DCI Testing and Certification 5 — Questions and Answers
Question 1: A Category 6 permanent link fails the NEXT test at high frequencies. Which corrective action is MOST likely to resolve this?
- Replace the cable with a larger diameter conductor
- Re-terminate the connectors to reduce untwisting at the termination point (Correct answer)
- Increase the pull tension to remove slack from the cable run
- Add a grounding conductor between the patch panel and the jack
Correct answer: Re-terminate the connectors to reduce untwisting at the termination point
Excessive untwisting at connector terminations is the most common cause of NEXT failures; reducing untwisted length to the minimum required per manufacturer spec typically resolves the issue.
Question 2: What is the purpose of 'reference cords' when performing an OLTS fiber test using the one-cord reference method?
- To extend the OLTS range to 100 km links
- To establish a baseline loss measurement that zeroes out the test cord losses (Correct answer)
- To measure the back-reflection of the fiber connectors
- To synchronize the light source and power meter wavelengths
Correct answer: To establish a baseline loss measurement that zeroes out the test cord losses
Reference cords are used to zero the power meter so that only the losses of the link under test (connectors and cable) are measured, not the losses of the test equipment cords.
Question 3: Which BICSI credential is specifically designed for professionals who install and test structured cabling systems?
- RCDD (Registered Communications Distribution Designer)
- TECH (Technician) (Correct answer)
- DCDC (Data Center Design Consultant)
- OSP (Outside Plant Designer)
Correct answer: TECH (Technician)
The BICSI TECH credential is targeted at technicians who install and maintain telecommunications distribution systems, including cabling installation and testing.
Question 4: An OTDR dead zone prevents detection of events close to the launch end. What is the standard method to work around this limitation?
- Use a higher-power OTDR launch pulse
- Use a launch cable (mandrel or launch lead) to move the dead zone away from the link under test (Correct answer)
- Test only from the far end of the fiber
- Switch from multimode to singlemode OTDR
Correct answer: Use a launch cable (mandrel or launch lead) to move the dead zone away from the link under test
A launch cable (also called a mandrel or launch lead) of known length is connected before the link under test, pushing the dead zone onto the launch cable rather than the link being certified.
Question 5: What is the maximum allowable DC loop resistance for a 24 AWG Category 6 horizontal cable run of 90 meters?
- 9.38 Ω (Correct answer)
- 19.2 Ω
- 25 Ω
- 40 Ω
Correct answer: 9.38 Ω
Per TIA-568, the maximum DC resistance for 24 AWG solid copper conductors at 90 meters (permanent link) is approximately 9.38 Ω, which is verified during certification testing.
Question 6: A contractor submits a certification report showing all links passed with a Level III tester. What does 'Level III' signify?
- The tester is rated for Category 3 cable only
- The tester meets the accuracy requirements for certifying up to Category 6A and Class EA cabling (Correct answer)
- The tester has three independent test ports
- The tester was manufactured to IEC Level III quality standards
Correct answer: The tester meets the accuracy requirements for certifying up to Category 6A and Class EA cabling
IEC 61935-1 defines tester accuracy levels; Level III (or Level IIIe) accuracy is required to certify Category 6A/Class EA cabling at 500 MHz with sufficient measurement uncertainty margins.
Question 7: Which condition would cause a cable certification tester to report a 'FAIL* ' (fail with asterisk) result rather than a standard 'FAIL'?
- The cable exceeds the maximum channel length
- One or more measurements fell within the tester's measurement uncertainty margin near the limit (Correct answer)
- The wire map shows a crossed pair
- The cable temperature exceeded 60°C during testing
Correct answer: One or more measurements fell within the tester's measurement uncertainty margin near the limit
A FAIL* result indicates marginal performance where the measurement is within the tester's accuracy uncertainty range of the limit, meaning the link could potentially pass with a more accurate instrument.
DCI Testing and Certification 5
A Category 6 permanent link fails the NEXT test at high frequencies.
Which corrective action is MOST likely to resolve this?