CompTIA Network+ (N10-009)Networking ConceptsMedium
A company is running fiber optic cable between two buildings located 8km apart on the same campus. Which fiber type is best suited for this long-distance run?
- ASingle-mode fiber with laser source
- BCat 6a twisted pair
- CCoaxial cable RG-6
- DMultimode fiber with LED source
Show answer & explanationAnswer & explanation
Correct answer: A. Single-mode fiber with laser source
Single-mode fiber uses a laser light source and a narrow core, allowing signals to travel much longer distances (tens of kilometers) with less attenuation than multimode fiber, which is typically limited to a few hundred meters to about 2km.
Why the other options are wrong
- B. Cat 6a copper cable is limited to about 100 meters for 10GBASE-T.
- C. Coaxial cable is used for shorter runs like cable internet and does not support 8km distances.
- D. Multimode fiber suffers modal dispersion and is generally limited to shorter distances (up to ~2km).
Single-Mode vs Multimode Fiber
Single-mode fiber has a small core and uses a laser to transmit light over long distances (up to 100km+), while multimode fiber has a larger core, uses LEDs, and is suited for shorter distances (typically under 2km).
- Single-mode fiber commonly appears yellow
- Multimode fiber commonly appears orange or aqua
- Single-mode supports higher bandwidth over longer distances
Memory trick: Single-mode = single laser beam goes the distance