Designing and Expanding the Network 2 - 7
The following tables as sist you in obtaining this inf ormation:
❑Table 2-3 - Lists the optical power budget for the 10BASE-FB Mo du le
❑Table 2-6 - List typical losses for conn ector and splice insertion loss
❑Table 2-7 - Lists typical losses for various fi ber cables
Calculating Maximum Link Distance
To calculate the maximum link distance allowed:
1. Determine the optical power budget for the 10BASE-FB
port(Table 2-3).
2. Subtract the optical power l oss due to patch panels and splices
(Table 2-6) from the optical power budget for the 10B ASE-FB port.
3. Subtract the dB loss/km rati ng of the fiber cable (Table 2-7) from the
remainder of step 2. If the result is greater than 0, the link distance is
valid.
4. If the device connecting to the 10BAS E-FB Module does not have the
same optical budget as the 10BASE-FB Mo dule, you must also
calculate the maximum link distance fo r the connecting device.
Determining Link Budget
To ensure link integrity, you should plan for w orst case losses through the
end-to-end optical connection. The optical power budget repres ents a
worst case that assumes the transmitter is transmittin g at the low end of its
range. When possible, 3Com recommends using No rmal power.