A 50Gb/s optical PAM4 transceiver heterogeneously integrated with microring modulator and avalanche photodiode

This paper presents a CMOS quarter-rate PAM4 transceiver link integrated over wirebonds with a two-segment silicon-based microring resonator (MRM) and an avalanche photodiode (APD). The transmitter (TX) CMOS chip consists of high-swing AC-coupled MSB/LSB drivers implemented using the pulsed-cascode topology. The receiver (RX) CMOS chip consists of a inverter-based analog front-end, comparators and deserializer circuits. Implemented in 28nm CMOS technology, the optical transmitter sends 50 Gb/s PAM4 at a voltage swing of 4.2Vppd and the receiver achieves an optical modulation amplitude (OMA) sensitivity of -4.66 dBm at 50 Gb/s PAM4 data-rate.