Black Box TS250A, Manual, Page: 34 / 64

Attenuation
Chapter 3 Optical TAPs 34
rev. 1
Determining your power loss budget is a several step process that
requires you to know the send power and receive sensitivities of the
devices connected to the TAP, and requires that you do some basic
math. Use these equations to determine the light available in decibels
at the analyzer.
1
Determine your power loss budget by subtracting the receive
sensitivity of the device connected to Link B from the send power
of the device connected to Link A. Get these values from the
device manufacturers. The amount of loss that you can have
through attenuation and connector loss must be less than this
power loss budget.
(Send Device Power) – (Receive Device Sensitivity) = Power Loss Budget
These values will be negative numbers, so you will be subtracting
a negative number from a negative number and its product will be
a positive number.
2
Determine the loss caused by attenuation. See Table 5 for values
to assist you. If your cables are less than one kilometer, convert
your cable length for the equation.
(Number of Connectors * Connector Loss) + (Fiber Length of Link A *
Fiber Loss) + (Fiber Length of Link B * Fiber Loss) = Attenuation
3
Subtract the output from step 2 from step 1 .
Power Loss Budget - Attenuation = Actual Loss
If the actual loss is less than the power loss budget, then your
budget is feasible with your chosen split ratio; however, you must
also calculate the power loss budget for the analyzer from Link A
and from Link B. Only if both power loss budgets are feasible is
the chosen split ratio usable.
4
Determine your maximum insertion loss by subtracting the
receive sensitivity of the analyzer from the send power from the
device connected to Link A. Get these values from the device
manufacturers. This is the amount of loss that you can have
through attenuation and connector loss.
(Send Device Power) – (Analyzer Sensitivity) = Power Loss Budget
5
Determine the loss caused by attenuation. See Table 5 for values
to assist you.