Certified Fiber Optics Practice Exam

Single mode fibers have a core that is:

1. Larger than multimode fibers

2. The same size as multimode fibers

3. Smaller than multimode fibers

4. Nonexistent

The correct answer is: Smaller than multimode fibers

Single mode fibers are designed with a core that is significantly smaller than that of multimode fibers, typically around 8 to 10 micrometers in diameter. This small core size allows only one mode of light to propagate through the fiber, which results in less modal dispersion and enables longer-distance signal transmission with higher bandwidth. In contrast, multimode fibers have a much larger core, usually around 50 to 62.5 micrometers, which accommodates multiple modes of light. While this design facilitates easier coupling of light into the fiber and is more forgiving regarding alignment, it leads to higher modal dispersion, limiting the distance over which the signal remains clear. Understanding the differences in core size is crucial for determining the appropriate type of fiber for specific applications, especially in environments that require high-speed data transmission over long distances. This knowledge helps in making informed decisions about fiber optic installations and troubleshooting potential issues related to performance.