Practical TCP/IP and Ethernet Networking for Industry

Fast and gigabit Ethernet systems 69

4.4.3 Physical medium independent (PHY) sub layer

The 802.3z Gigabit Ethernet standard used the three PHY sub layers from the ANSI

X3T11 fiber channel standard for the 1000Base-SX and 1000Base-LX versions using

fiber optic cable and 1000Base-CX using shielded 150-ohm twinax copper cable.

The Fiber Channel PMD sub-layer ran at 1 Gbaud and specifies the 8B/10B coding of

the data, data scrambling and the non return to zero – inverted (NRZI) data coding

together with the clocking, data and clock extraction processes. This translated to a data

rate of 800 Mbps. The IEEE then had to increase the speed of the fiber channel PHY

layer to 1250 Mbaud to obtain the required throughput of 1 Gbps.

The 8B/10B technique ...