9/125 fiber optic cables are typical type single mode fiber cables. It is widely used in outdoor cables that are usually used as backbones in the fiber optic network, and it also is used in indoor cables like patch cord assemblies. Here the measurement unit of the 9 and 125 is μm (micron), one meter is equal to one million micron. So you can imagine how small the 9/125 optical fiber is, it is much smaller in diameter than human hair.

As you may have noticed, outdoor 9/125 single mode fiber cables is rather big diameter, while the indoor 9/125 singlemode fiber is smaller diameter, but they are both 9/125 type cables. Here we would like to give a picture to illustrate what the “9” and “125” means.

Above picture is a simple model of the commonly used 9/125 single mode fiber cable. We can see there are three layers of the cable. The 9 micron part refer to the center layer of  the optical fiber, its diameter is 9micron. The 125 part is center layer together with the cladding layer; their total diameter is 125micron. Then there are other materials like strength unit surround them,and then the jacket of the cable. you can understand easily why different out shape cables can all be with 9/125 single mode fibers.