Coaxial and Fiber Cable Installation and Testing
Coaxial and Fiber Cable Installation and Testing
This domain tests hands-on installation quality and proof-of-performance testing for coax and fiber. Expect connector preparation, bend radius, grounding, coax sweep/TDR, fiber cleaning, splice loss, power-meter testing, OTDR traces, and loss budgets.
Core rules and concepts
- Coax has a center conductor, dielectric, shield, and jacket. Prepare the connector so the dielectric is flush, no braid touches the center conductor, and the connector is compressed with the correct tool. Over-tightening or a stray shield strand creates ingress and reflections.
- Support cable, respect bend radius, use drip loops, and bond/ground at the premises entry per code. Test with a sweep or TDR; a suck-out or impedance mismatch shows as a reflection.
- Fiber is single-mode or multimode; connectors are UPC or APC, and APC has an angled ferrule. Clean every connector before mating, inspect with a scope, and never look into a live fiber.
- Fusion splicing and OTDR testing require a launch/receive cable to see near-end events; know dead zones and bidirectional testing.
Worked example
A 3 km single-mode link has 0.35 dB/km fiber loss, two connectors at 0.3 dB each, and two splices at 0.1 dB each. Fiber = 3 × 0.35 = 1.05 dB. Connectors = 0.6 dB. Splices = 0.2 dB. Total = 1.85 dB. Add a 3 dB margin: 4.85 dB required. If the budget is 10 dB, the link passes with 5.15 dB spare.
Traps that cost marks
Dirty connectors; mating APC to UPC; using an OTDR without a launch cable; over-polishing or over-tightening; testing fiber while it is live; forgetting that coax shield integrity controls ingress.