DCI Testing & Troubleshooting 4 — Questions and Answers
Question 1: What is the TIA-568 maximum allowable permanent link length for Category 6 horizontal cabling?
- 90 meters (Correct answer)
- 100 meters
- 70 meters
- 110 meters
Correct answer: 90 meters
TIA-568 limits the permanent link (from telecommunications outlet to patch panel) to 90 meters, with the remaining 10 meters allocated for patch cords.
Question 2: A technician is troubleshooting intermittent network connectivity. The cable certifies cleanly when tested cold. What should be suspected?
- Thermal expansion causing intermittent contact failure at a connection point (Correct answer)
- Incorrect NVP calibration in the tester
- A permanent open circuit in the cable
- Split pair condition in the horizontal cable
Correct answer: Thermal expansion causing intermittent contact failure at a connection point
Temperature changes can cause marginal terminations to expand and contract, creating intermittent contacts that pass when cool but fail under load or heat.
Question 3: Which tool measures optical power at the end of a fiber to determine insertion loss during an OLTS test?
- Optical power meter (Correct answer)
- OTDR
- Visual fault locator
- Optical spectrum analyzer
Correct answer: Optical power meter
An optical power meter, used with a light source, measures the received power at the far end to calculate insertion loss during Optical Loss Test Set (OLTS) testing.
Question 4: A fiber link passes insertion loss but shows high reflectance. What is the most likely cause?
- Physical contact (PC) connectors that are not properly mating (Correct answer)
- Excessive fiber length
- Incorrect wavelength selection on the test equipment
- A tight bend radius in the fiber
Correct answer: Physical contact (PC) connectors that are not properly mating
Poor physical contact between connector end faces creates an air gap that causes Fresnel reflections, increasing reflectance even if enough light passes for acceptable loss.
Question 5: When performing a wire map test, pins 3 and 6 are shown swapped at the remote end. Which pair is affected?
- Pair 2 (orange) (Correct answer)
- Pair 1 (blue)
- Pair 3 (green)
- Pair 4 (brown)
Correct answer: Pair 2 (orange)
In T568B wiring, pins 3 and 6 carry pair 2 (orange/orange-white); swapping them on the same pair would be a reversal, but if they are from different pairs it is a split pair.
Question 6: A technician must verify fiber polarity in an MPO trunk. Which standard describes the polarity methods A, B, and C?
- TIA-568 (Correct answer)
- ANSI/BICSI 002
- IEEE 802.3
- NEC Article 770
Correct answer: TIA-568
TIA-568 defines MPO/MTP polarity methods A, B, and C to ensure consistent transmit-to-receive alignment across structured cabling systems.
Question 7: What does a 'short' fault on a wire map test indicate?
- Two or more conductors are electrically connected where they should not be (Correct answer)
- The cable is shorter than the minimum required length
- A conductor is broken inside the cable
- The cable fails attenuation due to its short length
Correct answer: Two or more conductors are electrically connected where they should not be
A short (or short circuit) means two conductors that should be electrically isolated are making unwanted contact, often due to a damaged jacket or bad termination.
DCI Testing & Troubleshooting 4
What is the TIA-568 maximum allowable permanent link length for Category 6 horizontal cabling?