Certified Fiber Optics Practice Exam

Which type of fiber optic cable is typically used for long-distance communication?

1. Single-mode

2. Multimode

3. Ribbon

4. Drop

The correct answer is: Single-mode

Single-mode fiber optic cable is designed specifically for long-distance communication. This is due to its construction, which features a small core diameter (usually around 8 to 10 micrometers) that allows only one mode of light to propagate through the fiber. This single pathway minimizes modal dispersion, which occurs when multiple light modes travel at different speeds and can cause signal degradation over long distances. As a result of these characteristics, single-mode fibers are capable of transmitting data over much longer distances—often exceeding 50 miles (or 80 kilometers) without the need for signal repeaters—compared to multimode fibers, which are more suitable for shorter distances due to their larger core that allows multiple light paths and greater modal dispersion. The other options, such as multimode, ribbon, and drop cables, are designed for different applications. Multimode fibers are better for shorter runs within buildings or campus environments, ribbon cables are advantageous for high-density applications but still primarily fall within multimode or single-mode classifications, and drop cables are specifically designed for connecting individual users to a fiber network but are not tailored for long-distance communication like single-mode fibers.