Cisco CCNA (200-301)Network FundamentalsMedium
A company is connecting two buildings that are 3 kilometers apart and requires high bandwidth with immunity to electromagnetic interference. Which cabling type is most appropriate?
- ASingle-mode fiber
- BCategory 6a UTP
- CMultimode fiber
- DCoaxial cable
Show answer & explanationAnswer & explanation
Correct answer: A. Single-mode fiber
Single-mode fiber supports much longer distances (tens of kilometers) than multimode fiber (typically limited to a few hundred meters to about 2 km) and is completely immune to electromagnetic interference, making it ideal for a 3 km inter-building link.
Why the other options are wrong
- B. Category 6a UTP is limited to about 100 meters, far too short for 3 km.
- C. Multimode fiber typically supports only up to around 2 km at high speeds, which may not reliably cover 3 km.
- D. Coaxial cable has limited bandwidth and distance and is rarely used for modern building interconnects.
Single-mode vs Multimode Fiber
Single-mode fiber uses a narrow core and laser light for long-distance, high-bandwidth transmission; multimode fiber uses a wider core and LED/laser light for shorter distances.
- Single-mode: distances up to 40+ km depending on optics
- Multimode: typically under 2 km
- Both are immune to electromagnetic interference
Memory trick: Single-mode goes the single longest distance.