Agilent Technologies 86038A User Manual page 104

Function Reference
Sensitivity Area
104
When using both ports and auto modulation frequency, connect the
Tip:
device with the largest dispersion to port 1.
IF Bandwidth
Sets the bandwidth of the filtering process that trades off measurement
noise floor (sensitivity) against measurement speed. A lower IF bandwidth
value means lower noise (high sensitivity) and a longer measurement time.
Reduce the IF bandwidth as needed to control trace noise. This is
particularly important when measuring a high insertion loss device.
"Smooth''.
Tips on IF Bandwidth Selection
• For higher loss (typically longer) fibers, improve signal to noise by using a nar-
rower IF bandwidth. Expect to trade-off measurement speed.
• When making PDL or DGD measurements, the polarization scanner runs at a
fixed speed and produces PDL or DGD changes with the majority of spectral
content around 8 Hz. This limits the minimum IF bandwidth when scanning to
70 Hz, which avoids attenuating the 8 Hz components. Using a wider IF band-
width allows a faster measurement, but raises the noise in the measurement
and may slightly bias DGD and PLDL toward larger values.
• During PDA normalization, 70 Hz IF bandwidth is used to characterize noise
components with the scanner off, for both GD and Magnitude. These noise
measurements provide the best correction to DGD and PDL when measuring 70
Hz IF bandwidth. For more information on PDA,
refer to "Phase Dynamic Accuracy" on page
Samples/Point
Determines the number of amplitude and phase measurements (samples)
that are taken at each measurement wavelength (trace point).
In the Swept measurement mode the samples per point is always 1.
In Stepped measurement modes, you select how many samples to take at
each measurement wavelength. The multiple samples are averaged to
generate a single trace point. A larger number of points means more
averaging, suitable for reducing trace noise in cases of high insertion loss
test devices. Large number of points improves the polarization mode
coverage to provide more accurate DGD and PDL. Note that a large number
of samples increases susceptibility to drift.
Tips on Number of Samples
• In stepped mode, use a larger number of samples to improve signal to noise. Ex-
108.
Agilent 86038A Optical Dispersion Analyzer, Third Edition
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