Reduction of an S-bend structure size for optic telecommunication

The S- Bend structures are used to connect different parts of a circuit such as optical couplers, modulators and switches. These devices must be designed to minimize the signal loss caused by the radius of the curvature and several alternatives have been proposed to reduce these losses. However, minimizing these losses requires a high value of the curvature radius which leads to a structure length incompatible with the integrated optics. In this paper a new approach to connect the S-Bend and the straight waveguide in order to minimize losses is presented. Performance evaluations of the S-Bend, with and without the proposed optimization, are carried on with the Rsoft Beamprob commercial software package. Simulations result allowed a distinction between the radiation losses and the transition losses. They also confirm that the radius of curvature has a great influence on the losses which increase when the radius decreases. By introducing an optimum offset at the different transitions, it was possible to minimize the length of the structure for the integrated optics and this for a relative minimum of losses.