ADVANCED ETHERNET CONCEPT
by barkkathulla[ Edit ] 2012-09-18 08:57:26
ETHERNET FIBER OPTICS
The use of the fiber optics in local area networks (LANs), such as Ethernet has increased due to the inherent advantages of using fiber. High data rates can be maintained without electromagnetic or radio frequency interference (EMI/RFI). Longer distances can be achieved over that of copper wiring .For industrial commercial users; fiber offers a high voltage isolation, intrinsic safety and elimination of ground loops in geographically large installations. Ethernet will function with no difficulty over long as some simple rules are followed.
Data transfers over the Medium Independent Interface (MII), defined for Fast Ethernet, are done with 4-bit nibbles that represent actual data with 1oBASE-FL, Manchester encoding is used which guarantees a transition within every bit cell regardless of logic state. This effectively creates a 20 Mbaud signal for a 10 Mbps data rate. If the same encoding were used for Fast Ethernet, a 200 Mbaud signal would result making it difficult to maintain the same 2 km maximum segment length due to bandwidth restrictions. A solution is the 4B/5B code where the 4-bit nibbles being transferred over the Mu are actually encoded as fire-bit symbols sent over the medium.