200-Gbit/s PAM4 Generation by a Dual-Polarization Mach-Zehnder Modulator Without DAC

Abstract

In this experiment, we generate PAM4 signals based on a dual-polarization Mach-Zehnder modulator (DP-MZM) without DAC. Two high-speed binary OOK signals with different driving voltages are used to modulate a DP-MZM. After modulation, the intensity of the optical OOK signal in a polarization state is 0.7 times of the other. In this way, up to 200-Gbit/s PAM4 signals can be successfully generated. We also measure the BER performance of the generated PAM4 signals after 1-km dispersion shifting fiber (DSF) transmission. Based on the experimental results, the generated 160-Gbit/s PAM4 signal can be successfully transmitted over 1-km DSF, satisfying the hard-decision forward error correction (HD-FEC) threshold of $3.8\times 10 ^{\mathbf {-3}}$ . Moreover, the system can support up to 200-Gbit/s PAM4 signal transmission over 1-km DSF when satisfying the soft-decision forward error correction (SD-FEC) threshold of $2\times 10 ^{\mathbf {-2}}$ .