In this paper, we propose an iterative block equalizer for long-haul Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) communication systems. The proposed scheme is based on a soft Minimum Mean-Squared Error (MMSE) iterative block equalizer. Two different channel estimation methods are also discussed. The performance and computational complexity of the proposed iterative equalization and channel estimation techniques are evaluated as well. The obtained Bit Error Rate (BER) performance reveal that the iterative equalizer outperforms the linear equalizers by almost two orders of magnitude.