The reason fiberoptic is better than a mirrored duct for data transfer is because you can pack say 32 or 64 fibers into a cable, that means 32 or 64 points of light that are either "on" or "off", creating a 32-bit or 64-bit word size and enabling data transfer. You can't do that with ducts.

Fiber obtic cables, again, are just transferring light. They don't have an on or off state. It's just light.

There is an on and an off state. Either the light is on or the light is off. That's how it translates into binary. Literally that's what binary data is: a single data-point is either on or off. Put a bunch of them together to create words with 2^n^ possible combinations per word where n is the number of datapoints. For electrical data, that's the voltage level of one wire or bus lead. For fiberoptics, it's each individual fiber. It's either on or off, that's the whole point.

You'd have to make sure the mirrors are angled correctly, and it'd only work if the light is collumated, so it's all traveling parallel and not spreading out.

[...]

You don't need perfectly aligned mirrors that would decay in effectiveness with dust

The mirrors don't have to be angled precisely. If you take a cylindrical tube, and make the inside a mirrored surface, then all light traveling down it will continue traveling downward as it bounces. The only time the angle matters is around turns, but that's easy enough to angle correctly.

It also doesn't need to be columnated, but the thing about the fish-eye dome is that with a flat lense on bottom, it does output columnated light from the wide-angled light it receives. That's how convex defraction works.

And dust wouldn't be an issue if your tubes are sealed.

Fiberoptics would technically work, but it's more material than you need because it would require running fiberoptic cables everywhere instead of just using hollow chromed tubes. Also, the quantity of light it can receive and transmit is limited to the thickness of the cable.

Fiberoptics are great for high-speed data transfer because of data-integrity and the fine-pointed nature of the fibers. But they aren't ideal for moving large amounts of light where precision isn't needed, e.g. enough natural daylight to brighten several rooms.