Which type of fiber optic cable carries higher bandwidth over hundreds or thousands of kilometers and typically requires more expensive electronics to generate light?

• A. Single-mode cables
• B. Multimode cables
• C. Coaxial cables
• D. Twisted pair cables

Answer: (A)

Single-mode fiber carries higher bandwidth over long distances because its tiny core allows only a single light path, which dramatically reduces modal dispersion. When light travels through fiber, different paths can cause parts of the signal to arrive at different times; multimode fiber has many paths, so dispersion accumulates quickly and limits how much data can be sent reliably over hundreds or thousands of kilometers. With a single path, the signal stays together much longer, enabling much higher data rates over long distances. The light source in these systems is typically a laser diode operating at infrared wavelengths (like 1310 nm or 1550 nm), which is more expensive than the LEDs used with multimode fiber, hence the pricier electronics. Multimode fiber uses a larger core and supports many propagation paths, leading to more dispersion and lower usable bandwidth on long links, while copper options are not fiber and don’t offer the same long-distance high-bandwidth capabilities.