EXFO IQS-1700 High Performance Power Meter for IQS-500/600 - Manual (Page 51)

High Performance Power Meter 43
6 Measuring Power
Power measurements can be displayed in two ways:

absolute

relative
It is also possible to use a correction factor at specific wavelengths and to
add an offset value to your power measurement.
Displaying Absolute Power
When in absolute power, measured values are displayed in either dBm or
W units (pW, nW, W, mW...) and the displayed value represents the
absolute optical power reaching the detector within specified uncertainty.