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12 April 2011
Verizon and NEC Corporation of America have demonstrated simultaneous transmission of 100Gbps, 450Gbps and 1Tbps optical signals over an installed fibre network.  The results of the trial, which was performed last year on 3,560 kilometres (2,212 miles) of fibre of Verizon's network in the Dallas area, were outlined in a post-deadline paper at the recent OFC/NFOEC Conference in Los Angeles.
The title of the paper was “Field Experiment with Mixed Line-Rate Transmission (112-Gb/s, 450-Gb/s, and 1.15 Tb/s) over 3,560 km of Installed Fiber Using Filterless Coherent Receiver and EDFAs Only”.  All wavelengths were encoded using dual-polarisation quadrature phase-shift keying (DP-QPSK) with coherent detection – now the standard modulation format for 100 Gbps transmission.  To get to the higher bit rates, beyond 100Gbps, the researchers also used orthogonal frequency division multiplexing (OFDM) to encode each optical wavelength with multiple frequency sub-channels – a technique borrowed from wireless systems, but being actively explored by a number of optical companies for higher-bit-rate transmission.
Since previous Tbps experiments had only been performed in the lab, the researchers focused on achieving long-distance transmission over existing networks.  "As we look to a future when data rates go beyond 100G, it's important to begin examining how these technologies perform," said Glenn Wellbrock, director of optical transport network architecture and design at Verizon, and an author of the paper. "This trial gives us a good first step toward analyzing the capabilities of future technologies."
The paper's revelations come soon after Verizon's recent announcement that will upgrade networks from Chicago to New York, Sacramento to Los Angeles and Minneapolis to Kansas City with 100Gbps transmission technology.
By Pauline Rigby