EXFO FVA-600 Guide D'utilisation page 16

Operating the FVA-600 Variable Attenuator
Using the Absolute Mode
The absolute mode displays the current wavelength and attenuation settings.
Note:
The attenuation value is the actual insertion loss between the input and
output ports, including connectors.
Using the Relative Mode
The relative mode displays the current wavelength, the total attenuation, and the
relative attenuation. You need to set a reference before using the relative mode.
Note:
The reference used is the one that was stored for the current
wavelength.
If you vary the attenuation, the total attenuation introduced by the FVA-600 is
displayed in the top right corner, while the relative loss (or gain) with respect to the
selected reference is displayed in dB.
Current
wavelength
10
Attenuation
Relative
attenuation
loss/gain