It will be shown in this paper, that the mode conversion factor (MCF) as defined for Y-junctions, can be profitably the three lowest-order modes of a channel waveguide. Accordingly, these so-called mode-splitting Q-junctions were designed for implementation in PECVD SiON-technology. Propagation calculations point to crosstalk levels well below-20 dB at 10-20 mm junction length. The produced q-junctions show crosstalk Of at a desired crosstalk level. We have realized several modesplitting junctions in SiON-technology using this strategy. butions over the branches, intensity profiles in the multimodal branch and the beat-pattern of light scattered out of that branch. The characterizations show that a @-junction with a intermodal crosstalk of less than-17 dB has been realized. TO the best applied for the design of three branch junctions for These junctions were characterized by analyzing power distri-I. INTRODUCTION 11. DEVICE PRINCIPLES ULTIBRANCH junctions like the well-known Yjunction (1 + 2) or the less-known Q-junction (1 The mode-splitting behavior of multibranch junctions [2]