Maximum likelihood sequence detection in laser phase noise-impaired coherent optical systems

A maximum likelihood sequence detection (MLSD) receiver is used to detect data sequences in single-carrier coherent optical systems in the presence of laser phase noise. It requires no explicit phase estimation and involves only linear operations. It consistently shows improvement in the OSNR penalty (e.g., 1.1 dB at BER = 10 -4 with memory length L =3) and the laser linewidth tolerance (e.g., around 4 times that of DAML at 1dB OSNR penalty at BER = 10 -4 with memory length L =3) over the wellknown DAML and Mth power approaches in laser phase noise (LPN)- impaired coherent optical systems.