  We investigate the optical beam behavior in the periodical array of the
coupled optical waveguides with the monotonic change of the refractive index in
the transverse direction. We consider the dependence of the form of the optical
beam on the boundary conditions. It is well known that if the input wave packet
is wide enough, the optical Bloch oscillations occur, while for the enough
narrow input wave packet the breathing mode is observed. We show that if the
input wave packet is neither too wide nor too narrow, the optical beam takes a
peculiar form which can be considered neither as the Bloch oscillations nor as
the breathing mode. We qualitatively explain the transformation of this
intermediate form of the optical beam when the width of the input wave packet
changes.
