Keysight Technologies N77 Series User Manual page 61

Specifications and Regulations
Compliance 3
Constant operating conditions
This generally includes constant values of temperature, humidity,
wavelength, input power level, polarization state and mode
distribution, if the quantity is not explicitly subject to variation.
Drift (dark)
Specifies the maximum deviation from zero of the measured power with
no optical input (dark) over time, excluding "Noise pp (dark)" on page
63, power expressed in Watts.
Measurement: From the dark measurement result P , the 3rd order
i
polynomial fit F is calculated. The fit incorporates the least square-sum
i
difference. The Drift D is calculated by
D = max {F } or mini{F }, whichever is worse.
i i i
Figure 42 Drift (dark)
Conditions: All ports dark. Observation time as specified. Other
conditions as specified.
Keysight N77xx Series 61