Directly modulated 2.5 Gb/s x 16-channel WDM transmission over 640 km of single-mode fiber using dispersion compensating fiber

We demonstrate a directly modulated 2.5 Gb/s/spl times/16 channel wavelength-division-multiplexed (WDM) transmission system over 640 km of conventional single-mode fiber using the dispersion compensating fiber. The capacity of this system could be increased easily without adjusting the outside plant by replacing the directly modulated 2.5-Gb/s channels with the externally modulated 10-Gb/s channels. To demonstrate the feasibility of this capacity upgrade, we implement a 130-Gb/s (10 Gb/s/spl times/12 channels+2.5 Gh/s/spl times/4 channels) WDM transmission system using the same fiber-optic link.