Impact of EEPN in Phase-Sensitively Pre-Amplified Fiber-Optic Transmission with Digital Idler Generation and Pre-CD Compensation

This study investigates the effect of equalization-enhanced phase noise (EEPN) on fiber-optic transmission systems that employ a phase-sensitive amplifier (PSA) based on double-sideband (DSB) modulation. The DSB-PSA scheme enables digital chromatic dispersion (CD) pre-compensation, facilitating the universal deployment of phase-sensitive preamplification; however, this process introduces EEPN. Through spectral analysis and visualization, we show that EEPN can be mitigated by phase-sensitive amplification and manifests as frequency-dependent coherent gain fluctuations. Numerical simulations with a 96-Gbaud 16QAM signal confirmed that the PSA significantly improves signal quality, even under severe EEPN conditions with large laser linewidths and/or high CD values.