Study of Chromatic Dispersion Impacts on Kramers-Kronig and SSBI Iterative Cancellation Receiver

摘要： Field recovery of single sideband (SSB) signals with direct detection has recently been investigated for short-reach communications. One of the cruxes of such direct-detected transmission system is signal-signal beat interference (SSBI) mitigation without sacrificing spectral efficiency. Among various digital signal processing schemes, Kramers-Kronig (KK) algorithm has attracted considerable interest recently due to its effective mitigation of SSBI, and the phase of signals can be recovered using intensity information. As such, chromatic dispersion (CD) can be digitally compensated. Beside KK algorithm, SSBI can also be sufficiently mitigated iteratively. In this paper, we carry out an 80-Gb/s 160-km transmission experiment to investigate chromatic dispersion impacts on both KK and SSBI iterative cancellation (IC) receiver. It is shown that for KK receiver, optimal carrier-to-signal power ratio (CSPR) values increase with transmission distance. This is because that CD induced peak-to-average power ratio (PAPR) increase violates minimum phase condition, and thus the field cannot be reconstructed accurately, leading to degradation of transmission performance. Consequently, OSNR sensitivity for KK receiver is dependent on CD. In contrast, IC receiver has no limitation of minimum phase condition, and thus exhibits high robustness against CD regardless of CSPRs. Besides, experimental results show that after 160-km transmission at the BER threshold of 10-3, the required OSNR for IC receiver is 1.9 dB lower than that of KK receiver.