Ethernet basics: 10 Base-FL

10 Base-FL is basically a version of Ethernet which runs over fiber optic cable. In physical topology, it is very similar to 10 Base-T.

Cable Type & Network Topology

10 Base-FL runs over 62.5/125 micron multimode fiber optic cable. It supports distances of 2000 meters (6600 feet).

10 Base-FL is wired in a star topology with all of the fiber optic runs originating from a central hub. It is also acceptable to connect a pair of 10 Base-FL devices directly together with a point to point link.

One point which must be made is that although 10 Base-FL links can be run up to 2000 meters, an Ethernet network has an overall maximum network diameter (distance between the two most widely separated nodes) of 2500 meters. Therefore, it is highly reccomended that anyone planning to install a long 10 Base-FL cable run checks the overall network to ensure that adding the new run does not exceed the overall network size. If the overall size will exceed 2500 meters, then a local Ethernet bridge or a switch will need to be installed to split the network into multiple subnetworks, each of which can be built to the full 2500 meter limit.

Applications

Since 10 Base-FL uses fiber optic cable, it is completely immune to any type of external electrical interferance. This makes it a very attractive technology for use in areas such as factory floors where electromagnetic interferance (EMI) levels are very high. Another property of fiber optics is that fiber is very difficult to tap into, thus providing a high level of security. Finally, 10 Base-FL is very useful for use in interconnecting buildings in a campus environment wehre distances could be very long.