CompTIA Network+ Preparation · lesson 10 of 30 · 25 min
Copper Cabling
Fiber Optic Cabling
MMF vs SMF
Multimode = Multiple light paths = More dispersion = shorter distance. Singlemode = one path = less dispersion = longer distance. SMF uses laser; MMF uses LED.
Connectors
Cable Issues and Tools
Flashcard Drill
Cat 6A 10 Gbps at 100m — augmented Cat 6, full 10G distance. SMF Single-mode fiber — 9µm core, laser light source, up to 100km+. Long-distance. MMF Multimode fiber — 50/62.5µm core, LED/VCSEL, up to ~2km. Short runs. RJ-45 8-pin copper connector — standard for Ethernet. LC connector Small form factor fiber connector — most common in enterprise. Twinax Twinaxial copper cable — short data center runs (5–7m), 10–100 Gbps. Crosstalk (NEXT) Signal from one wire pair interfering with an adjacent pair. Attenuation Signal loss over distance — all cable types experience it. T568A / T568B Two wiring standards for RJ-45 — must be consistent on both ends (or use crossover). OTDR Optical Time Domain Reflectometer — tests fiber for breaks and attenuation.
Worked Scenario: Cable Selection
Scenario
A network engineer needs to connect two buildings 800 meters apart. The buildings are on the same campus. Which cable type should they use, and why?
Answer: Single-mode fiber (SMF). Copper Ethernet has a maximum distance of 100 meters — far too short for 800m. Multimode fiber supports up to ~2km but is designed for shorter runs within a building or campus. Single-mode fiber supports distances over 100km and is the correct choice for inter-building runs of this length. SMF uses a laser light source and a 9µm core, providing low attenuation over long distances.
If the distance were under 100m, Cat 6A copper would be the most cost-effective choice. If the distance were under 500m within a building, multimode fiber would work. At 800m between buildings, SMF is the right answer.
Knowledge Check — 12 Questions
Cabling & Connectors (Network+)
Which cable category supports 10 Gbps at the full 100m distance?
- Cat 5e
- Cat 6
- Cat 6A
- Cat 7
Answer: Cat 6A
Cat 6A (Augmented) supports 10 Gbps at 100m. Cat 6 only supports 10G up to 55m.
Which fiber type uses a laser and supports distances over 100km?
- Multimode (MMF)
- Single-mode (SMF)
- Twinaxial
- Cat 8
Answer: Single-mode (SMF)
SMF uses a laser light source and supports very long distances — used for WAN and campus backbone.
Which connector is most commonly used for enterprise fiber connections?
- SC
- ST
- LC
- RJ-45
Answer: LC
LC (Lucent Connector) is the most common small form factor fiber connector in enterprise environments.
The standard 8-pin copper connector used for Ethernet is called _____.
Answer: RJ-45
RJ-45 is the standard 8-pin connector for Ethernet (Cat 5e, Cat 6, Cat 6A).
Signal interference between adjacent wire pairs in a cable is called:
- Attenuation
- EMI
- Crosstalk (NEXT)
- Open circuit
- Answer: Crosstalk (NEXT)
NEXT (Near-End Crosstalk) is signal interference between adjacent pairs in the same cable.
Which cable type is used for very short data center runs (5–7m) at 10–100 Gbps?
- Cat 6A
- SMF
- Twinaxial (DAC)
- Coaxial
Answer: Twinaxial (DAC)
Twinaxial Direct Attach Copper (DAC) cables are used for short data center connections at high speeds.
Multimode fiber uses a laser light source.
- True
- False
Answer: False
Multimode fiber uses LED or VCSEL. Single-mode fiber uses a laser.
Which tool tests fiber for breaks and measures attenuation?
- Cable tester
- TDR
- OTDR
- Multimeter
Answer: OTDR
OTDR (Optical Time Domain Reflectometer) tests fiber cables for breaks, splices, and attenuation.
What is the maximum distance for standard copper Ethernet cabling?
- 55m
- 100m
- 150m
- 500m
Answer: 100m
The maximum distance for copper Ethernet (Cat 5e through Cat 6A) is 100 meters.
Signal loss over distance in a cable is called _____.
Answer: attenuation
Attenuation is the weakening of signal strength over distance — all cable types experience it.
Two buildings are 800m apart. Which cable type should connect them?
- Cat 6A
- Multimode fiber
- Single-mode fiber
- Twinaxial
Answer: Single-mode fiber
Copper max is 100m. MMF is ~2km but for long inter-building runs SMF is the correct choice — it supports 100km+ with a laser.
Which multi-fiber connector is used in data centers for high-density connections?
- LC
- SC
- ST
- MPO/MTP
Answer: MPO/MTP
MPO/MTP connectors support 12 or 24 fibers in a single connector — used for high-density data center cabling.
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