Silicon photonics enables optical interconnects with high bandwidth, long reach, low power consumption and scalability to very large systems with low-cost. We show that this is also possible with low-loss micron-scale silicon waveguides. We also present results from interposer chip fabricated on 12 µm SOI that enables simultaneous low loss coupling between SM fibres, micron-scale SOI chips, VCSELs, and detectors. Passive optical circuits within the interposer for wavelength multiplexing and power coupling reduce the need for external optical circuits. The interposer acts as a mechanical submount for the optoelectronics and the drivers, which results in a compact subassembly that can be easily integrated into optical modules.