The potential of silicon-based designs for various optoelectronic functions is discussed. Sibased light detectors are the most advanced, especially in the form of metal-Si-metal (MSM) photodetectors. They use Si band to band absorption for visible light and Schottky-barrier emission for the infrared (IR). The different light sources show rapid progress, but still face challenges to reach a quantum efficiency of 10−2. In addition to the intrinsic silicon based designs, some new Si breadboard concepts are shown: especially for waveguides, modulators and all-optical amplifiers, it may be advantageous to add entirely different materials (polymers, glasses, BaTiO3 or Al2O3) onto the Si wafer.