Definition - What does Single-Mode Fiber mean?
Single-mode fiber features only one transmission mode. Compared with multi-mode fiber, it can carry higher bandwidths; however, it needs to have a light source having a narrow spectral width.
Single-mode fiber is also known as a single-mode optical fiber, uni-mode fiber, mono-mode optical fiber and single-mode optical waveguide.
Techopedia explains Single-Mode Fiber
The optical fiber itself includes three fundamental parts: the core, the cladding and the coating or buffer. The most central part of the optical fiber is the core. This is the place through which the light travels. The core of single-mode fiber is much smaller than that of multi-mode fiber. There are three fundamental diameter sizes for fiber cores.
Single-mode fiber features a core diameter of nominally 9 µm, whereas multi-mode fiber often features a 62.5-µm or 50-µm core diameter. The small core, coupled with a single light wave, eradicates any distortion caused by overlapping light pulses, offering a minimal signal attenuation plus the highest transmission speed.
In contrast, multi-mode fiber provides users with high bandwidth at high speeds across moderate distances.
It is not advisable to mix and match fibers. If you try to connect a single-mode fiber with a multi-mode fiber, it may result in a 20-dB loss, which is 99% of the total power.