Optical Fibre

Pick an option to see whether it holds. If one of them stops you, the theory page is two steps back.

1. 01

   Which part of an optical fibre has the higher refractive index?

   • a) Cladding
   • b) Core
   • c) Buffer coating
   • d) Jacket
2. 02

   The basic principle behind light propagation in an optical fibre is:

   • a) Diffraction
   • b) Total internal reflection
   • c) Polarization
   • d) Interference
3. 03

   For total internal reflection to occur at the core–cladding interface, the angle of incidence at that interface must be:

   • a) Equal to the critical angle
   • b) Less than the critical angle
   • c) Greater than the critical angle
   • d) Equal to 90°
4. 04

   The function of the cladding in an optical fibre is to:

   • a) Increase the fibre's mechanical strength only
   • b) Provide the necessary refractive index difference to confine light in the core
   • c) Absorb stray light
   • d) Increase the numerical aperture indefinitely
5. 05

   The acceptance angle of an optical fibre is defined as:

   • a) The angle at which the fibre bends without breaking
   • b) The maximum angle of incidence at the fibre end face for which light undergoes total internal reflection inside the core
   • c) The angle between core and cladding boundary
   • d) The angle of the fibre axis with the horizontal
6. 06

   Numerical aperture (NA) of an optical fibre is given by:

   • a) NA = n₁ + n₂
   • b) NA = sin θ₀ = √(n₁² − n₂²)
   • c) NA = n₁ / n₂
   • d) NA = cos θ₀
7. 07

   The acceptance cone of an optical fibre is:

   • a) The physical conical shape of the fibre core
   • b) The locus of all acceptance angles rotated about the fibre axis, defining the region within which incident light will be guided
   • c) The region where cladding is absent
   • d) The cone-shaped connector used to join fibres
8. 08

   If the numerical aperture of a fibre increases, the acceptance angle:

   • a) Decreases
   • b) Remains unchanged
   • c) Increases
   • d) Becomes zero
9. 09

   A higher numerical aperture generally results in:

   • a) Lower light-gathering capacity but higher bandwidth
   • b) Higher light-gathering capacity but increased intermodal dispersion (lower bandwidth)
   • c) No change in light-gathering capacity
   • d) Complete elimination of dispersion
10. 10

    A step-index optical fibre has core RI n₁ = 1.5 and cladding RI n₂ = 1.4. The numerical aperture is approximately:

    • a) 0.17
    • b) 0.55
    • c) 0.35
    • d) 0.1