The apparatus includes a case having a base member, two partial side members, and a lid member to provide a spatial volume with an opening at a back end of the base member. Additionally, the apparatus includes a PCB installed inside the spatial volume over the base member with a pluggable connector at the back end. The apparatus includes one or more optical transmitting devices in transmit-optical-sub-assembly package, each being mounted upside-down on the PCB and including a built-in TEC module in contact with the lid member and a laser output port aiming toward the back end. Furthermore, the apparatus includes a silicon photonics chip including a fiber-to-silicon attachment module, mounted on the PCB and coupled to a modulation driver module and a trans-impedance-amplifier module. Moreover, the apparatus includes an optical input port and output port being back connected to the fiber-to-silicon attachment module.