  We introduce Bloch-wave beatings in arrays of multimode periodically bent
waveguides with a transverse refractive index gradient. The new phenomenon
manifests itself in the periodic drastic increase of the amplitude of the Bloch
oscillations that accompanies resonant conversion of modes guided by the
individual waveguides. The Bloch-wave beatings are found to be most pronounced
when the length of the resonant mode conversion substantially exceeds the
longitudinal period of the Bloch oscillations. The beating frequency decreases
when the amplitude of waveguide bending decreases, while the beating amplitude
is restricted by the amplitude of the Bloch oscillations that emerge from the
second allowed band of the Floquet-Bloch lattice spectrum.
