You can get that with one fiber-optics cable. In principle they just need to bond a led on both ends of a fiber optical strand and put a signal converter chip on both ends of the cable to make it compatible with electrical ports. Eventually it could become cheap enough to stuff chips into cables, especial if the led and signal converter are integrate into one tiny piece of silicon, and you do something clever with the fact that microchip circuits are affected by light.
20 Gbps isn't even a problem with copper. regular RG-58 coax has about 30 GHz of bandwidth. it's just more expensive than twisted pair
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