We propose an on-board integrated optics (OBO) scheme within a 50G/10G combo passive optical network (PON) system, for the first time to our best knowledge, which can achieve high port density, low cost, and low power consumption required by the 50G PON system. We provide an OBO scheme that integrates record-high power distributed feedback (DFB) lasers, low insertion loss silicon modulators, a planar lightwave circuit wavelength-division multiplexer, and avalanche photodiodes on a single board, which can solve key issues faced by the demand of coexistence and smooth evolution from 10G to 50G PON for global access network operators. In this system, the slope efficiency of the lasers has been optimized at high temperatures, allowing the output power of the lasers to achieve a record-breaking 23.5 dBm at 1577 and 1342 nm, while reducing cooling power consumption to realize low carbon emission in access networks. We developed a low-loss broadband silicon modulator to meet the large power budget and high data rate requirements of 50G PON by optimizing doping parameters and constructing electrodes that match the driver. This silicon modulator has a 6.6 dB insertion loss and an electro-optic bandwidth of more than 38 GHz, making it the ideal silicon modulator for 50G PON systems. In addition, we verify the end-to-end performance, including receiver sensitivity in the upstream direction and the dispersion penalty in the downstream direction. This suggests that the OBO scheme can satisfy the criteria of the 50G PON system according to the ITU-T G.9804 standard series.