Certified Fiber Optics Practice Exam

The core of a multimode optical fiber has a higher refractive index than which part?

1. Cladding

2. Coating

3. Jacket

4. Buffer

The correct answer is: Cladding

In a multimode optical fiber, the core is designed to have a higher refractive index compared to the cladding. This refractive index difference is crucial for the fiber's operation, as it allows light to be guided through the core by total internal reflection. The core's higher refractive index ensures that light entering the core remains confined within it, effectively allowing multiple light modes to propagate simultaneously. The cladding's lower refractive index is specifically formulated to maintain this guiding mechanism by ensuring that any light that reaches the boundary between the core and cladding is reflected back into the core rather than escaping. This property is what enables fiber optics to transmit data over long distances with minimal loss and distortion. The other parts of the fiber, such as the coating, jacket, and buffer, do not play a role in the guiding of light within the fiber itself. They serve protective and structural functions rather than affecting light transmission. Therefore, understanding that the core's higher refractive index relative to the cladding is central to its function is key to comprehending fiber optics principles.