EEPN mitigation by local oscillator phase isolation with dual pilot carriers

Digital coherent systems can compensate for chromatic dispersion (CD) and estimate phase fluctuations by digital signal processing within receivers. However, such systems suffer from equalization-enhanced phase noise (EEPN) which is the interaction between post-compensation for CD and phase noise of the local oscillator (LO). To address this, LO phase noise must be removed before CD compensation. Typical coherent receivers, however, cannot isolate the LO phase from the transmitter phase, leading to inevitable EEPN and limited transmission distance. In this paper, we propose a novel method to mitigate EEPN with dual pilot carriers multiplexed into a signal. With the pilot carriers, we can isolate the LO phase and eliminate the phase fluctuations of the LO laser prior to CD compensation. This process inhibits the occurrence of EEPN. Numerical simulations confirm that the performance penalty due to EEPN is substantially reduced in beyond 100 Gbaud systems.