Application of the coupled mode theory to the problem of coupling between bent and straight waveguides.

The coupling between high finesse (up to 140) cylindrical microresonators and straight waveguides is analysed using the Coupled Mode Theory and numerically calculated 2D fields of the unperturbed bend and straight waveguides. The calculated coupling constants are in good agreement with bouth experiments and other numerical methods. Extension of our approach to more advanced geometries, like coupling between bends, is straightforward.