EXFO IQS-12004B DWDM Passive Component Test System for IQS-500 - Manual (Page 101)

Interpreting the DWDM Passive Component Test System Results
DWDM Passive Component Test System 89
Optimizing Performance
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Different connector types
Often it will be necessary to test components with different connector
types. To do this, you will have to change the launch fiber (or to use a
hybrid adapter) and you will also have to change the fiber-optic
adapters (FOAs) on the IQS power meters. In this situation, it will be
necessary to perform a new reference measurement and, for truly
optimum results, repeat the spectral response calibration. This is
because different FOAs have slightly different alignment characteristics
(manufacturing tolerances), and this will contribute to an increase in
measurement uncertainty. This also applies when switching from APC
to PC connector types.
Return Loss Errors
Most of the factors affecting IL and PDL also affect the return loss accuracy.
There are, however, some additional factors that should be considered.
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Power budget
A return loss measurement is generally a very low power
measurement. In order to have good accuracy when measuring weak
reflections, it is important to have as much power as possible. One way
of improving the ORL sensitivity and accuracy is to bypass the optional
IQS-5150 PSA. This will give an additional 5 to 8 dB sensitivity as well as
better accuracy and resolution.
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Calibration reference
The calibration reference supplied with the DWDM Passive
Component Test System is used as an absolute reflection reference
based on the glass-to-air interface reflection of 4% (–14.7 dB). When
performing measurements, a different launch cable is used. The
insertion loss of the WRM output connector/launch fiber connector will
not be exactly the same as the insertion loss of the WRM output
connector/reference fiber connector. This difference contributes
directly to the ORL measurement error. For this reason, it is important
to use launch fiber with a good quality connector.
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