AON Unveils Strange Wavelength Mux
The box, called MetroScout, is a wavelength multiplexer, but it bears little resemblance to the conventional ones used in today’s telecom networks, which are typically based on thin-film filters or arrayed waveguide gratings (AWGs). It puts a mere four wavelengths over a single fiber, only operates over short distances, and uses 1310 nanometer lasers rather than the 1550nm ones used in most DWDM (dense wavelength-division multiplexing) gear.
The bottom line? Massive cost reductions. 1310nm lasers cost about $40 apiece compared to $2,000 for a 1550nm DWDM laser, according to Ralph Bennett, AON's president and COO.
AON says its platform will significantly enhance the capabilities of existing 1310nm equipment. It's pitched at the edge of the network, where carriers still use a single channel at 1310nm to move data over short distances. And that’s just for starters. The MetroScout’s biggest strength, according to Bennett, comes from the way it squashes four wavelengths down a fiber at 1310nm. It uses all-optical wavelength conversion to shift the wavelengths slightly, so they don’t overlay and interfere with each other. That means that the box is bit-rate and protocol transparent up to OC192 (10 Gbit/s), a boon when it comes to upgrade time. (Above OC192, fiber transmission issues start to degrade the performance.)
The drawback of using 1310nm lasers is that they limit the reach of the link: The signals cannot be amplified by erbium-doped fiber amplifiers (EDFAs). As a result, MetroScout has a maximum reach of 25 kilometers, says Bennett.
While the ability to do all-optical wavelength conversion is exciting, it's not clear yet if carriers are ready for all-optical products, says Christopher Janz, an expert on wavelength conversion with Akara Inc., a startup developing optical access network equipment.
The current method of doing wavelength conversion is to use optoelectronic transponders, which are becoming cheaper all the time. "Optoelectronic transponders [are] a tough alternative to beat, up to 10-Gbit/s operating rates," says Janz.
Another consideration is the fact that it is often necessary to turn signals back into electricity in order to extract information such as error checking and management overhead. Right now, this cannot be done optically. "With this in mind," Janz says, "I would be inclined to view the use of all-optical devices as more 'science fair' hype than serious endeavour, at least in applications with line rates up to 10 Gbit/s."
Bennett won't give any clues about how the company does its all-optical wavelength conversion, except to say that it was a spinoff of development work in progress on its photonic transistor -- an all-optical equivalent of an electronic transistor.
A photonic transistor also sounds like "science fair" stuff. AON says it’s demonstrated the ability to switch light with light, with a switching speed of a few femtoseconds, using something based on holograms. Whether this will prove to be a true equivalent to the electronic transistor remains to be seen.
— Pauline Rigby, Senior Editor, Light Reading, http://www.lightreading.com
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