What Are the Different Types of Optical Fiber Cable?

Alex Newth

There are many types of optical fiber cable used to supply data to mobile phones, computers and TVs, each handling light in a different way, and each made for a different application. The two main types of optical fiber cable are multi-mode and single-mode, which use either several beams of light or a single beam at once. Simplex cables use only one or two optical fibers and Kevlar® protection. Tightpack cables contain many optical fibers, but the fibers are not individually terminated. Loose-tube cables include a water-blocking gel and are used outside or are buried underground.

Some optical fiber cables are tightly packed, with many fibers encased in one cable.
Some optical fiber cables are tightly packed, with many fibers encased in one cable.

Multi-mode and single-mode are the two main types of optical fiber cable, though the terms do not refer so much to the cable design as to how the fibers interact with light. The multi-mode version sends out many different light beams at once, and each is sent at a different angle so the beams cannot interact with each other, eliminating the chance of interference. These types of optical fiber cable can only be used for short distances; otherwise, the light beams begin to interfere with on another. Single-mode optical fibers send only one beam of light at a time, making them ideal for long distances, because there are not multiple light beams to cause interference.

Tightpack cables are similar to simplex but include many more fibers.
Tightpack cables are similar to simplex but include many more fibers.

Simplex cables are simple fiber optic cables that are used for backplanes and patch-cord purposes. The outside is reinforced with Kevlar® to keep the optical fibers from wearing down as a result of outside stress. Inside, there are only one or two fibers, which make it good for applications for which limited energy is needed.

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Tightpack cables are similar to simplex but include many more fibers. The fibers are paired up and jacketed, as with the simplex cables, but there are many pairs, not just one. A major difference, aside from fiber number, is that the fibers are not individually terminated or protected, so there must be a termination unit connected to these types of optical fiber cable. These cables are used mostly for dry conduit runs over short distances.

Loose-tube cables do not use protection or jacketing for their internal fibers, but have another way of keeping the fibers safe. The insulation is filled with a water-blocking gel that is able to keep water from leaking into the cable and also keeps the fibers safe by adding durability to the inside of the cable. These cables are often used outside, either in the air or buried underground.

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