Which part of the fiber optic cable is smaller in singlemode fiber compared to multimode fiber?

In singlemode fiber optic cables, the core is smaller than in multimode fiber cables. Singlemode fibers are designed to carry light signals over long distances with minimal modal dispersion, which is achieved with a smaller core diameter—typically around 8 to 10 microns. This smaller core allows only one mode of light to propagate, ensuring that the signal remains clear and consistent over the distance.

In contrast, multimode fibers have a larger core diameter, usually around 50 or 62.5 microns, allowing multiple modes of light to propagate simultaneously. While this can enable higher light carrying capacity over shorter distances, it also introduces modal dispersion where light paths travel at different speeds, potentially distorting the signal over longer distances.

The other components of the fiber optic cable, such as the primary buffer coating, cladding, and outer sheath, serve different functions but do not have the same size differential as the core in singlemode versus multimode fibers. The cladding diameter remains uniform in both types of fibers to maintain the necessary optical properties for guiding the light, while the buffer coating and outer sheath sizes can vary but are not primarily defined by the mode type of the fiber.