  We study optical Bloch oscillations in the one- and two-dimensional arrays of
helical waveguides with transverse refractive index gradient. Longitudinal
rotation of waveguides may lead to notable variations of the width of the band
of quasi-energies and even its complete collapse for certain radii of the
helix. This drastically affects the amplitude and direction of Bloch
oscillations. Thus, they can be completely arrested for certain helix radii or
their direction can be reversed. If the array of helical waveguides is
truncated and near-surface waveguide is excited, helix radius determines
whether periodic Bloch oscillations persist or replaced by the irregular
near-surface oscillations.
