The two most common core diameters in multi-mode fiber are ______.

The two most common core diameters in multi-mode fiber are ______.

• A. 25 microns and 50 microns
• B. 40 microns and 60 microns
• C. 50 microns and 62.5 microns
• D. 75 microns and 100 microns

Answer: (C)

Multimode fiber uses relatively large cores to support multiple light paths, and over time two core sizes became standard. The common core diameters are 50 microns and 62.5 microns, typically with 125 micron cladding (50/125 and 62.5/125). The 62.5 μm variant was popular with older LED sources because its larger core and higher numerical aperture made coupling easier and more forgiving of alignment. The 50 μm variant is now the workhorse for higher bandwidth over shorter distances, providing better modal dispersion performance with modern VCSEL/LED sources. Other core sizes exist, but 50 μm and 62.5 μm are the two you’ll see most often in multimode networks.

Multimode fiber uses relatively large cores to support multiple light paths, and over time two core sizes became standard. The common core diameters are 50 microns and 62.5 microns, typically with 125 micron cladding (50/125 and 62.5/125). The 62.5 μm variant was popular with older LED sources because its larger core and higher numerical aperture made coupling easier and more forgiving of alignment. The 50 μm variant is now the workhorse for higher bandwidth over shorter distances, providing better modal dispersion performance with modern VCSEL/LED sources. Other core sizes exist, but 50 μm and 62.5 μm are the two you’ll see most often in multimode networks.