Integrated electrooptic multielectrode tunable filter

We introduce a novel electrooptic integrated tunable filter for multiwavelength communication networks. The proposed device consists of an asymmetric co-directional coupler with multiple electrodes for attaining an alternating /spl Delta//spl beta/ effect. The proposed structure can function as a multiplexer-demultiplexer and as a narrow bandwidth tunable filter, with conversion efficiency 1 within the entire tuning range. The amount of asymmetry in the waveguides can be achieved by combining a wide waveguide with low /spl Delta/n fabricated by Ti:LiNbO/sub 3/ process with a second narrower waveguide with high /spl Delta/n using proton exchange procedure. This combined technology would assure very narrow bandwidth in the 1 nm range. The demand of conversion efficiency 1 all over the tuning range is essential to several network architectures. We give the formulation for an asymmetric directional coupler with alternating /spl Delta//spl beta/, and show that the need for many electrodes is a must in order to reject the satellite passbands out from the tuning range. We give a simple expression for estimating the number of electrodes needed. Additionally, we give some suggestions in order to reduce the voltage applied to the electrodes for tuning.>