Study of cross coupling in transition bends using cascaded coupler segment method

An analysis to find out the cross coupling of transition bend regions in integrated optic directional coupler (IODC) has been carried out using a novel method, namely the cascaded coupler segment method. A study has been conducted to see cross couplings in three types of S-bends, sine, cosine and double arc. It is seen that cosine S-bend offers the lowest cross coupling. Effect of variation in transition lengths on cross coupling is studied. It is then observed that as the transition length increases the cross coupled power also increases. Expression for equivalent interaction length in terms of transition length is derived. The results can be used to arrive at an optimum transition length and type of S-bend.<>