Agilent Technologies 11896A, User'S And Service Manual

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Choosing the Scan Rate
and Measurement Time
Single wavelength PDL measurements
When using an optical power meter , the scan rate depends on the averaging
time (T) of the instrument. In most applications , the received power is large
enough so a short averaging time can be used. This ensures the fastest
measurement. F or example , the shortest averaging time of the Agilent 8153A
lightwave multimeter power sensor is 20 ms .
Optimum measurements can be made when:
The polarization state generated by the Agilent 11896A does not change
signicantly during the averaging time of the optical power meter .
The polarization state changes fast enough to make the measurement in a
period of time that avoids signicant long term source drift.
When T = 20 ms , a scan rate of 5 is a good choice . A xed measurement
time is sucient for devices with a PDL of <3 dB . A measurement time of
10 sec is sucient to make PDL measurements with an accuracy of 65% (T
= 20 ms , Scan Rate = 5).
T o ensure measurement accuracy of 65%, as the optical power meter
averaging time increases , the scan rate must be decreased and the
measurement time increased. T able A -1 shows combinations of power meter
averaging time , scan rate and measurement time that can be used to ensure a
PDL measurement accuracy of 65%.
A -2