2 - 14 ONline Ethernet 10BASE-FB Module Installati on a n d Operation Guide
3. Use Table 2-7 to determine the worst cas e loss for the 50/125 fiber
cable (2000 meters x 5 dB = 10.0 dB). Add the dB losses to
determine total path loss. The tota l path loss is 11.5 dB.
The 11.5 dB optical los s exceeds the optical pow er budget of 5.5 dB.
Therefore the link will not work and the 10BASE -FB Module Port
Status LED will signal a Low Light condition.
Thus, you must use High Power mode. W hen you use High power
(see Table 2-4), the optical power budget of 1 3.5 dB is sufficient to
handle the 11.5 dB path loss.
Choosing a Network Backbone Cabling Structure
Because of fiber's long-distance capabilities and immunity to noise, 3Com
strongly recommends using fiber as the backbone. You can choose
between two fundamental configurat ion topologies when connecting your
network backbone using 10BASE-FB Modules in an ONl ine System
Concentrator:
❑Star Configuration
❑Serial Configuration