A network technician is performing diagnostic testing on several physical cabling installations across a enterprise facility. Match each physical layer cabling issue on the left with its underlying root cause or correct remediation on the right.
- High insertion loss and high optical return loss at a fiber optic patch panel junction, with no physical glass break detected.Contaminated connector end-face requiring inspection with a fiber inspection scope and proper optical cleaning.
- A UTP cable run shows 100% pin-to-pin DC continuity on a basic wiremapper, but experiences severe NEXT and corrupted frames at 1 Gbps.Split pair termination where pin assignments maintain DC continuity but break the differential pair twisting.
- Intermittent frame errors and packet loss on a horizontal copper cable run occurring specifically when high-voltage HVAC compressors cycle on.Electromagnetic interference (EMI) disrupting unshielded copper cabling due to proximity to high-current power equipment.
- No physical link light signal detected between two switch SFP modules connected via a newly installed duplex fiber patch cable.Fiber polarity reversal (Tx/Rx crossover mismatch) requiring the LC connector strands to be swapped at one end.
Answer
The physical layer symptoms correspond to their underlying causes as follows: optical attenuation/reflection without break indicates fiber end-face contamination; 100% DC continuity with high NEXT indicates a split pair; intermittent errors during motor startup indicate EMI on UTP runs; and total lack of fiber link light indicates a Tx/Rx polarity reversal.
Each cabling symptom matches standard physical layer troubleshooting principles: end-face dirt causes insertion/return loss; split pairs maintain continuity while generating NEXT; motor operation induces EMI in UTP; and duplex fiber requires proper Tx/Rx crossover alignment.
Step-by-Step Solution
Key Concept
Troubleshooting Physical Cabling and Connectors