Design and Simulation of an Integrated Adiabatic Transition for OADM Devices

The increasing diffusion of WDM communication systems requires low cost and efficient optical add-drop devices to add or drop channels at predefined wavelengths with reduced insertion loss and cross-interference. Many fiber based devices have already been proposed, however their integration allows an increase in the compactness and mechanical stability. We designed an integrated OADM that is composed of an asymmetric adiabatic transition followed by an asymmetric grating that converts the supermodes of the combined structure. In this paper we focus our attention mainly on the design of the transition that, besides having low insertion losses, should also be tolerant to the variation of the fabrication parameters and in particular of the grating position. Assuming typical glass on silica waveguides, the transition geometry has been determined using the coupled mode theory. Then the result have been verified and optimized with BPM simulations.