I have a basic question about the speed of high-speed channel or I/O and the CMOS technology (aka gate technology). In many papers, I read people are designing or optimizing the design of high-speed channel or I/O like 40 Gbps or any data rate in 0.13 um or 65nm CMOS. In these paper, no one says why they choose that CMOS process technology of the length of the gate in um or nm or whatever. Is there any relation between the speed of I/O and CMOS gate technology? Or in another way to ask, if I want to design 40/50 or even higher Gbps of the channel for I/O what CMOS technology should I consider to implement on as a designer?

Without design innovations, the achievable operation frequency
of circuits is around fT /10. With some design innovations
it is possible to design circuits up to fT /4 or in some cases ft/2.

See paper:

Process and device requirements for mixed-signal integrated circuits in broadband networking

This is just a guide, not a general rule.