Anharmonic Bloch oscillations in a coupler composed of two parallel optical fibre arrays

The effects of laser beam propagation in a coupler composed of two parallel optical-fibre arrays are studied by the coupled-mode method taking into account the interaction of a given fibre with the nearest neighbours and the linear dependence of the propagation constant on the fibre number. It is shown that, due to the complex structure of each subsystem, the structure of light intensity spatial distribution becomes significantly complicated in the system under study. The occurrence of space limited transverse light diffraction is predicted.