system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't computers use glassfiber cables in stead of the old electric cables?

We all know that glassfiber transports data way quicker than the electric cables. Computer need to transport a lot of information from one component to the other. Why do computers still use the old electric cables in stead of glassfiber cables? Or is the transport of data from one component to the other not the bottleneck?
gpt
Okay, point of order: the data transfer speed is the same.  Both electric signal and light travel at c.

The difference is that large-scale fiberoptical connections allow much greater bandwidth and loose less power over distribution, so the possible length of an FO cable is significantly larger than copper wires.  In a computer, both of these can be overcome quite easily by running more tiny wires, and the fact that a desktop/laptop computer is generally no more than 18" from point to point.

There's also the problem that processing components, e.g. ALU, CPU, GPU, memory, cannot function with light - just electric charge.  So to use "glassfiber", as you put it, inside a computer, you'd have to transform every signal from electrical to light and back at every single stage, requiring even more electronics - this bottlenecks the system and severely increases power draw, complexity, and necessary components.

This is why you see Fiber Optics *between* nodes of a high-performance cluster - they need to perform *as* a single computer and it's easier to run one fiber line than eight ethernet lines, both from a networking and implementation standpoint, and they run a reasonably long distance.  There are competing copper standards, e.g. InfiniBand, that carries similar bandwidth and speed to fiber in the context of server/performance clusters, but are less useful for international or transcontinental lines due to cost and signal loss.

Edit: Also, the copper-fiber difference disappears even further, as internal communications of a computer don't occur over any sort of standard (ethernet, infiniband, token-ring, whatever) - they carry straight charge point to point, very similar to dark fiber.  When you take out the processing time for the standard, there's even less speedup.