Enhanced frequency-domain fractionally spaced equalization for coherent optical transmission system with colored noise

Abstract

An enhanced minimum mean-square-error (MMSE) frequency-domain (FD) fractionally spaced equalizer (FSE) for polarization demultiplexing is proposed in the presence of colored noise. The 2-norm of the estimated channel matrix and polynomial fitting of equalization coefficients are introduced to mitigate the colored noise without requiring knowledge of the optical and electrical filtering. Simulation results show that ∼3-dB improvement of equalization performance is achieved compared to conventional MMSE FD-FSE in an 8 × 112-Gbit∕s wavelength-division multiplexing polarization-division multiplexing-quadrature phase shift keying transmission system over a 1200-km single mode fiber link.

Stokes Space Modulation Format Identification for Optical Signals Using Probabilistic Neural Network

“…Among these methods, Stokes space based methods have attracted significant attentions because they are insensitive to carrier phase noise, frequency offset and polarization mixing. Furthermore, Stokes space based methods can be applied before modulation format dependent algorithms including polarization demultiplexing [18], frequency offset compensation as well as carrier phase recovery, and could ensure optimal system performance.…”