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Principles of Communication: Optical Fibre MCQ

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Optical FibreMediumQuestion 20318

Question

Single-mode optical fibre has a very small core diameter (8–10 μm) in order to:
  1. A
    Increase modal dispersion
  2. B
    Allow only one mode to propagate, eliminating modal dispersion
    Correct
  3. C
    Reduce manufacturing cost
  4. D
    Increase the acceptance angle

Correct answer

Allow only one mode to propagate, eliminating modal dispersion

Explanation

When core diameter ≈ wavelength (V-number < 2.405), only the fundamental mode propagates. No modal dispersion → much higher bandwidth × distance product (multi-mode: ~500 MHz·km; single-mode: >100 GHz·km). Used for all long-haul (>1 km) links.

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