  Considering the concept of "{\it nonlinear coherent states}", we will study
the interference effects by introducing the {\it "superposition of two classes
of nonlinear coherent states"} which are $\frac{\pi}{2}$ out of phase. The
formalism has then been applied to a few physical systems as "harmonious
states", "SU(1,1) coherent states" and "the center of mass motion of trapped
ion". Finally, the nonclassical properties such as sub-Poissonian statistics,
quadrature squeezing, amplitude-squared squeezing and Wigner distribution
function of the superposed states have been investigated, numerically.
Especially, as we will observe the Wigner functions of the superposed states
take negative values in phase space, while their original components do not.
