New technology offers alternative to WDM and SONET

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Valerie C. Coffey

Centerpoint Broadband Technologies, Inc. (San Jose, CA) has revealed a working alternative to traditional Synchronous Optical NETwork (SONET) and WDM technologies. The company announced its subcarrier multiplexing (SCM) technology Aug. 28 at the National Fiber Optics Engineers Conference (NFOEC; Denver, CO). With SCM technology, multiple digital signals are aggregated into one modulated radio frequency (RF) signal, which is sent at one wavelength onto a single optical channel (see figure). The SCM technology is compatible with both 100 GHz and 50 GHz DWDM and SONET systems. The SCM technology is an alternative to existing networks, but can also be deployed over existing SMF fiber hops to complement DWDM and SONET systems. This allows flexibility between network architectures with the reliability of SONET and the capacity of DWDM at a fraction of the cost, said Centerpoint officials.

"We`re using advanced RF-modem technology at a higher speed to achieve greater capacity in the same bandwidth," said Eric Schmidt, director of business development at Centerpoint. The SCM technology is frequency-domain driven, whereas SONET operates in the time domain and WDM in the wavelength domain. Partitioning fiber capacity in frequency instead of time solves pulse rate limitations, or how quickly lasers can pulse a signal down a channel. The SCM technology is derived from the more mature communications field, where proven digital circuitry has evolved in the fields of wireless, satellite, and copper cable. Data rates of 20 Gbit/s per wavelength can be achieved.

At the NFOEC show, Centerpoint also unveiled its Lightwave Efficient Network Solution (LENS). The LENS hardware reduces the number of network elements needed to aggregate multiple signals into a single wavelength, without retrofitting the existing network.

"With the rapid adoption of cable modem and digital subscriber line technology, the bottleneck in the network is moving from the `last mile` to the metro area network, or `next to the last mile,` " said Dana Waldman, president and CEO of Centerpoint. "LENS creates a system that fits into virtually any regional or metro network topology. This allows carriers to take full advantage of spectrum efficiency in a single package."

Centerpoint Broadband recently received more than $7.5 million in investment capital from MKG-SBC Investments, bringing the total private equity raised by the company to more than $67 million. For details, contact guribes@centerpoint.com Wdm93921 7

With subcarrier multiplexing technology, partitioning fiber capacity by frequency instead of time solves common pulse rate limitations related to how quickly lasers can pulse a signal down a channel.

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