Inter-channel nonlinear interactions between adjacent channels in wavelength-division multiplexed systems are considered the predominant factor in limiting the communication rate of the fiber-optic channel. The most pronounced nonlinear effect was recently shown to manifest itself as phase noise. Interestingly, the phase rotation exhibits very long temporal correlations and depends crucially on the transmission power and modulation format. We examine information-theoretic properties of the resulting channel and further derive bounds on its capacity.