Fiber Nonlinearity Impact on Direct-Detection Block-Wise Phase Switched Systems

We carry out comprehensive analysis on the fiber nonlinearity impact on the block-wise phase switching (BPS) direct detection (DD) systems. We find that the degenerate four-wave mixing components produced by the interaction between the main carrier and the subcarriers are intrinsically compensated through the direct detection process. For a 100-Gb/s BPS-DD system over 80-km standard single-mode-fiber link, the optimum launch power is found to be 5 dBm, and the optimum carrier-to-signal power ratio is 12 dB. For a single-channel BPS-DD system, the fiber nonlinearity impairment is reduced when low-dispersion fiber is used. However, for a multi-channel BPS-DD system, the nonlinearity noise induced by the crosstalk among the channels is enhanced when the chromatic dispersion of the fiber link decreases.