Tight-buffered and loose-tube are two main fiber optic cable types in terms of different cable construction as we have mentioned in the previous post “loose-tube vs. Tight-buffered fiber optic cable”. Loose-tube cable is specially designed for harsh outdoor environments, while tight-buffered cable, in contrast, is optimized for indoor applications. However, with the the special design of armored layer, tight-buffered cable can be also applied for indoor/outdoor applications, which can be either distribution cable or breakout cable. In this post, I will introduce these two tight-buffered cable types, and simply compare them.
Distribution Fiber Optic Cable
Distribution fiber optic cable is often used as a direct equivalent of loose-tube gel-filled cable, because of its smaller size and capability to have a high fiber count. It contains several tight-buffered fibers bundled under the same jacket with Kevlar strength members as shown below and sometimes fiberglass rod reinforcement to stiffen the cable and to prevent kinking. Fiber distribution cable is usually designed with intensive fiber counts up to 144, many of which may not be used immediately, but should be considered for future expansion.
According to different rating, distribution cable has two types—distribution riser cable and distribution plenum cable for indoor/outdoor applications. Distribution plenum cable is usually used for trunking applications where fiber distribution cable is being run through environmental airflow spaces, while distribution riser cable is more available for vertical run. It can be armored for additional strength in direct burial and aerial applications.
Distribution fiber optic cable is ideal for applications requiring a single termination point with multiple fibers. It has a tight-buffered design, so it can be installed in intra-building backbone and inter-building campus locations without expensive transitions between cable types. Distribution cable usually ends up at patch panels or communication closets, where they are hooked into devices that communicate with separate offices or locations. However, because their fibers are not individual reinforced, distribution cable needs to be broken out with a “breakout box” or terminated inside a patch panel or junction box to protect individual fibers.
Unlike distribution cable, in which tight-buffered fibers are bundled together, with only the outer cable jacket of the cable protecting them, Breakout fiber optic cable or fanout fiber optic cable contains two or more simplex cables bundled around a central strength member, with each fiber having its own jacket and all of the fibers packaged together inside the same outer jacket as shown in the following image. The design of breakout cable adds strength for ruggedized drops, however the cable is larger and more expensive than distribution cable. The fiber counts in breakout cable are available in 2 to 48.
Like distribution cable, breakout cable also has the same two types—breakout plenum cable and breakout riser cable. Breakout plenum cable is available for ducts, plenums and other spaces with environmental air returns, while breakout riser cable is used when installing networking fiber optic cable from indoor to outdoor.
Breakout fiber optic cable is the ideal choice for installation where direct termination of fiber connector to sub-units and a direct run to fiber patch panels is desired. It is used for rugged applications where maximum physical and environmental protection is needed. The design of each fiber individually reinforced allows breakout cable for quick termination to connectors and not require patch panels or boxes. Breakout cable can be more economic where fiber count isn’t too large and distances too long, because it requires so much less labor to terminate.
Tight-buffered cable has gained much popularity with quick termination and low installation cost. Breakout and distribution cable are two common types of tight-buffered cable that we have discussed in the text above from the aspects of structure, cable type and application, which can help you to choose the right tight-buffered cable for your need.