Airstream Gate 5 Fiber Optic Practice Test

What is the fundamental mechanism that confines light within the core of an optical fiber?

Diffraction at the core boundary Fresnel reflection at the air interface Total internal reflection at the core–cladding interface. Scattering from impurities

Correct Answer:

Total internal reflection at the core–cladding interface.

Explanation:

Light is confined in an optical fiber because it undergoes total internal reflection at the boundary between the higher-index core and the lower-index cladding. When light inside the core hits that core–cladding interface at sufficiently large angles, it cannot refract into the cladding and is reflected back into the core, effectively trapping it and guiding it along the fiber. This requires the core to have a greater refractive index than the cladding, and the angles that allow guiding are described by the critical angle (and related numerical aperture). Diffraction at the boundary and reflections at an air interface don’t provide the sustained confinement the way total internal reflection does, and scattering from impurities mainly causes loss rather than trapping light.

Access more questions from this quiz

Continue to Airstream Gate 5 Fiber Optic Practice Test for more practice questions and the full quiz experience.

Access More Questions