Keysight N778xC Series Polarization Instruments User’s Guide 51
Definition of Terms 3
PMD Measurement Range
Specifies the range of DUT PMD values for which the instrument measures
PMD values not disturbed by aliasing effects. This value applies for highly
mode-coupled devices such as single mode fibers. For non-mode-coupled
devices such as polarization maintaining fibers (PMFs), the PMD
measurement range equals the DGD measurement range.
Polarization Dependent Loss (PDL)
The dependence of the loss of a device on the input polarization state,
calculated as the difference between maximum and minimum loss (both
in dB).
Polarization Dependent Loss (PDL) Uncertainty
Specifies the uncertainty of the measurement results for polarization
dependent loss, expressed as the sum of an offset and a standard
deviation.
The offset is calculated by the difference of the mean value of the golden
device data and the mean value of the measured data, both mean values
calculated over the wavelength.
The standard deviation over wavelength is calculated from the deviations
around a calibration line shifted by this offset, again over wavelength.
Polarization Dependent Loss (PDL) Repeatability
The agreement of repeated measurements of PDL on a stable test device
and under constant environmental conditions.
These measurements are performed over the defined wavelength range.
For each wavelength the repeatability is calculated by:
PDL_repeat = 2 * { PDL
j
– (PDL
max
+ PDL
min
) / 2 }, with j = number of repetitions
The PDL Measurement Repeatability is the maximum of all PDL
repeatability’s over wavelength after excluding one out of 1000
PDL-values and smoothing over 3 neighboring wavelength values.
Polarization Dependent Loss (PDL) Range
Specifies the maximum PDL which can be measured.
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