Analog Signal Processing Circuits for a 400Gb/s 16QAM Optical Coherent Receiver

A novel structure of analog signal processing circuits for coherent receivers is proposed and implemented in 28-nm CMOS technology with 1V supply voltage in this work. To avoid excessive taps in equalizer or prolix circuit modules, the system combines the crosstalk equalizer and carrier phase recovery circuits with the application of 2 kinds of multipliers to compensate linearity for higher accuracy. In order to achieve stronger converging ability, simplify the system realization and further reduce power dissipation, the chromatic dispersion equalizer uses DFE instead of FFE to eliminate post cursor. Simulation results show circuits are capable of equalizing signals of 40-ps/nm chromatic dispersion effect, 300-kHz dynamic polarization crosstalk and 100MHz frequency offset with power of 1.2 Watt.