Designing and Expanding the Network 2 - 7
Determining Link Budget
As a network planner or installer, account for worst case losses through the
optical connection, end-to-end, to ensure link integrity. The optical power
budget represents a “worst case” assuming the transmitter is transmitting
at the low end of its range.
Adhere to the IEEE 802.3 10BASE-FL specification which states that the
minimum distance supported between two 10BASE-FL ports is 2 kilometers.
If the link between two 10BASE-FL ports is:
❑ Less than 2 kilometers and contains minimal losses (that is, only one
splice or connector and typical fiber cable attenuation) you do not
need to calculate the optical budget for the link.
❑ If you must exceed 2 kilometers, or if you have multiple splices in the
cable, you must calculate the optical power budget.
Note: When connecting a 10BASE-FL product to an FOIRL
product, do not exceed the 1 kilometer maximum distance
defined by the 802.3 FOIRL specification. Because
10BASE-FL is backward compatible with FOIRL, you can
make mixed 10BASE-FL/FOIRL connections. However, to
interoperate 10BASE-FL and FOIRL equipment, observe the
more limiting restrictions of the FOIRL specification.
Table 2-3 provides the Transmit Optical Power ranges and required Receiver
Optical Power sensitivity levels for the 10BASE-FL Module.
