Multimode fiber is not a type of multi-core fiber; it is a single-core fiber that supports multiple light propagation modes.

Core Structure and Light Propagation

Multimode fiber (MMF) has a single, relatively large core—typically 50 to 100 micrometers in diameter—that allows multiple modes of light to propagate simultaneously through the same core . This is different from multi-core fiber, which contains multiple separate cores within a single cladding, each capable of carrying its own light signal independently. The large core of multimode fiber simplifies coupling with light sources like LEDs or VCSELs and is ideal for short-distance communication, such as within buildings or data centers [4^].

Modal Dispersion and Distance Limitations

Because multiple light modes travel at slightly different speeds in a multimode fiber, modal dispersion occurs, which limits the maximum transmission distance to a few hundred meters for high-speed data . Multi-core fibers, by contrast, can increase total data capacity without relying on multiple modes in a single core, reducing modal dispersion issues.

Applications

Multimode fibers are widely used for short-range, high-bandwidth applications, including enterprise networks, data centers, and backbone connections within buildings . Multi-core fibers are more specialized and are often used in high-capacity long-haul networks or research applications where space-division multiplexing is required.

Summary

• Multimode fiber: Single-core, multiple light modes, short-distance, cost-effective, easier to connect.
• Multi-core fiber: Multiple cores, each carrying light independently, higher capacity, used for advanced or long-distance applications. In conclusion, while multimode fiber supports multiple light paths, it remains a single-core fiber and should not be confused with multi-core fiber, which physically contains multiple cores within the same cladding .