200-150 · Question #230
Which types of cable do you use to connect two Cisco switches that are 50 km apart?
The correct answer is D. SMF. At 50 km, only single-mode fiber can provide the low attenuation and minimal dispersion needed to sustain the optical signal over that distance.
Question
Which types of cable do you use to connect two Cisco switches that are 50 km apart?
Options
- AUTP
- BSTP
- CMMF
- DSMF
How the community answered
(58 responses)- A3% (2)
- B2% (1)
- C2% (1)
- D93% (54)
Why each option
At 50 km, only single-mode fiber can provide the low attenuation and minimal dispersion needed to sustain the optical signal over that distance.
UTP copper has a maximum segment length of 100 m for Ethernet and cannot span 50 km under any standard.
STP copper is also limited to 100 m maximum and is electrically incapable of transmitting over kilometer-scale distances.
MMF supports roughly 300-550 m at 10G (OM3/OM4) due to modal dispersion; 50 km far exceeds its usable range.
SMF uses a 9-micron core that propagates light in a single mode, virtually eliminating modal dispersion and allowing transmission over 40-80+ km with appropriate long-reach optics such as the CWDM or DWDM transceivers Cisco supports for extended distances.
Concept tested: Fiber media selection for long-distance switch interconnects
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet/10561-fiber.html
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