EXFO IQS-3150 Variable Attenuator for IQS-500/600 - Manual (Page 29)

Setting Up Your Variable Attenuator
Variable Attenuator 23
Basic Settings
Setting the B Value
The B value settings are necessary for the X+B display mode. These
settings apply to one or many wavelengths defined in the Wavelength list
and are only enabled when using this display mode. The B value settings
are available for both standard and self adjusting modules.
The B value is defined as a correction factor or defined as an input power
value representing the attenuation in the equivalent output power in dBm.
Correction Factor
The Correction factor is available for both Attenuation and Output Power
control modes. This feature can be used to correct a difference in
attenuation or output power from the original specification due to some
changes in the equipment, such as a connector replacement.