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Alcatel-Lucent Driving Fast Optical Nets
[March 30, 2007]

Alcatel-Lucent Driving Fast Optical Nets

TMCnet Web Editor
This week’s OFC/NFOEC conference in Anaheim gave telecom Alcatel (News - Alert)-Lucent the stage to present several papers the telecom giant is conducting in an effort to develop future high-speed networks able to transmit voice, data, and video signals.

The company envisions future optical networks transmitting higher and higher amounts of data—in many terabits per second—over optical fiber. This would make it possible, for instance, to transmit data from more than 600 DVDs per second.
In one project, Alcatel-Lucent's Bell Labs researchers in New Jersey successfully transmitted ten closely spaced 100 Gbit/s WDM data channels over a 1,200 kilometer optical transmission distance in a systems experiment that included six optical add/drop nodes like those used in today's transparent mesh networks. Using this design, the researchers achieved a spectral efficiency of 1 bit per second per Hertz (b/s/Hz) over the 1200 Km distance using only a single polarization of light.
According to the company, these results demonstrate the practicality of effectively doubling the throughput of today's commercial optical networks, using WDM channel spacing typical of existing and deployed 40G networks.
Researchers at Alcatel-Lucent's Research and Innovation center in Paris presented a paper on using coherent detection to contain distortion and dispersion which happen when sending WDM channels at 40 Gbit/s rate over links designed for 10 Gbit/s rate. The use of coherent detection instead of conventional direct detection paves the way for techniques such as using polarization division multiplexing on top of wavelength division multiplexing. This would make it possible to generate data at 40 Gbit/s with just 10 Gbit/s rate.
Researchers at Alcatel-Lucent’s Bell Labs in New Jersey demonstrated the ability to receive and convert serial 107 Gbit/s optical data into lower rate data streams with the first fully integrated 107 Gbit/s demultiplexing optical receiver. This optical receiver integrates a 100 Gbit/s photodetector with a 1:2 electronic demultiplexer in a single package. At such high speeds, integrating the parts provides for better performance compared to having separate photodetector and demultiplexer modules. The company considers this a significant step towards the commercial realization of 100 Gbit/s serial transmission systems.
In a fourth paper, Alcatel-Lucent's Research and Innovation researchers from Stuttgart demonstrated the Wavelength Division Multiplexing (WDM) transmission of 10 channels, each carrying 107 Gbit/s bit rate information over 480km. After a recent single-channel demonstration, this is reportedly the first WDM transmission of channels based on serial binary modulation format exploiting full Electronics Time Domain Division Multiplexing (ETDM), both at the transmitter and receiver sides. This approach, complementary to the previous ones, prepares the longer-term introduction of 100 Gbit/s systems.
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Spencer Chin is a contributing editor for TMCnet. To see more of his articles, please visit his columnist page.

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