seriallie over coaxial cable

To use available high speed IO transceivers with coaxial cables, you would need two cable pairs for each lane. This replacement of a 100 ohm differential pair by two single ended 50 ohm cables is sometimes done for SATA, SAS or PCIe, mainly in a lab for test and measurement. At the lower bandwidth corner of high speed serial links (< 1GBit/s), you can try transformer coupling or active drivers to adapt single ended cables for the link.