Page 80 - Optical Communications Essentials

Optical Fiber Cables

70 Chapter Five

TABLE 5.1. Optical Cable Jacketing Materials and Their Applications
Jacket material Material properties
Polyvinyl chloride (PVC) Flame-retardant; good mechanical protection and flexibility. Widely
used for indoor cables. Used outdoors with UV light inhibitors
added
Polyethylene (PE) Excellent resistance to UV light, water, abrasion, and scrapes.
Excellent low-temperature flexibility. Since it burns, it is not
suitable for indoor use
Flame-retardant Adding a flame-retardant to PE results in a durable, highly
polyethylene (FRPE) abrasion-resistant jacketing. Widely used for indoor and outdoor
cables
Polyurethane (PU) Excellent resistance to abrasion, resistant to UV light, and flexible
at extremely low temperatures because of its natural pliability.
Widely used for military field communication cables and outdoor
deployable cables
ETFE (Tefzel) Resistant to high temperatures (150°C), abrasion, and flames. Stiffer
and more expensive than PVC so used only where its properties
are required
Low-smoke zero-halogen Will not emit toxic fumes, smoke, or acidic gases in case of a fire.
polyolefin Has mechanical performance comparable to that of a PVC or
FRPE jacket
Cross-linked polyolefin This material is widely used for highly demanding indoor/outdoor
applications due to its high resistance to abrasion, cuts, solvents,
ozone, and stress cracking

are used indoors whereas the loose-tube structure is intended for long-haul out-
door applications. A ribbon cable is an extension of the tight-buffered cable. In
all cases the fibers themselves consist of the normally manufactured glass core
and cladding which are surrounded by a protective 250-µm-diameter coating.
Let’s take a closer look at these structures.

5.2.1. Tight-buffered fiber cable
As shown in Fig. 5.2 for a simplex one-fiber cable, in the tight-buffered design
each fiber is individually encapsulated within its own 900-µm-diameter plastic
buffer structure, hence the designation tight-buffered design. The 900-µm
buffer is nearly 4 times the diameter and 5 times the thickness of the 250-µm
protective coating material. This construction feature contributes to the excellent
moisture and temperature performance of tight-buffered cables and also permits
their direct termination with connectors. The one-fiber cable shown in Fig. 5.2
is for light-duty indoor applications such as patch cords and local-area net-
works, or it can be used as a modular building block to create larger cables.
Surrounding the 900-µm fiber structure is a layer of aramid strength material
which in turn is encapsulated in a PVC outer jacket. A typical outer diameter
might be 2.4mm. Compared to other cable designs, tight-buffered structures

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