Organic optical multi-chip modules for high bandwidth-density and low-power link in high-performance computing systems are developed. The light from polymer optical waveguide is coupled to a multimode fiber through a total internal reflection (TIR) mirror and a newly-developed compact fiber connector with lens arrays. For preventing a UV adhesive for connector assembly or an underfill resin for optoelectronic chip assembly goes into the TIR mirror cavity, the materials with proper viscosity and wettability are tested. As a result, 35 Gb/s operation is achieved for both transmitters and receivers after the connector assembly. The link budget analysis is also done. We report on the detail of the link budget analysis and the assembly optimization.