Basically you could have a high-powered light source with light powered light gates that allow light to multiplex like a repeater, but through multiple channels, to solve the issue of needing to multiplex light. I believe there’s already an example of this in company files. It appears like a diaphragm.
The optical clock is the CPU, which gets pulses of light as they bounce off the racetrack. The pulses are then used to calculate things.