EXFO CableSHARK P3 VF/DSL Cable Qualifier - Manual (Page 104)

VF / DSL Cable Qualifier
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8.2.4.6 How to Determine the VOP of a Cable
Calculating the Correct VOP
The exact VOP of a cable of known-length can be determined with the CableSHARK by running a successful
TDR test and reading the time (in ns) between the sent pulse and the reflection pulse from the end of the
cable, regardless of whatever the VOP setting is for the TDR test. Then, the exact VOP of the cable can be
calculated as:
Metric Calculation
VOP = cable length (m) / time reading (s) / light speed / 2
Where the speed of light is 299792458 m/s
Imperial Calculation
VOP = cable length (ft) / time reading (s) / light speed / 2
Where the speed of light is 983559096 ft/s
The division by 2 is due to the return trip that the pulse has traveled.
Determining the Correct VOP
Given a cable of known length, users can determine the correct VOP of that cable. By manually adjusting the
VOP, users can test from both ends of the cable until the CableSHARK measures the exact length of the
cable.
Once the test is set up, press the RUN / STOP key located on the front panel of the CableSHARK to start
the test. Another screen will appear indicating to the user that the TDR test has been started. When a TDR
test is complete, the test result is displayed on the screen.