PITTSBURGH, March 27 -- Marconi and Telecom Italia announced they have transmitted dense wave division multiplexing (DWDM) over dispersion-shifted fiber, quadrupling the number of wavelengths an optical fiber can support. This is a technical breakthrough in the optical transmission field, Marconi said. The technology, introduced three months ago on Telecom Italia's backbone link between Florence and Rome, will enable traffic transmission techniques over existing DSF fiber infrastructures and will allow users to maximize their existing fiber investments, according to Marconi. "Network providers can look again at their legacy fiber installed in the ground and reconsider its inherent value," said Lorenzo Costagli, vice president of development for Marconi. "Operators can now deploy advanced DWDM photonics technology over fiber that has been installed for up to 15 years -- fiber that was previously considered unsuitable for high-capacity transmission."