In a duplex LC fiber link, what does flipping polarity accomplish when incorrect polarity causes no light on straight-through?

• A. Degrades signal quality further.
• B. Changes color coding.
• C. Flipping polarity restores light on straight-through runs.
• D. Has no effect.

Answer: (C)

In a duplex fiber link, light must travel from the transmitter on one end to the receiver on the other. If polarity is incorrect, the transmitter’s path can end up feeding the wrong fiber at the far end, so the receiver doesn’t see light on a straight-through connection. Flipping polarity swaps the two fiber paths at one end, realigning the transmitter with the correct receiver. Once this mapping is corrected, the link can light up on straight-through runs. This action does not change color coding and does not inherently degrade signal quality; it simply fixes the fiber-to-fiber mapping so the link works.