10.4.2.1 Cable Structures. In general, the same types of sheathing used
with copper-based systems can be used with glass-based systems. The systems
may include aerial cables, submerged cables, rodent-resistant cables, and
other types of cables. There is a lack of standardization in the area of
cable sheath design, but as the technology matures, standardization
undoubtedly will take place.
Cable Selection. The most important mechanical features to
consider in selecting a cable are as follows:
a) Tensile strength;
b) Adequate strength-member selection;
d) Support requirements;
e) Environmental specifications;
f) Length of continuous run available;
g) Lengths that can be safely pulled in conduits and raceways;
h) Probability of fiber breakage;
i) Compression strength.
Cables designed to contain electrical conductors and optical fibers
are also feasible and generally available. For example, twisted-pair wires
can be included for signaling applications, or to carry electrical power to
optical repeaters along the cable route.
10.4.2.3 Optical Connectors. The method used for splicing lengths of fiber
to each other and to terminating the ends in the appropriate connectors is an
important part of the optical link. Both fiber splices and cable terminations
can cause significant power losses and add to the complexity and cost of the
installation. The lack of standardization is also a problem in the technology
of optical connectors. In general, it can be assumed that a good fiber optic
connector will not have an attenuation greater than 1.5 dB. This number is
typical, but should be updated to the current state of the art at the time of
installation. The associated cable strength-member tie-off and sheathing
termination is characteristic of the cable type and is not different from
similar copper-based cables.
10.4.2.4 Fiber Splices. Optical fibers can be spliced in two ways: by
fusion and by an adhesive index-matching material. These two techniques
typically exhibit equal losses, varying from 0.1 to 0.5 dB optical
attenuation; however, in the current state of the art, the optical quality of
the index-matching adhesive (usually an epoxy) may deteriorate with time.
Fusion, on the other hand, is performed by melting the optical fibers together
into one mechanically and optically continuous fiber. Tool kits are readily
available to implement either of these techniques.