Comparison of Transmission Performance of 40-Gb/s Optical Duobinary and DCS-RZ Signals Using 10- and 40-Gb/s $\hbox{LiNbO}_{3}$ Mach–Zehnder Modulators

We investigated a cost-effective method using 10-Gb/s $\hbox{LiNbO}_{3}$ Mach–Zehnder Modulators (MZMs) for transmitting 40-Gb/s duobinary nonreturn-to-zero (NRZ) and duobinary carrier-suppressed return-to-zero (DCS-RZ) signals. The transmission performance of the signals was investigated. The optimum bandwidths of low-pass filters in transmitters using 10- and 40-Gb/s $\hbox{LiNbO}_{3}$ MZMs were also investigated. The calculated transmission performance of the transmitter using 10-Gb/s $\hbox{LiNbO}_{3}$ MZMs was compared to that using 40-Gb/s $\hbox{LiNbO}_{3}$ MZMs. The effect of the bias offset in the transmitters was investigated. Compared to duobinary-NRZ and DCS-RZ signals generated by a transmitter using 40-Gb/s $\hbox{LiNbO}_{3}$ MZMs, those generated by using 10-Gb/s $\hbox{LiNbO}_{3}$ MZMs can be transmitted with 1-dB power penalty over 480-km transmission.