Lawrence Gasman, an analyst with Communications Industry Researchers Inc. (CIR) seems to think so.

Agere had originally developed AWGs for internal consumption while still part of Lucent Technologies Inc. (NYSE: LU). But Lucent appears to go elsewhere for its AWGs now. According to Gasman, who is currently co-writing a big report on wavelength multiplexers, Lucent's main AWG suppliers are Hitachi Cable Ltd., NTT Electronics Corp. (NEL), and Lightwave Microsystems Corp.

Agere also realized that it was competing with itself, says Wilt. At medium channel-count numbers, AWGs and TFFs can each fit the bill, so Agere would not necessarily gain more customers by offering both types of product.

And Agere isn't the only company to back away from AWGs recently: Nortel Networks Corp. (NYSE/Toronto: NT) also killed its AWG development work (see Nortel Nixes Passive Components). Nortel, however, doesn't makes its own TFFs, but these are a commodity product on offer from dozens of vendors, including JDS Uniphase Inc. (Nasdaq: JDSU; Toronto: JDU) and Oplink Communications Inc. (Nasdaq: OPLK).

Agere outlines the advantages of TFFs over AWGs in its press release. In a nutshell, TFFs have better insertion loss, crosstalk, and stability with temperature than AWGs, it claims. A typical figure for insertion loss is 3.8 dB, it claims. For comparison, AWGs vary between 4.0 dB and 8.0 dB, depending on the vendor and the application they have been designed for. And only the products with losses at the higher end of the range have optical passband characteristics as good as TFFs, Agere notes.

Against TFFs is the fact that they are more complicated to assemble and package than AWGs. Nevertheless, Agere claims the cost of producing them is still much lower.

It should also be kept in mind that AWGs are a lot more than just another way of splitting and recombining wavelengths. They're a starting point for making a wide range of integrated optical components such as mux-variable optical attenuators, optical channel monitors, dynamic gain equalizers, and optical add/drop multiplexers (see Photonic Integrated Circuits).

Agere's 50GHz mux/demux component, called the W7500, is available now in both samples and production quantities. It rounds out Agere's product range, which also includes 100GHz and 200GHz versions. The new device will be showcased in a live demonstration at the Optical Fiber Communication Conference and Exhibit (OFC).

— Pauline Rigby, Senior Editor, Light Reading
http://www.lightreading.comFor more information on OFC 2002, please visit:

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