In an optical fiber cable, a reflective boundary is created by the difference in purity between the core and the ______.

In an optical fiber cable, a reflective boundary is created by the difference in purity between the core and the ______.

• A. Cladding
• B. Jacket
• C. Buffer
• D. Sheath

Answer: (A)

Light is guided in an optical fiber by total internal reflection at the boundary between a higher-refractive-index core and a lower-refractive-index cladding. The difference in purity between the core and the cladding leads to a difference in their refractive indices: the purer core has a higher index, while the cladding, with different impurities, has a slightly lower index. When light inside the core hits the core–cladding boundary at a steep enough angle, it reflects back into the core rather than escaping, keeping the light confined along the length of the fiber. The outer layers—buffer, jacket, and sheath—are protective and do not form the reflective boundary that confines the light.

Light is guided in an optical fiber by total internal reflection at the boundary between a higher-refractive-index core and a lower-refractive-index cladding. The difference in purity between the core and the cladding leads to a difference in their refractive indices: the purer core has a higher index, while the cladding, with different impurities, has a slightly lower index. When light inside the core hits the core–cladding boundary at a steep enough angle, it reflects back into the core rather than escaping, keeping the light confined along the length of the fiber. The outer layers—buffer, jacket, and sheath—are protective and do not form the reflective boundary that confines the light.