Transmission of 2.5-Gb/s WDM channels spaced at 5 GHz over 480 km of single-mode fiber

We have demonstrated the transmission of six 2.5-Gb/s wavelength-division-multiplexed (WDM) signals spaced at 5 GHz over 480 km of single-mode fiber. In this experiment, the WDM signals were demultiplexed by using a simple optical filter despite their extremely narrow channel spacing. The optical bandwidth of this filter was optimized by considering both the interchannel crosstalk and intersymbol interference. The results indicate that it should be possible to transmit more than 1000 2.5-Gb/s channels spaced at 5 GHz.