Full-duplex Gigabit Ethernet is used today. It is entirely natural to use the full-duplex Ethernet protocol because, down at the physical level, both the fiber optic and copper gigabit implementations transmit signals in both directions concurrently. Chapter 9 and Appendix A discuss how this is done.
Full-duplex Ethernet was described in Chapter 5, "Full-Duplex Ethernet Communication." There is nothing complicated about it:
CSMA/CD is not used. Full-duplex mode is used on links for which there are no collisions.
A system can send a frame whenever it wants, except for the fact that frames must be separated by an interframe gap and PAUSE requests must be honored.
Full-duplex communication at 1000Mbps is no different ...