Operating and Maintenance Instructions –
79
Averaging
Successive traces can be combined to average the results. In IL mode, successive traces are
combined without reference to the polarization state. In PDL mode, traces are averaged for each
of the polarization states individually. The result of averaging is to reduce the effects of white
noise.
To enable averaging, the user enters the weight and number of samples. The weight of the latest
sample is also required. See the
Averages
paragraph in the
How the SWS Calculates Values
section for information on how the averaging is implemented.
Smoothing
Smoothing applies a triangular filter to the data. If the half size chosen for smoothing is n, the
power at any point k is:
P(k) =
∑
P(k+r) (n+1-|r|)
(n+1)
2
where P(k) is the power at point k. The sum is for values of r, from -n to +n, for a half filter size of
n.
The effect of smoothing is to average noise over a few wavelengths. It reduces the wavelength
resolution. Use smoothing with care for devices in which the insertion loss changes rapidly with
wavelength.
Display Type
The display type that can be selected depends on the processing mode. In IL mode, only the
insertion loss can be displayed. However, in PDL mode, there are four possibilities: PDL,
minimum IL, maximum IL, and average IL. Any two can be selected at one time.
•
The minimum IL plotted is the minimum insertion loss at each wavelength for all possible
polarizations of the incident light as it passes through the device. The minimum is computed
from the Mueller matrix, which in turn is derived from the insertion measurements for the four
polarization states that are the output of the polarization controller. The quantities are
computed from the Mueller matrix elements for each wavelength.
•
The maximum IL is the maximum insertion loss, without respect to the polarization state of
the input to the device.
•
The average IL is the average insertion loss over all possible polarization states of the input
to the device.
•
The PDL is the difference between the maximum and minimum insertion losses.
After the selection is made, click the Refresh button to change the display.
Saving a Trace to Memory
A trace that is displayed on the chart can be saved to memory. Press the Save button to save
the trace to memory. Only one trace is saved and the previously saved trace is overwritten.
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
