ITU sets standard for metro networks

The International Telecommunication Union (ITU) has set a global standard for metro "optical fiber" networks that will expand the use of Coarse Wavelength Division Multiplexing (CWDM) in metropolitan networks.

This standard, the ITU said, is necessary to meet the increasing demand of voice, data and multimedia services for low-cost, short-haul optical transport solutions. It is also expected to produce savings for telecommunications operators, which hopefully will passed them on to consumers.

The worldwide "optical metro network" market will increase from $1.1 billion in 2001 to $4.3 billion by 2005, according to a recent report by Gartner DataQuest.

Bolstered by this new standard, CWDM is poised to capture a substantial share of this market. CWDM applications are especially good for coverage of up to 50 kilometers.

"Where the distances are shorter and the need for capacity is less, CWDM applications are able to use wider channel spacing and less expensive equipment, yet achieve the same quality standards of long-haul optical fiber systems," says Peter Wery, chairman of ITU-T Study Group 15.

Dense WDM optical systems, which carry a large number of densely packed wavelengths, require a thermoelectric cooler to stabilize the wavelength emission and absorb the power dissipated by the laser. This consumes power while adding cost.

However, for short transmission distances, a "coarse" wavelength grid can reduce terminal costs by eliminating the temperature control and allowing the emitted wavelengths to drift with ambient temperature changes.

"This standard will be a stabilizing force for manufacturers of filters with wide channel spacing, for manufacturers of uncooled lasers with an expanded number of wavelengths, and for system manufacturers looking to offer low-cost, short-haul optical transport solutions. Taking all this together, a well-defined grid will increase the rate of CWDM product and market development," Wery said.