Engineering Office

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EXFO FTB 400 with
FTB 5800 CD-Analyzer

For the test of Chromatic Dispersion (CD) we use equipment of EXFO, which consist of the light source FLS 5834 at the far end and at near end the mainframe FTB 400 together with the CD-Analyzer FTB 5800. To measure CD this equipment is using the Phase-Shift-Method. Compared to the OTDR-method with 4 wavelengths, you will receive more accurate results and reflectance on the link (e.g. patch) has no influence on the results.
The dynamic of 42 dB is well enough to make tests on very long backbone links. The chromatic dispersion is the result of material dispersion and waveguide dispersion. Chromatic dispersion is causing pulse lengthening, which is a problem for DWDM-systems. The chromatic dispersion could be reduced for example passive by using compensating fibers. This easy solution is for the reduction of PMD not possible.

Light source for PMD
and CD-testing
EXFO, FLS 5834

The test will be performed in the C- and L-Band. The step width and averaging time can be set manually. Documentation will be done with the EXFO-software “FastReporter”. You will receive the trace for CD together with the Relative Group Delay and of course a list with the values for CD, RGD, Coefficient and slope. For the right coefficient it’s very important to have the exact length of the cable (OTDR-test must be done first).

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