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

We demonstrate 20-Gb/s 4-level pulse amplitude modulation (PAM-4) signal generation using a silicon Mach-Zehnder modulator (MZM) in the O-band. The modulator is driven by two independent binary streams. and the PAM-4 signal is thus generated directly on the chip, avoiding the use of power-hungry digital-to-analog converters (DACs). With optimized amplitude levels of the binary signals applied to the two arms of the MZM, a pre-forward error correction (FEC) bit-error rate (BER) as low as 7.6 x 10(-7) is obtained. In comparison with a commercially available LiNbO3 modulator, the penalty is only 2 dB at the KP4 FEC threshold of 2.2 x 10(-4). (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement