Certification testing measures each installed cable link against the performance limits in the cabling standard and produces a pass or fail record for every link. It is the only way to know that new cabling will actually support the speeds its category promises. A simple continuity tester that lights up each wire is not the same thing, and should not be accepted as proof of a Cat 6 or Cat 6A installation.
Three levels of testing
| Type | What it tells you | Use it for |
|---|---|---|
| Verification | Wires are connected in the right order; rough length | Quick checks, moves and changes |
| Qualification | Whether a link can carry a particular network speed | Troubleshooting existing cabling |
| Certification | Whether a link meets every limit in the standard for its category | New installations and warranty |
Only certification testing confirms that an installation meets ANSI/TIA-568 or equivalent requirements. Most cabling manufacturers require a full set of certification results before they will issue a long-term system warranty.
What a copper certification test measures
A certification tester connects to both ends of a link and runs a series of measurements across the full frequency range of the category. Key results include:
- Wire map: each conductor connected to the right pin, with no opens, shorts, crossed or split pairs
- Length: within the limit for the permanent link or channel
- Insertion loss: how much signal is lost along the cable
- Near-end crosstalk (NEXT) and related crosstalk measures: how much signal leaks from one pair to another, usually the most sensitive test of termination quality
- Return loss: signal reflected back by impedance changes, often caused by poor terminations, kinks or tight bends
- Propagation delay and delay skew: how long the signal takes and how evenly the pairs arrive
- DC resistance and resistance unbalance: increasingly important for PoE
Each result is compared with the limit. The tester reports the margin: how far the link passed or failed by. Links that pass by a hair, often marked with an asterisk, are worth a second look.
Permanent link vs channel
The permanent link is the installed cable from patch panel to outlet, tested without the patch cords that will be used later. The channel includes the patch cords. New installations are normally certified as permanent links, because patch cords get changed over the life of the system. Make sure the tester is set to the right test limit and category, with current calibration and correct adapters.
Fibre testing
Fibre links are tested in two ways:
- Basic (Tier 1) testing uses a light source and power meter, or an optical loss test set, to measure total loss and length and confirm polarity. The result is compared with a loss budget calculated for the link.
- Extended (Tier 2) testing uses an OTDR, which sends pulses down the fibre and shows each connector, splice and bend as an event along a trace. It locates problems and documents the link in detail.
Tier 1 testing is usually the minimum for acceptance. OTDR traces are common on backbones, outside plant and long links. Connector end faces should be inspected and cleaned before testing; dirt is a leading cause of fibre failures.
Ask for the native files. A summary sheet of passes proves little. Ask for the full test reports from the tester software, showing each link's identifier, date, test limit, tester serial number and margin. Those records are what a manufacturer warranty claim and future troubleshooting rely on.
What causes failures
- Too much untwisting of pairs at the jack or panel
- Tight bends, kinks, crushed cable or over-tightened cable ties
- Mixed components from different categories or manufacturers
- Runs over the length limit
- Damaged cable from pulling too hard or past sharp edges
- For fibre: dirty connectors, poor splices and tight bends
Most failures are fixed by re-terminating. Some, such as damaged or over-length cable, require a new pull, which is why testing should happen while ceilings are still open where possible.
What to require at handover
- Certification results for 100 percent of links, not a sample
- Results labelled with the same identifiers as the physical labels
- Test limit, cable type and tester calibration shown on each report
- Fibre loss results against a stated budget, plus OTDR traces where specified
- As-built drawings and the manufacturer warranty certificate
Matching identifiers between tests, labels and drawings is covered in cable labelling and documentation. For the standards behind the limits, see structured cabling standards.
How ehZee can help
Verification is the last step in our approach on every project. Our structured cabling design and build service includes testing installed links and handing over the results with the documentation, so you have a record of what was built.
Common questions
Do we need to test every link?
Yes, for new installations. Sampling misses the individual bad terminations that cause intermittent problems later, and warranties generally need full results.
Can old cabling be certified?
It can be tested to a standard, but older cable may not meet current category limits. Qualification testing is often more useful for existing cabling, since it tells you what network speeds it can carry.