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

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

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

Answer: (A)

Light is guided in an optical fiber because the core has a higher refractive index than the material surrounding it. That difference in index, which comes from differences in material properties (including purity and composition), creates a boundary at the core–cladding interface that reflects light back into the core when it hits at appropriate angles. This reflection keeps the light confined and allows it to travel long distances with little loss. The other layers around the fiber—the buffer, jacket, and coating—are protective sheaths and do not form the guiding boundary that confines light; the reflective boundary responsible for guiding is specifically between the core and the cladding.

Light is guided in an optical fiber because the core has a higher refractive index than the material surrounding it. That difference in index, which comes from differences in material properties (including purity and composition), creates a boundary at the core–cladding interface that reflects light back into the core when it hits at appropriate angles. This reflection keeps the light confined and allows it to travel long distances with little loss. The other layers around the fiber—the buffer, jacket, and coating—are protective sheaths and do not form the guiding boundary that confines light; the reflective boundary responsible for guiding is specifically between the core and the cladding.