ANAHEIM, Calif. -- OFC 2002 -- Vitesse Semiconductor Corp.'s (Nasdaq: VTSS) announcement last week of an optical transponder caused industry watchers to do a double-take: Vitesse, a chip maker, announcing optical products? (See Vitesse Releases Transponders.)

No, it wasn't a mistake. In fact, Vitesse has followed up last week's news with an announcement today (Monday, March 18) of an all-optical switching fabric (see Vitesse Demos Switch ).

Both products were developed by Versatile Optical Networks, a startup that Vitesse acquired last year (see Vitesse Acquires Versatile).

What's more, unlike many of the companies that were bought in the recent past, Versatile appears to be thriving under its new ownership. Not only is it announcing new products, but some of those products are already in full production.

Vitesse will demonstrate the new products at the Optical Fiber Communication Conference and Exhibit (OFC), starting tomorrow.

So, what's the link between switch fabrics and transponders? According to Amit Jain, a founder of Versatile and now VP and general manager of Vitesse's optical systems division, Versatile originally started out developing a complete optical add/drop multiplexer (OADM) subsystem. "You need the optical switches and the transponders to work together in this application," he notes.

"But," says Jain. "Our customer reaction was, 'We like your switch and your transponders, but we don't want the complete subsystem. We want to build our own line cards.' " So Vitesse decided to sell the parts separately.

Ready for some details?

VIT10 Transponders

The transponder family, called VIT10, is targeted at 10-Gbit/s line rates and long-haul applications above 80 km. It's form factor is compatible with the 300-pin multisource agreement for OC192 DWDM transponders, measuring 3.25 inches wide by 4.0 inches long by 0.53 inches high. Jain claims that's one of the smallest form factors in the industry for a long-haul transponder.

Where Vitesse adds value to the product, he contends, is in high-performance optical components -- Versatile developed its own laser, modulator, and receiver packages. As a result, the transponders give better overall system performance. For instance, he claims that the improved receiver sensitivity at 10 Gbit/s gives an increase in system margin of 6 dB. This means light can go farther before it needs amplifying.

Already in full production, the first member of the product family is called VIT5000. This particular device is multirate, handling several speeds up to 10.7 Gbit/s, which allows it to encompass OC192 Sonet, OC192 Sonet with digital wrapper, and 10-gigabit Ethernet. It has analogue control interfaces.

Vitesse has also developed a version of this module with digital control interfaces, called the VIT5100. It is currently in pre-production.

A third member of the family, called VIT5101, has not been announced yet, but will be on show at OFC. This module is essentially the same as VIT5100, except that it can reach data rates of 12.5 Gbit/s, allowing customers to use it for proprietary forward error correction (FEC) schemes, such as Vitesse's own SuperFEC chips. Such schemes require more overhead than standard FEC but give better system margin overall.

Finally, there's VIT5300, also in full production, which is a so-called "laserless" module. It's based on the VIT5000 with one key difference -- there is no laser inside. While this might sound a bit strange, Vitesse hopes it could be just the ticket for systems integrators building line cards using Tunable Lasers. Tunable lasers are just light sources and need additional electronics and control circuits around them. Vitesse's module, Jain says, offers systems integrators a easier solution than building all the extra stuff onto a line card separately.

VOS Switching Fabric

Vitesse's optical switching fabric isn't actually MEMS (micro-electro-mechanical system), but it's based on something that works in the same way as 3D MEMS, according to Jain. It uses two banks of tiny tilting mirrors to switch light between different ports.

Rather than being sculpted out of a single piece of silicon, as MEMS components are, the Vitesse fabric is assembled from different materials. It uses mirrors, hinges, and a sensor that automatically adjusts the position of the mirrors.

The upshot is a switch with much lower insertion loss, Jain claims. Vitesse has already tested the mirror elements through 10 million switching cycles and finds that they have a worst-case insertion loss of 3 dB at the end of life. The reason for this, he says, is because it's possible to create larger, higher-quality mirrors with Vitesse's approach, than is possible with ordinary MEMS.

For comparison, leading MEMS vendor OMM Inc. offers a comparably sized switch (16x16), albeit one based on 2D rather than 3D MEMS, with worst-case insertion loss of 6 dB, according to datasheets posted on the company's Website. (Smaller switches have lower insertion losses but are not appropriate for comparison.)

The position sensors are important too. By having sensors built into the hinges of the mirrors and optical feedback, Vitesse avoids the need for active alignment during the manufacturing process. It also helps make the switch more robust. "You can shake the box up and it will put itself right," he claims.

Indeed, Vitesse has tested the mirror components -- it has yet to test the finished subsystem -- to Telcordia Technologies Inc. specifications, including vibration and shock tests. It passed all tests with flying colors, Jain claims, except for the drop test. "There is a limitation on the drop test. We will not be able to drop the mirrors 12 inches onto concrete, we have to limit that to 4 inches." [Ed. note: That's no way to treat an expensive optical instrument!]

Vitesse offers the switch in two configurations: an 8x8 protection switch, which comprises an 8x8 switch fabric with an array of 2x1 switches on the input ports and an array of 1x2 switches on the output port; and a plain 16x16 crossconnect. The 8x8 switch is already in production and shipping to customers, according to Jain. The 16x16 version is slated to sample in Q2. Telcordia testing should be completed by May and August, respectively.

For more detail on recent developments in transponders and MEMS switches, please visit: www.nottheofc.com

— Pauline Rigby, Senior Editor, Light Reading
http://www.lightreading.com