also known as 1000Base-F, is a physical layer baseband specification for Ethernet communications over optical fibers. 1000Base-F uses 8B/10B ANSI X3T11 Fibre Channel FC-1 frame encoding, serializer/deserializer (SERDES) and NRZ on the fiber, clocked at 1250 Mbaud. 1000BaseF can support a fiber cable length of 500m full duplex on multimode fiber fiber, and of 2-3km full duplex on single mode fiber. IEEE Specification: IEEE 802.3z