Agilent Technologies 86038B User Manual page 126

126
Algorithm
Boxcar calculates a moving average using an odd number of
consecutive data points centered on each element in the original
trace.
smoothing calculates each smoothed point as a
Exponential
weighted average of the measured trace points, where the
contribution of each point, offset from the wavelength of the
smoothed point, is reduced by the Weight factor with respect to
the next closer point. The smoothing is applied both forward
and backward to eliminate a bias.
takes a value for sigma (standard deviation) and applies
Gaussian
a point centered gaussian smooth. The slider sets the value of
sigma in units of the wavelength interval.
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 a succeeding 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.
Window
Use the slide bar to select the number or weight of consecutive
trace points that are processed to yield one smoothed point (at
the center of the Window). The smoothing process is repeatedly
centered on each trace point.
Hide Original Trace
Removes the original trace from the graph so that only the
smoothed trace is visible.
Agilent 86038B Photonic Dispersion and Loss Analyzer, Second Edition