In this paper we propose to replace all data and control pads generally present in conventional chips with a new type of ultra-compact, low-power optical interconnect implemented almost entirely in CMOS. The proposed scheme enables optical through-chip buses that could service hundreds of thinned stacked dies. High throughputs and communication density could be achieved even in tight power budgets. The core of the optical interconnect is a single-photon avalanche diode operating in pulse position modulation. We demonstrate how throughputs of several gigabits per second may be achieved. We also show a systematic analysis of the system and preliminary results to support its suitability in emerging DSM technologies.