The core of optical fiber carries the modulated light signals.

• A. Buffer
• B. Cladding
• C. Outer jacket
• D. Core

Answer: (D)

The essential idea is that light signals are guided through the inner region of the fiber called the core. The core is made of glass with a higher refractive index, which keeps the light trapped inside by total internal reflection at the boundary with the surrounding cladding (which has a lower refractive index). This arrangement lets the modulated light travel long distances with minimal loss, carrying the data. The surrounding cladding simply provides the boundary that keeps the light in; the buffer coating and outer jacket are protective layers that shield the fiber from damage and environmental factors. So, it’s the core that actually carries the modulated light signals.