Fiber nonlinearity precompensation for long-haul links using direct-detection optical OFDM

The use of nonlinearity precompensation in direct-detection optical orthogonal frequency division multiplexed links is investigated by simulation. Because of the presence of a strong optical carrier its performance is poorer than for coherent systems: with compensation the signal quality is found to vary almost periodically across the signal band. We propose and explain the operation of two optical, one electrical and one computational method of removing this periodic variation. Optical filtering of one sideband at the receiver is most effective, but a substantial improvement can be obtained by a simple modification to the precompensation algorithm. (c) 2008 Optical Society of America.