Agilent Technologies 86038A User Manual page 206

Programming Commands
Catalog Property
Description Method
206
Returns a list of available curve fits as an array of strings.
Property Value
String() - Contains an array of strings for all the curve fits supported by the
system.
VB.NET Syntax
Dim MyCat() As String
MyCat = odaClient.Analysis.CurveFit.Catalog
VB 6.0 Syntax
Dim MyCat() As String
MyCat = odaClient.Analysis.CurveFit.Catalog
Returns one of the following descriptions, corresponding to the passed-in
short curve fit name.
Linear calculates a single parameter least squares fit. The equation is in the
form: y = Ax + B. It is commonly used for dispersion-shifted fiber, in which
waveguide dispersion is dominant.
Quadratic calculates a second order polynomial fit. The equation is in the form:
2
y = Ax + Bx + C .
3rd Order Sellmeier curve fit is commonly used for dispersion-unshifted fiber,
in which material dispersion is dominant. The equation is in the form:
2 -2
y = A + B + Cx
5th Order Sellmeier curve fit, although more affected by noise and instabilities
in the measurement path, provides more general purpose curve fitting. The five-
term Sellmeier fit can yield multiple zero-dispersion wavelengths. All the values
and their associated slopes are shown in the graphs. The system searches for
dispersion zeros in a wavelength range equaling approximately five times the
measurement span (2.5 times each side of the center wavelength). This allows
identification of zero-dispersion wavelengths which fall outside of the
measurement range. In some cases, due to the peculiarity of the five-term
Sellmeier fit, zero-dispersion wavelengths found outside of the measurement
range may not correspond to actual zero-dispersion wavelengths of the device
under test. The equation is in the form: Ax
4 2
+ Bx
Agilent 86038A Optical Dispersion Analyzer, Third Edition
Base Commands
-2 -4
+ C + Dx + Ex .