Channel interference study and power ratio optimization on two optical Nyquist-PM-QPSK signals with spectral overlap

Opt Express. 2019 Nov 25;27(24):35574-35587. doi: 10.1364/OE.27.035574.

Abstract

Recent signal processing of optical signals has involved possible overlapping of the spectra from the adjacent optical channels for channel multiplexing and improving system throughput. However, the incurred channel interference performance has not yet been carefully characterized. In this paper, we carry out simulations and experiments to investigate various system parameters that determine such adjacent channel interference performance and further optimize the channel power ratio when two optical channels, each carrying a Nyquist shaped and polarization multiplexed quadrature phase-shift keying (Nyquist-PM-QPSK) signal, are being multiplexed with optical spectral overlap. With a properly designed successive interference cancellation (SIC) algorithm, both channels can be successfully separated and decoded individually. The OSNR penalties due to possible time offset, polarization rotation, and frequency offset between the two adjacent optical channels are investigated. The power ratio between the two adjacent optical channels are further optimized with respect to the OSNR penalties.