Fiber with a core of roughly 8 to 9 µm inside 125 µm of cladding, small enough that only one mode propagates at the working wavelengths of 1310 and 1550 nm. With no modal dispersion to smear pulses, its bandwidth over distance far exceeds multimode, and cabled loss runs about 0.35 dB/km at 1310 nm and 0.25 dB/km at 1550 nm. It needs laser sources and tighter connector tolerances than multimode, but the fiber itself is the cheapest glass in the catalog.
Pull a 12-count of singlemode to every IDF next to the OM4, nobody ever regrets having the yellow cable in the tray.
Yellow jacket means singlemode on indoor cable, and blue connectors mean UPC singlemode, so a quick glance tells you which glass you are holding.
Also heard as
- SM
- SMF
- single-mode
- singlemode
Do not mix it up with
- Multimode fiber: Multimode has a 50 or 62.5 µm core that carries many light paths, which limits its reach to a few hundred meters at high data rates.
Related terms
Multimode fiber
Fiber with a 50 or 62.5 µm core that carries many light paths at once, used for short links inside buildings and data centers.
OS2
Optical Singlemode 2: the low-water-peak cabled singlemode grade used for most indoor and outdoor singlemode installs.
Mode field diameter
The effective width of the light spot traveling in a singlemode fiber, slightly larger than the physical core.
Core
The central glass region of an optical fiber where the light actually travels.
Window
A wavelength region where fiber loss is low enough to run links, such as 850, 1310 or 1550 nm.