Optimum design and performance evaluation of an all-fiber add-drop multiplexer based on a grating coupler

The optimum design and performance evaluation of an add-drop multiplexer (ADM) based on a grating coupler is presented. The equations describing its behavior are numerically solved and surface plots where the relevant ADM transfer functions are plotted against two physical parameters of importance are introduced as an useful tool to evaluate the tradeoffs involved in the optimum design of the structure. The merits of the ADM designed using the above criteria are evaluated under realistic operation conditions by means of computer simulation using laser rate equations, pseudorandom modulation sequences, and eye closure measurements to estimate the crosstalk penalty in both the drop and add operations. It is found that, whereas a Blackman apodization gives optimum results in terms of crosstalk only when the drop operation is considered, a Hamming apodization yields an overall superior performance when both add and drop functions are considered.