Certified Fiber Optics Practice Exam

Graded index fibers primarily reduce what factor to improve signal quality?

1. Intermodal delay

2. Scattering

3. Refraction

4. Absorption

The correct answer is: Intermodal delay

Graded index fibers are designed specifically to minimize intermodal delay, which is the difference in travel time between various modes (or paths) of light within the fiber. In these fibers, the refractive index gradually decreases from the center towards the cladding, allowing light rays that enter at different angles to travel the same effective distance. This design leads to reduced modal dispersion, thus improving the overall signal quality as it allows multiple light modes to arrive at the receiver simultaneously and in phase. By reducing intermodal delay, graded index fibers become particularly effective for long-distance transmissions where maintaining signal integrity is critical. The improvement in signal quality minimizes the chances of overlapping signals, which can degrade data transmission efficiency. Consequently, though scattering, refraction, and absorption are all important factors in fiber optics, they do not directly relate to the primary enhancement that graded index fibers provide, which specifically targets intermodal delay.