Analysis and Experimental Study of a Silicon Photonic Single MRM-Assisted MZI PAM-4 Modulator

We report on the analysis and experimental study of a silicon photonic single microring modulator (MRM) assisted Mach-Zehnder interferometer for high-speed four-level pulse amplitude modulation (PAM-4). The static extinction ratio (ER) of the proposed device is 18 dB larger than that of a single MRM with the same design parameters. Under 0 V reverse bias voltage, the measured 3-dB electro-optic bandwidth of the device is 20 GHz. Based on the enhancement of the ER, the measured 40 Gb/s on-off keying eye diagram of the device shows larger modulation amplitude than that of the single MRM. We further present 76 Gb/s PAM-4 using the proposed device in a back-to-back configuration, with the measured bit error rate below the hard-decision forward error correction threshold of 3.8 × 10
^-3
.