Rib structures in card to backplane optical high speed interconnect couplers and related sensitivity for computer motherboards

Abstract

The single-mode/multi-mode rib structures for high-speed optical card-to-backplane interconnects in computer motherboards are presented. In the system, we used evanescent coupling with the required known coupled power for the horizontal waveguide coupler and almost full power coupling in the vertical waveguide coupler. The rib structure parameters are varied to obtain single mode or multimode waveguides, where the rib width/height ratio and the slab height effectively control the single mode or multimode structures. For the required coupled power, the single-mode rib-waveguides require lower values of coupling length compared to that of the multimode rib- waveguides. The larger core area of SM rib structure to couple power easily from the source to the waveguide is shown. The modal dispersion effect arising in multimode waveguides is studied to improve the bit rate performance. The fabrication to prepare the polymeric optical waveguide with the conventional process by patterning with mask is shown. The experimental repeated results show that the output power variation limits within 10%. The simulated BeamPROP results for the light coupling are compared with the theoretical and experimental results.