A 56Gb/s PAM4 Optical Receiver Integrated with Si-Ge APD

This paper presents a broadband optical PAM4 receiver (RX) integrated with a Si-Ge avalanche photodiode (APD) by wire bonding. Fabricated in 28nm CMOS, the 56Gb/s PAM4 receiver achieves an optical modulation amplitude (OMA) of -7dBm at BER of 10 ^-4 and power efficiency of 1.61pJ/bit.