Even in just the last 20 years we've gone from copper phone lines to cable to fiber.
Is there any reason to suspect that today's fiber (albeit possibly "lit" by tomorrow's fiber modems) will be insufficient twenty years from now? Are we approaching some sort of theoretical limit to the number of beams of light that one glass fiber can transmit?
> Is there any reason to suspect that today's fiber (albeit possibly "lit" by tomorrow's fiber modems) will be insufficient twenty years from now? Are we approaching some sort of theoretical limit to the number of beams of light that one glass fiber can transmit?
No. And the premise that we've gone from twisted pair to coax to fiber in a period of 20 years is similarly silly. Telephone wire is essentially telegraph wire and has been in use since before the American civil war. Coax is from the same century and had been in use for cable TV before the internet was even a thing. Even modern fiber optic cable is older than, say, TCP/IP. The only reason fiber wasn't used to begin with is that the other cable was already in the ground before the internet existed.
Is there any reason to suspect that today's fiber (albeit possibly "lit" by tomorrow's fiber modems) will be insufficient twenty years from now? Are we approaching some sort of theoretical limit to the number of beams of light that one glass fiber can transmit?