Performance Analysis of Kramers–Kronig Receiver in the Presence of IQ Imbalance

We investigate the impact of IQ imbalance of the transmitter on the performance of the direct-detection system utilizing the Kramers-Kronig receiver. We show through theoretical analysis that the amplitude imbalance, timing misalignment, and IQ phase mismatch create double-sideband distortions, which, in turn, serve to violate the minimum phase condition and also lead to the dispersion-induced RF power fading after transmission. The theoretical analysis is verified by using numerical simulations. The results show that the amplitude imbalance and timing misalignment should be less than 2 dB and 2 ps, respectively, when the receiver sensitivity penalty is smaller than 1 dB for the transmission of a 112-Gb/s 16-QAM OFDM signal.