Signalling and communicationQuestion 242 of 1506

Why does a pulse become stretched in a long run of multimode fibre?

  1. Noise from nearby motor cables
  2. Light on longer paths arrives later
  3. Copper wires inside the cable add inductance
  4. Heat in the glass slows the light
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Correct answer: Light on longer paths arrives later

Light that takes a shorter path reaches the detector sooner than light on longer paths. This blurs the edges of the pulse.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 14.5: Optical Data Communication

Practice signalling and communication

Questions last reviewed: 18 October 2026