We demonstrate 10-Gb/s/ch operations of high-density, low-cost 12-channel optical modules for optical interconnections. These optical modules that we developed are designed to be pluggable into cards with an electrical connector. These pluggable modules will enable cards to be manufactured much more easily since they allow the manufacturing processes of optical modules and cards to be separated. An electrical connector with a clamp spring is used to connect a ceramic substrate with a printed circuit board (PCB). An anisotropic conductive film (ACF) is used to transmit electrical signals between the ceramic substrate and the PCB. To achieve optical coupling, optical fibers are butt-coupled with optical devices mounted in a cavity on the ceramic substrate. Alignment between the twelve optical fibers and the 12-channel optical device is achieved using guide pins fabricated in the ceramic substrate and guide holes fabricated in the optical connector.