A three dimensional optical interconnect device having one input and multiple output ports mounted on the same surface of a SOI wafer is disclosed. The first Si surface has a silicon waveguide with a straight portion, a first and a second 45 degree end reflectors and multiple optical splitters arranged in a sequence along the straight portion. The second silicon surface has an insulating layer and an active optical input device (VCSEL laser) and multiple receiver ports mounted on the insulating layer. The first end reflector is aligned to the input optical device, the optical splitters and the second end reflector are sequentially aligned to the photodetectors respectively. Multiple optical paths are formed from the input optical device to each of photodetectors by a reflection from each aligned optical splitter and a reflection from the second end reflector through the silicon substrate.