A Double S-Bend Geometry With Lateral Offset for Compact Two Mode Interference Coupler

A double S-bend lateral offset structure has been proposed for the reduction of length and S-bend loss of 2×2 two mode interference (TMI) coupler. The coupling characteristics of the proposed structure are compared with those of conventional TMI structures using a simple mathematical model based on sinusoidal modes. It is seen that the longitudinal beat length for the proposed TMI coupler is reduced by 15% of beat length of a conventional TMI coupler whereas the S-bending loss is reduced by ~ 50% by using lateral offset in the double S-bend structure. The effect of fabrication tolerance on power imbalance for the proposed TMI structure is also compared with other TMI structures. It is seen that the fabrication tolerance for the proposed structure with lateral offset is almost same as that without lateral offset.