Testing, Troubleshooting, and Documentation
Testing questions reward method. Know the instruments: multimeter, tone generator and probe, cable certifier, OTDR for fiber, and time-domain reflectometer for copper faults. Understand what each test proves-continuity, length, attenuation, crosstalk, return loss-and what it does not. For fiber, know that an OTDR shows events and loss, while an optical power meter shows end-to-end loss. For copper, know that certification differs from verification.
Troubleshooting should be systematic: isolate the segment, verify power, check termination, then test. Common faults include opens, shorts, reversed pairs, split pairs, and water in the jacket. Documentation includes as-builts, test results, labeling, and a record of changes; exam questions often ask what should be delivered at closeout.
Traps: using a certifier to "verify" a link that was never terminated to standard, misreading an OTDR's ghost reflection as a real event, and skipping documentation. Also watch for testing at the wrong reference plane.
Rule of thumb: test the channel as installed, not just the permanent link, and record results against the standard used.
Worked example: a link fails crosstalk. Check termination and pair untwisting first; if the link passes length and continuity but fails NEXT, reterminate and retest before replacing cable.