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OPTICAL CABLES
Optical fibers have small cross sectional areas. Without protection, optical fibers are
fragile and can be broken. The optical cable structure protects optical fibers from
environmental damage. Cable structure includes buffers, strength members, and jackets.
Many factors influence the design of fiber optic cables. The cable design relates to the
cable's intended application.
Properly designed optical cables perform the following functions:
Protect optical fibers from damage and breakage during installation and over the fiber's
lifetime.
Provide stable fiber transmission characteristics compared with uncabled fibers. Stable
transmission includes stable operation in extreme climate conditions.
Maintain the physical integrity of the optical fiber by reducing the mechanical stresses
placed on the fiber during installation and use. Static fatigue caused by tension,
torsion, compression, and bending can reduce the lifetime of an optical fiber.
Navy applications require that fiber optic cables meet stringent design specifications.
Fiber optic cables must be rugged to meet the optical, environmental, and mechanical
performance requirements imposed by Navy systems. Critical system downtime caused by cable
failure cannot be tolerated. However, in commercial applications, the requirements imposed
on cable designs are not as stringent.
Each additional requirement imposed on the fiber optic cable design adds to its cost.
Cost is always a main consideration of cable designers in commercial applications. Cost is
also considered in Navy applications, but system reliability is the main goal.
Q.26 List three benefits that properly cabled optical fibers provide.
FIBER BUFFERS
Coatings and buffers protect the optical fiber from breakage and loss caused by
microbends. During the fiber drawing process, the addition of a primary coating protects
the bare glass from abrasions and other surface contaminants. For additional protection,
manufacturers add a layer of buffer material. The buffer material provides additional
mechanical protection for the fiber and helps preserve the fiber's inherent strength.
Manufacturers use a variety of techniques to buffer optical fibers.
The types of fiber buffers include tight-buffered, loose-tube, and gel-filled
loose-tube. Figure 3-13 shows each type of fiber buffer. The choice of buffering
techniques depends on the intended application.
In large fiber count commercial applications, manufacturers use the loose-tube buffers.
In commercial building and Navy applications, manufacturers use tight buffers.
Figure 3-13. - Tight-buffered, loose-tube, and gel-filled loose-tube buffer techniques.
Q.27 In addition to a primary coating, manufacturers add a layer of buffer material for
what reasons?
Q.28 List the three techniques used by manufacturers to buffer optical fibers.
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