Maximum likelihood sequence detection receivers for nonlinear optical channels

The space-time whitened matched filter (st-wmf) maximum likelihood sequence detection (mlsd) architecture has been recently proposed (maggio et al.,2014). its objective is reducing implementation complexity in transmissions over nonlinear dispersive channels. the st-wmf-mlsd receiver (i) drastically reduces the number of states of the viterbi decoder (vd) and (ii) offers a smooth trade-off between performance and complexity. in this work the st-wmf-mlsd receiver is investigated in detail. we show that the space compression of the nonlinear channel is an instrumental property of the st-wmf-mlsd which results in a major reduction of the implementation complexity in intensity modulation and direct detection (im/dd) fiber optic systems. moreover,we assess the performance of st-wmf-mlsd in im/dd optical systems with chromatic dispersion (cd) and polarization mode dispersion (pmd). numerical results for a 10 gb/s,700 km,and im/dd fiber-optic link with 50 ps differential group delay (dgd) show that the number of states of the vd in st-wmf-mlsd can be reduced 4 times compared to an oversampled mlsd. finally,we analyze the impact of the imperfect channel estimation on the performance of the st-wmf-mlsd. our results show that the performance degradation caused by channel estimation inaccuracies is low and similar to that achieved by existing mlsd schemes (0.2 db). © 2015 gabriel n. maggio et al.