Sorting through cables and connectivity options can be a frustrating exercise. That’s what this article is designed to help out with — how to select the right type of fiber optic cable.
Simplex vs. Duplex
Simplex vs. duplex is just the difference between one fiber or two; between one connector at each end of a cable, or two connectors at each end. That’s all there is to it. Duplex patch cords are the most common type, because the way that most fiber electronics work is that they need two fibers to communicate. One is used to transmit data signals, and the other receives them. However, in some instances, only one fiber is required, so simplex patch cords may be necessary for certain applications. If you’re not sure, you can always be on the safe side by ordering duplex patch cords, and only using one of the two fibers.
Multimode and Single mode
One of the first things to determine when choosing fiber optic cables is the “mode” of fiber that you need. The mode of a fiber cable describes how light beams travel on the inside of the fiber cables themselves. It’s important because the two modes aren’t compatible with each other — you can’t substitute one for the other.
There’s really not much variety with single mode patch cords, but there is for multimode. There are varieties described as OM1, OM2, and OM3. Basically, these varieties have different capabilities around speed, bandwidth, and distance, and the right type to use will depend mostly upon the hardware that is being used with them, and any other fiber that the patch cords will be connecting to.
Single Mode Fiber Optic Cable
Multimode Fiber Optic Cable
Let’s take a look at the common connector types:
LC — A Lucent connector (LC) is a connector with a 1.25 mm ferrule, half the size of an SC or ST connector.
SC — A 2.5 mm snap-in connector. SC connectors, as noted above, are larger than LC connectors. SC connectors are used with some styles of fiber optic extenders, although LC tends to be more common.
ST — This is a round connector that uses a bayonet-style mechanism that has to be twisted into place. It is about the same size as the SC connector. It was once the most popular connector type, but is losing ground rapidly.
Fiber optic patch cables will be used in a variety of installation environments, thus there will be requirements for the jacket materials. The standard jacket type is called OFNR (optical fiber non-conductive riser) which contains no metal in it, conduct stray electric current, and can be installed in a riser application (going from one floor up to the next, for instance). OFNR cable jacket is also known as plenum jackets, which are suitable for plenum environments such as drop-ceilings or raised floors. Many data centers and server rooms have requirements for plenum-rated cables. Another jacket type is LSZH (low-smoke zero-halogen), which is made from special compounds which gives off very little smoke and no toxic halogenic compounds when burned and is being used in many public places, like schools, hospitals, train stations, etc.
These are the most common selections that you’ll find when choosing among patch cords. If you’re able to determine which of these characteristics you need, it’s highly likely you will make the right choice when shopping for fiber optic patch cables.