Equalization Enhanced Phase Noise in Coherent Optical Systems with Digital Pre- and Post-Processing

Abstract

We present an extensive study of equalization enhanced phase noise (EEPN) in coherent optical system for all practical electronic dispersion compensation configurations. It is shown that there are only eight practicable all-electronic impairment mitigation configurations. The non-linear and time variant analysis reveals that the existence and the cause of EEPN depend on the digital signal processing (DSP) schemes. There are three schemes that in principle do not cause EEPN. Analysis further reveals the statistical equivalence of the remaining five system configurations resulting in EEPN. In three of them, EEPN is due to phase noise of the transmitting laser, while in the remaining two, EEPN is caused by the local oscillator. We provide a simple look-up table for the system designer to make an informative decision regarding practicable configuration choice and design.

Keywords

• coherent receivers
• quadrature amplitude modulation (QAM)
• equalization-enhanced phase noise (EEPN)
• laser linewidth, optical communication
• digital signal processing (DSP)
• electronic dispersion compensation (EDC)