Which pair lists the two most commonly used multimode core sizes?

Which pair lists the two most commonly used multimode core sizes?

• A. 50um and 62.5um
• B. 25um and 50um
• C. 62.5um and 125um
• D. 50um and 125um

Answer: (A)

Multimode fiber carries multiple light paths, so the core diameter determines how many modes can propagate and how much modal dispersion you’ll have. The two core sizes you’ll see most in practice are 50 μm and 62.5 μm. The 62.5 μm size is the traditional standard that matched early LED sources and many campus networks. The 50 μm size is now the more common choice for higher-bandwidth links with VCSEL sources, because a smaller core reduces the number of modes and thus modal dispersion, enabling better performance at typical distances. That combination—50 μm and 62.5 μm—covers the vast majority of multimode deployments. Other options aren’t the two core sizes most used: 25 μm isn’t a standard pairing for the common multimode families, and 125 μm refers to the cladding diameter (not the core), so it doesn’t list the core sizes in question.

Multimode fiber carries multiple light paths, so the core diameter determines how many modes can propagate and how much modal dispersion you’ll have. The two core sizes you’ll see most in practice are 50 μm and 62.5 μm. The 62.5 μm size is the traditional standard that matched early LED sources and many campus networks. The 50 μm size is now the more common choice for higher-bandwidth links with VCSEL sources, because a smaller core reduces the number of modes and thus modal dispersion, enabling better performance at typical distances. That combination—50 μm and 62.5 μm—covers the vast majority of multimode deployments.

Other options aren’t the two core sizes most used: 25 μm isn’t a standard pairing for the common multimode families, and 125 μm refers to the cladding diameter (not the core), so it doesn’t list the core sizes in question.