Agilent Technologies 86038B, Руководство пользователя

Страница: 85 / 350

Agilent 86038B Photonic Dispersion and Loss Analyzer, Second Edition
85
Choosing Setup Parameters for Your Device
A list of characteristics, suggestions and relationships are
provided for a variety of device types. For more information on
the measurements that you can make, refer to “Measurement
Concepts” on page 49 . For more information on the instrument
functions, refer to “Function Reference” on page 93 .
Transmission Fiber (All Types)
Characteristics
• Large range of dispersion values across the wavelength range
• Wide wavelength range of interest
• Smoothly changing group delay with relatively little fine
structure with respect to wavelength
• Group delay is easy to curve fit using conventional model
curves
• Differential group delay (DGD) may exhibit multiple peaks
and valleys
• Approximately 0.25 dB/km attenuation
Measurement Tips
The relatively smooth and analytic behavior of the group delay
of this device makes it possible to use larger wavelength
increments and higher modulation frequency without concern
for loss of wavelength resolution.
A good choice is 2 GHz, as used for the specifications.
Wavelength increment may be large, like 0.5 nm or more, except
if a high CD level requires closer steps to avoid phase wrapping.
If the PMD is higher than about 10ps, then steps smaller than
0.5 nm should also be chosen for the DGD measurement,
because the rate at which the DGD of a fiber changes with
wavelength is proportional to the PMD.
It is also useful for the PMD result to measure over a wide
wavelength range, even if the fiber is only used in a more limited
range, because the wider range will give a better average value.