Agilent Technologies 86038A User Manual page 66

Making Measurements
66
Fiber Dispersion Compensating Module (DCM)
Characteristics
• High dispersion (steep change in group delay versus wavelength).
• Broadband device
• Significant loss
• The zero dispersion wavelength falls far outside the 1500 nm window.
Measurement Tips
• For higher loss fibers, improve signal-to-noise by using a narrower IF bandwidth
and a larger number of samples.
• When measuring in step mode, use the automatic modulation frequency selec-
tion feature or manually select a modulation frequency and wavelength step ap-
propriate to the expected level of dispersion. Both strategies will eliminate the
possibility of RF phase wrap errors.
• 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.
• When measuring high dispersion fibers in step mode with manual modulation
frequency selection, 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 increment.
Choosing Setup Parameters for Your Device
Agilent 86038A Optical Dispersion Analyzer, Third Edition