Which type of fiber uses multiple light paths and typically has a core diameter in the 50–100 micron range?

• A. Multi-mode Fiber
• B. Single-mode Fiber
• C. Coaxial Cable
• D. Fiber Channel

Answer: (A)

Light traveling through fiber can take different routes depending on the size of the core. A larger core lets light reflect at many angles and follow multiple paths, which creates modal dispersion as signals arrive at slightly different times. That behavior is the hallmark of multi-mode fiber, and its core is typically in the 50–100 micron range. Because the multiple paths smear the signal over distance, multi-mode fiber is usually used for shorter, cheaper links. In contrast, single-mode fiber uses a much smaller core (about 8–10 microns), guiding light along essentially one path to minimize dispersion and enable long-distance transmission. Coaxial cable is copper-based, not fiber, and Fiber Channel refers to a storage networking protocol, not a fiber type.