C7 Signal Transmission & Cabling Techniques 3 — Questions and Answers
Question 1: A fiber optic link has a calculated loss budget of 3.5 dB. The measured insertion loss is 4.2 dB. What is the correct action?
- The link passes; 4.2 dB is within typical tolerances
- The link fails; investigate connectors, splices, and bends (Correct answer)
- Add an optical amplifier to compensate
- Re-label the link as single-mode to allow higher loss
Correct answer: The link fails; investigate connectors, splices, and bends
Measured loss exceeding the calculated budget means the link fails and must be troubleshot for dirty connectors, bad splices, or excessive bend radius violations.
Question 2: Which cable standard governs the installation of optical fiber in commercial buildings in the United States?
- IEEE 802.3
- ANSI/TIA-568.3-D (Correct answer)
- ISO/IEC 11801
- NEC Article 725
Correct answer: ANSI/TIA-568.3-D
ANSI/TIA-568.3-D specifies optical fiber cabling components and transmission performance for commercial building telecommunications.
Question 3: What is the bend radius rule of thumb for a Cat 6A patch cord during installation?
- 4 times the cable diameter
- 8 times the cable diameter (Correct answer)
- 10 times the cable diameter
- 4 times the cable diameter only when pulling
Correct answer: 8 times the cable diameter
TIA-568 recommends a minimum bend radius of 8 times the cable outer diameter for Cat 6A patch cords.
Question 4: In a daisy-chain video surveillance installation, which cabling topology causes signal degradation for cameras at the end of the chain?
- Star topology
- Series/daisy-chain topology (Correct answer)
- Ring topology
- Hierarchical star topology
Correct answer: Series/daisy-chain topology
Daisy-chaining loads the source with cumulative impedance mismatches, causing reflections and voltage drop for downstream devices.
Question 5: A technician is testing a newly installed twisted-pair run and finds a 'split pair' fault. What caused it?
- A broken conductor inside the cable jacket
- One wire from each of two different pairs was terminated together (Correct answer)
- Excessive pulling tension during installation
- An improper punch-down tool depth setting
Correct answer: One wire from each of two different pairs was terminated together
A split pair occurs when conductors from different pairs are cross-terminated, destroying the pair's mutual cancellation and severely increasing crosstalk.
Question 6: Which parameter describes the ratio of reflected signal power to incident signal power at an impedance discontinuity?
- Insertion loss
- Return loss (Correct answer)
- Propagation delay
- Attenuation-to-crosstalk ratio (ACR)
Correct answer: Return loss
Return loss measures how much signal is reflected back toward the source due to impedance mismatches, expressed in dB.
Question 7: When pulling cable through conduit, what is the maximum recommended fill ratio to avoid damage?
- 25%
- 40% (Correct answer)
- 53%
- 80%
Correct answer: 40%
NEC Chapter 9 and BICSI guidelines recommend a 40% fill ratio maximum for conduit to allow future cable additions and prevent installation damage.
C7 Signal Transmission & Cabling Techniques 3
A fiber optic link has a calculated loss budget of 3.5 dB.
The measured insertion loss is 4.2 dB.
What is the correct action?