62 Keysight N774-C & 8162-C Series User’s Guide
3 Definition of Terms
Averaging time
Specifies the period during which the power meter or monitor power meter
takes readings from the photo-detector. The displayed power result is the
(arithmetical) average of these readings.
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.
Data logging capability
Maximum number of power readings per port that can be captured during
a logging operation.
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 64, power
expressed in Watts.
Measurement: From the dark measurement result P
i
, a polynomial fit F
i
is
calculated. The fit incorporates the least square-sum difference and uses
3rd-order for the N7744C and N7745C. The Drift D is calculated by
D = max
i
{F
i
} or min
i
{F
i
}, whichever is worse.
Figure 24 Drift (dark)
Conditions: All ports dark. Observation time as specified. Other conditions
as specified.
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