Multimode fiber does not include single-fiber; it is a distinct type of fiber that allows multiple light modes to propagate simultaneously.

Multimode fiber (MMF) is designed with a larger core diameter, typically 50 µm or 62.5 µm, which enables multiple light paths or modes to travel through the fiber at the same time, making it suitable for short-distance, high-capacity data transmission within buildings or data centers . In contrast, single-mode fiber (SMF) has a much smaller core, around 8–10 µm, allowing only one mode of light to propagate, which minimizes signal loss and supports long-distance communication . The distinction is fundamental: multimode fiber cannot function as single-mode fiber, because the larger core inherently supports multiple light paths, leading to modal dispersion that limits distance and bandwidth compared to single-mode fiber . Both fiber types share the same cladding diameter of 125 µm, but their core sizes and light propagation characteristics define their separate applications . In summary, multimode fiber is a separate category from single-mode fiber and does not include single-fiber characteristics. Choosing between them depends on the required transmission distance, bandwidth, and network design considerations .