An accurate analysis for two-mode interferometer based Mach-Zehnder interferometers interleaver

By using a more accurate analysis, we investigate the effect of the mode coupling and radiation loss of a two-mode interferometer (TMI) which is employed in the design of Mach-Zehnder interferometer interleaver by considering different branching angles and index contrasts. Based on our study, we find that the transmission characteristics of a TMI in the interleaver design cannot always be treated as a simple zero gap directional coupler (DC), called pure model. Under certain conditions, its characteristics should be treated as a zero gap DC combined with two variable gap DCs. and correspondently called integrated model. The conditions under which a TMI is treated as pure model or integrated model are defined in terms of branching angle and index contrast. Our findings are confirmed with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.