a kind of 50 Gbit/s PAM4 QSFP28 optical transceiver module is proposed
which can meet the demands of 40 km transmission. The PAM4 technology is used to increase the transmission capacity in each single wavelength. At the receiver side
the key component of the photo-detector is APD
which can increase the ability of identifying weak signal
and meet the requirement of 40 km transmission in 50 GE. The circuit of reception unit is optimized to obtain a better transmission effect. The result indicates that the transceiver can work steadily