Agilent Technologies 86038A User Manual page 118

Function Reference
CD Options Area
Smooth
118
Dispersion coefficient can be displayed if the device length has been
measured or specified (See
in the CD trace is divided by the device length (km) to yield the CD
coefficient.
Smoothing controls (averages) the noise without losing too much detail.
The smoothed trace takes over the current trace color and the unsmoothed
(raw) trace is preserved in gray.
Enable Smoothing
When selected, smoothing is turned on.
Algorithm
Boxcar calculates a moving average using an odd number of consecutive data
points centered on each element in the original trace.
Exponential smoothing is applied forward and backward to eliminate a bias. The
traces obtained from each pass are averaged to obtain the result.
Gaussian takes a value for sigma (standard deviation) and applies a point
centered gaussian smooth.
Hanning performs a weighted average smooth where the weights are 25%, 50%,
25% for a 3-point window.
Tips on the Smooth Function
• Be cautious when using smoothing functions, as severe smoothing can affect
the accuracy of the curve fitting process.
• The fact that direct differentiation of the group delay data emphasizes the noise
suggests applying smoothing to the group delay curve before differentiation.
• The combination of moderate smoothing of both the GD trace and the CD trace
may lower the CD trace noise and preserve the CD wavelength resolution better
than smoothing the CD trace alone.
• Refer to "Apply Smoothing to Remove Noise" on page 85
"Length''). If this option is enabled, each value
Agilent 86038A Optical Dispersion Analyzer, Third Edition
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for more information.