Agilent Technologies 86038A User Manual page 67

Choosing Setup Parameters for Your Device
Agilent 86038A Optical Dispersion Analyzer, Third Edition
Fiber Bragg Grating Dispersion Compensators
Characteristics
• High dispersion (steep change in group delay versus wavelength)
• Group delay ripple (fine structure in the group delay curve)
Measurement Tips
• If the group delay ripple is to be measured, it is necessary to select a small
enough modulation frequency and wavelength interval to resolve the ripple.
• The swept mode offers very small wavelength intervals and high measurement
speed. The step mode may take an unacceptable amount of time if the wave-
length step is very small and the wavelength range is large.
• When measuring in step mode in cases where the group delay ripple is not re-
quired, manually select a modulation frequency and wavelength step appropri-
ate to the maximum expected level of dispersion. Automatic modulation
frequency selection may not be reliable in cases of high group delay ripple.
• Manual selection of the modulation frequency allows the use of the Phase Dy-
namic Accuracy (PDA) correction process in the step mode. The PDA correction
feature is available only at the single modulation frequency at which the normal-
ization was performed. PDA correction is available in the swept mode, as the
swept mode always operates at a single, user-selected modulation frequency.
• Of the built-in curve fits, only the linear fit is likely to be useful in this application.
Use it when the entire trace is to be fitted and the group delay ripple is required.
Export the data to a spreadsheet and subtract the fitted straight line from the
measurement data to obtain the group delay ripple.
Making Measurements
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