A technology that would improve the transmission capacity of wavelength division multiplexing (WDM) systems on standard single-mode fiber may affect the majority of installed fiber networks. Researchers from Pirelli Cables and Systems of Milan, Italy, and AT&T Labs in Red Bank, N.J., have demonstrated WDM transmission over 75 km of single-mode fiber at 40 Gb/s for each of four channels. They also achieved 320-Gb/s transmission over 32 10-Gb/s channels across 375 km. Prior to these experiments, it has been possible to transmit only a single wavelength at 40 Gb/s using fiber gratings.