2 - 16 ONline Ethernet 10BASE-FL Installation and O peration Guide
This section describes the following scenarios:
❑10BASE-FL Backbone, 10BASE-FL to-the-Desk
❑10BASE-FL Backbone, Unshielded Twisted Pair to-the-Desk
❑10BASE-FB Backbone, 10BASE-FL to-the-Desk
10BASE-FL Backbone, 10BASE-FL to-the-De sk
When designing an all-10BASE-FL netwo rk, keep the following rules in
mind:
1. Limit the longest ideal path between any two network stations to
4200 meters due to the IEEE slottime of 51.2 µsec.
2. Limit the length of an 10BASE-FL segm ent by the optical budget of
the link and the overall size of the network. The 802.3 10BASE-FL
specification sets 10BASE-FL link distances to 2 km. However, you can
generally extend the length if you comp ute the optical budget and
take end-to-end timing into consideration.
3. Each 10BASE-FL Module in a serial path between the two transceiv ers
reduces the maximum cable distance between them by 560 meters
(1836 feet). To be accurate, the equivalent fiber distance is:
❑330 meters for signals that externally enter a 10BASE-FL Module
port and go through the backplane
❑230 meters for signals that internally enter a 10BASE-FL Modu le
using the ONline Concentrator backplane
❑560 meters for signals that externally enter and then exit the
same 10BASE-FL Module
For simplicity, use 560 meters per 10BASE-FL Module in the path,
regardless of the signal's direction, when calculating fiber equivalent
distances. Note, however, that this limits the network diameter to less
than the maximum size.