  Knowing the dispersion regime (normal vs anomalous) is important for both an
isolated waveguide and a waveguide array. We investigate by the Finite Element
Method the dispersion properties of a LiNbO3 waveguides array using two
techniques. The first one assumes the Coupled Mode Theory in a 2-waveguide
system. The other one uses the actual diffraction curve determined in a
7-waveguide system. In both approaches we find that by decreasing the array
period, one passes from normal dispersion by achromatic point to anomalous
array dispersion. We then illustrate the wavelength separation by doing
Runge-Kutta light propagation simulations in waveguide array. As all the
parameters values are technologically feasible, this opens new possibilities
for optical data processing.
