40-Gb/s transmission over multiple 120-km spans of conventional single-mode fiber using highly dispersed pulses

We demonstrate the transmission of a 40-Gb/s signal over multiple (up to six) 120-km spans of conventional single-mode fiber (SMF). We use a very low duty cycle return-to-zero (RZ) format which employs optical pulses much shorter than the bit-period. The resulting broad spectrum of these short pulses reduces nonlinear effects and enables the transmission of the signal over long distances.