Agilent Technologies 86038A User Manual page 101

Setup Menu
Sensitivity/Resolution
Resolution Area
Agilent 86038A Optical Dispersion Analyzer, Third Edition
Trace Points
For Stepped measurement modes
Sets the number of measurement wavelengths including the start and stop
wavelengths. The greater the number of trace points the greater the
measurement accuracy. However, the measurement time also increases.
For Swept measurement mode
Sets the number of trace points to either 801 or 1601.
Increment
Specifies the separation between adjacent measurement wavelengths. In
stepped measurements, it specifies the TLS wavelength step. In swept
measurements, it represents (wavelength range)/ (number of trace points
minus one).
Select a wavelength increment just small enough to reveal the shape
Tip:
of the group delay curve.
RF Mod Freq
Specifies the RF modulation frequency used to modulate the optical signal
in the ODA test set.
In general, a high modulation frequency minimizes instrumentation noise
and a low modulation frequency maximizes wavelength resolution.
Tips on the Modulation Frequency Selection
• If selecting modulation frequency manually, use the selection charts to choose
a combination of wavelength increment and modulation frequency that will
avoid phase wrapping errors and aliasing errors. For example, when measuring
high dispersion fibers in step mode with manual modulation frequency selec-
tion, the use of 2000 MHz modulation frequency may require the selection of a
low wavelength increment to avoid aliasing. This increases test time. To reduce
test time, lower the modulation frequency and increase the wavelength incre-
ment.
• Changing the modulation frequency between normalization and device meas-
urements causes a loss/gain offset due to the frequency response details of the
optical receiver and the network analyzer RF circuitry. This point is true even
when PDA correction is not selected.
Function Reference
101