EXFO IQS-12002B Calibration System - Manual (Page 68)

Calibration Methods
64 IQS-12002B
Power Meter
To measure nonlinearity:
1. Set the attenuators in the two paths so that the power measured on the
meter is the same whether the light is coming from branch a or from
branch b.
2. Open both shutters and measure the total power from both branches
simultaneously: P
total,i
.
3. Close the shutter on branch b and measure the power on branch a:
P
a,i
.
4. Close the shutter on branch a, open the shutter on branch b, and
measure the power on branch b: P
b,i
.
5. Add the individual power measurements.
If the sum is not equal to the total power measurement, the DUT
presents nonlinearity.
:
6. Using the first attenuator, attenuate the total power by the following
factor to the level of the sum of the individual power measurements
calculated in step 5.
7. Repeat steps 2 through 6 to cover the desired range.
(dB) log 10
i b, i a,
i total,
10 i P P
P
NL
+
× =
10 2 log 3,01 dB ≅