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Technology Stocks : Optical Networks and Components, DWDM and Tunable Lasers -- Ignore unavailable to you. Want to Upgrade?

To: Mike Hardy who wrote (182)	3/5/2000 9:04:00 AM
From: J Fieb	Read Replies (1) \| Respond to of 275

Here is the link.. lw.pennwellnet.com Registration is free, but I can't log in today. Chorum Makes A (Small) Splash In Optical Switches All Wet lightreading.com -------------------------------------------------------------------------------- It's easy to see why Chorum Technologies Inc chorum.com decided to announce its latest developments in optical switches based on liquid crystal technologies last Wednesday (March 1). If it had waited to unveil them at the Optical Fiber Communication (OFC) exhibition in Baltimore next week, they wouldn't have made much of a splash. Why? Because the products Chorum is launching - a Fast Add/Drop Switch, an 1x2 Optical Switch component and a Dynamic Variable Attenuator (a device for adjusting signal strengths in adjoining wavelengths) - aren't exactly cutting edge, according to industry experts. They say Corning Inc. corning.com is still way ahead of Chorum, having already demonstrated a 40 channel add-drop mux based on liquid crystal technology. Corning is now working on an 80 channel version, they add. Some optical switch vendors are also dubious about liquid crystal technology, saying it's unproven. And so far, none of the technologies being touted for "all-optical" switches can scale to the thousands of ports required by carriers. Also, none of them can switch light from one port to another at nanosecond speeds - something that will be needed for gear to route traffic on a packet-by-packet basis, rather than simply speeding up the provisioning of wavelengths. As Chorum will be far from alone in unveiling all-optical switching developments at OFC Let's start with explaining how liquid crystal switches work. Essentially, it's a two part process. First, the switch changes a property of the incoming stream of light such as its polarization or strength. Second, the light is fed into a passive optical device that steers it in different ways depending on its polarization, strength or whatever. The first part of the process is where the liquid crystals come in. It's the same technology that's used in laptop screens, where the shape and thus the optical properties of polymer molecules on each pixel can be changed by applying an electrical current to them. The big advantage of liquid crystal technology is that there are no working parts, so it's unlikely to wear out over time. It also has the potential to scale to quite a large size. (Laptop screens, for instance, are about 1,000 by 800 pixels.) However, vendors haven't been able to exploit this potential so far. As noted, Corning's 40 channel add drop mux is considered to be ahead of Chorum's developments on this score. One of the snags of liquid crystals has been slow switching speeds. "Traditionally, liquid crystal technology was difficult to use in telecommunications because it got viscous at low temperatures, resulting in poor performance and switching speeds," says Doug Dickerson, Chorum's vice president of marketing and business development. To speed up the signals, developers used heaters and special electronics, making solutions costly and cumbersome. Chorum, he says, has patented a technique that delivers millisecond switching without these measures. "We are the first to achieve this," he declares. PREVIOUS NEWS ANALYSIS MARCH 03, 2000 Tilting and Bending -------------------------------------------------------------------------------- One millisecond is viewed by vendors as a goal for protection switching - automatically switching light onto another fiber in the event of a failure of some sort. However, one millisecond is already the standard with mechanical devices sold by component vendors such as JDS Uniphase jdsu.com. These mechanical devices work on the basis of moving prisms or lenses to deflect light from one port to another. Their big advantage over liquid crystal equivalents is that they're well proven. They're in use in about 80 percent of all optical cross connects. Thermo-optical devices are also in widespread use in optical cross-connects. Fundamentally, these work by passing light through silicon or polymer which is heated up and cool down by electrical coils. This changes the material's refractive index to bend the light down one fiber or another. Like liquid crystal switches, they have no moving parts. But nobody has been able to build a large scale switch with them, and they have switching speed limitations. So far, the largest scale optical cross-connects have been made with micro-electro-mechanical (MEM) devices, arrays of microscopic mirrors than can be tilted to deflect light to different ports. The LambdaRouter from Lucent Technologies has 256 ports (see Optical Illusions ) and the TransXpress Optical Service Node will boast 512 ports one day (see Siemens Launches Optical Cross Connect ?Solution? ), but both boxes are prototypes at present. Astarte Fiber Networks, a part of Texas Instruments ti.com, says it's had a 72-port MEM-based switch since 1996, and that it's in use by MCI Worldcom Inc. wcom.com. Folk that have seen it, however, say it's huge - a 2-meter cube. Finally, it's worth noting that tunable lasers may end up replacing traditional cross connects. Some of the latest developments from startups such as Altitun Inc. altitun.com can switch light from one wavelength to another in a matter of nanoseconds. Lab experiments and carrier trials using these developments will be described at the OFC conference (see Researchers Unveil All-Optical Advances ).