We present the first all-silicon integrated optocoupler, whose fabrication, using ion implantation into SiO2, is completely compatible with standard Si technology. It is based on Ge-implanted SiO2 layers as light emitter exhibiting bright blue-violet electroluminescence light with a record wall-plug efficiency of 0.5%. The electroluminescence is explained with a model in which electrons enter the SiO2 layer via tunnel injection and excite the luminescence centers by impact excitation or field ionization. A radiative T-1-S-0 transition of these luminescence centers then causes the observed electroluminescence. Finally, we show that these optocoupling devices hold great promise for integrated optoelectronic applications, especially in the field of sensor and biotechnology.