Page 82 - Optical Communications Essentials

Optical Fiber Cables

72 Chapter Five

Figure 5.4. Example of a 12-fiber ribbon cable.

and effort are needed when attaching connectors or splicing fibers in gel-filled
cables. Each fiber must be individually cleaned to remove the gel, and the
breakout point of the main cable must be blocked by some method to prevent
the cable gel from oozing out of the jacket. This time-consuming and labor-
intensive process adds costs to the installation of loose-tube gel-filled cable.

5.2.3. Ribbon cable
To facilitate the field operation of splicing cables containing a large number of
fibers, cable designers devised the fiber-ribbon structure. As shown in Fig. 5.4,
the ribbon cable is an arrangement of fibers that are aligned precisely next to
each other and then encapsulated in a plastic buffer or jacket to form a long con-
tinuous ribbon. The number of fibers in a ribbon typically ranges from 4 to 12.
These ribbons then can be stacked on top of one another to form a densely
packed arrangement of many fibers (say, 144 fibers) within a cable structure.

5.3. Indoor Cables

Just as an interior decorator can think of innumerable ways to rearrange living
quarters, there are many different ways in which to arrange fibers inside a cable.
The particular arrangement of fibers and the cable design itself need to take into
account issues such as the physical environment, the services that the optical link
will provide, and any anticipated maintenance and repair that may be needed.

5.3.1. Indoor cable designs
Indoor cables can be used for interconnecting instruments, for distributing sig-
nals among office users, for connections to printers or servers, and for short
patch cords in telecommunication equipment racks. The three main types are
described here.

■ Interconnect cable. Interconnect cables are designed for light-duty low-fiber-
count indoor applications such as fiber-to-the-desk links, patch cords, and
point-to-point runs in conduits and trays. The cable is flexible, compact, and
lightweight with a tight-buffered construction. By using the simplex tight-
buffered unit shown in Fig. 5.2, a number of different indoor cable types can

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