RZ versus NRZ modulation format for dispersion compensated SMF-based 10-Gb/s transmission with more than 100-km amplifier spacing

We compared numerically and experimentally the transmission behavior of return-to-zero (RZ) and nonreturn-to-zero (NRZ) modulated signals, 10 Gb/s were transmitted over 2040-km standard single-mode fiber using an alternating dispersion compensation scheme in a recirculating loop with 102 km amplifier spacing. Receiver sensitivities of -33 dBm (NRZ) and -35 dBm (RZ) could be achieved. RZ allows for a simple linear dispersion compensation whereas NRZ suffers from nonlinear signal distortion. NRZ requires under-compensation of the linear chromatic dispersion dependent on signal power and transmission length. Therefore, NRZ makes network design more difficult.