Background conversion of light waves in distributed structures

An analysis is made of the process of wave conversion outside the region of the strongest resonant coupling. It is shown that the efficiency of wave conversion in the case of a considerable off-resonance detuning can be quite high and it should be taken into account. Background conversion of waves can be responsible for low values of the maximum decoupling of waves in devices utilizing distributed structures. An analysis is made of the use of background conversion in determination of the maximum efficiency of coupling of waves in a given distributed structure.