C2N – DAC-less PAM-4 generation

DAC-less PAM-4 generation in the O-band using a silicon Mach-Zehnder modulator

To cope with the demand of increasing bit rates for a limited bandwidth, 4-level pulse amplitude modulation (PAM-4) is a promising economical solution to replace on-off keying (OOK). We demonstrated PAM-4 signal generation using a silicon Mach-Zehnder modulator (MZM) driven by two independent binary streams. The PAM-4 signal is thus generated directly on the chip, avoiding the use of power-hungry digital-to-analog converters (DACs). In comparison with a commercially available LiNbO3 modulator, the penalty is only 2 dB at the KP4 FEC threshold of 2.2x10^-4.