An iterative equalization scheme for suppressing intrachannel nonlinearities in high-speed optical transmission systems operating at 40 Gb/s is presented. The proposed method employs a noise-predictive filter to mitigate the colored noise due to amplified spontaneous emission noise and optical filtering. The maximum a posteriori probability symbol detection implemented as the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm is employed to suppress the intrachannel nonlinear effects. Soft decision outputs provided by the noise-predictive BCJR equalizer are processed by an iterative low-density parity-check decoder