Airstream Gate 5 Fiber Optic Practice Test

Which description matches the typical core diameter and numerical aperture for single-mode fiber?

Core 50–62 μm, NA 0.20–0.275

Core 8–10 μm, NA 0.13–0.17

Single-mode fiber is defined by a very small core and a modest numerical aperture. The core is about 8–10 μm in diameter, and the numerical aperture is typically around 0.13–0.17. This combination lets only the fundamental light mode propagate, which reduces modal dispersion and supports high-bandwidth, long-distance transmission.

That matched description—core about 8–10 μm with NA around 0.13–0.17—fits single-mode fiber best. The other descriptions describe either much larger cores typical of multimode fiber or a small core with a relatively high NA that isn’t characteristic of standard single-mode fiber.

Core 8–10 μm, NA 0.25–0.40

Core 50–62 μm, NA 0.10–0.12