Maximum Likelihood Sequence Detection Receivers for Nonlinear Optical Channels

Abstract

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).

Design of MLSD-based receivers for short-range optical communications using the Volterra expansion

“…3, it is important to correctly choose M to decrease the modeling mismatch. In addition, it is possible to also choose the number of branches considered in the filter bank in order to decrease the receiver complexity, by truncating the system models represented by (8) and (9). In the rest of the paper, we denominate the total number of branches considered in the receiver as U .…”

“…Recently, [8], [9] used the Volterra-series Expansion theory [10] to design a reduced-complexity MLSD receiver for optical channels, the Space-Time Whitened Matched Filter MLSD (ST-WMF-MLSD). The proposed receiver structure leverages the energy compression provided by an Orthogonal Volterra Kernel model to decrease the memory required by the VD PSfrag replacements A | | 2 Figure 1.…”