  The variance of nonlinear phase noise is analyzed by including the effect of
intrachannel cross-phase modulation (IXPM)-induced nonlinear phase noise.
Consistent with Ho and Wang [1] but in contrary to the conclusion of both Kumar
[2] and Green et al. [3], the variance of nonlinear phase noise does not
decrease much with the increase of chromatic dispersion. The results are
consistent with a careful reexamination of both Kumar [2] and Green et al. [3].
