C-COR NA15T Series Procedures Manual - 2.0
MX0860
Revision B
Fiber Care and Cleaning
9
2.0
Fiber Care and Cleaning
The fiber optic medium does not suffer from problems associated with copper-based coaxial cables, such as
electromagnetic interference and increasing loss of signal power at higher frequencies and cable lengths.
However, the ability of the optical fiber, a thin, flexible strand of silica glass, to enable light to travel through
it with as little impedance as possible depends on the purity of the glass, the manner of its construction, and
its care during handling, splicing, and installation. The information in the following sections should be
considered before installation. Consult Recommended Practices for Optical Fiber Construction and Testing
published by the Society of Cable Telecommunications Engineers (SCTE) for further information.
2.1
Fiber Handling
Often fiber optic cable must be unreeled before installation. SCTE recommends the figure-eight method to
avoid twisting or bending. For shorter lengths of fiber cable (~2000 feet or 600 meters), remove the fiber cable
from the reel, and coil it on the ground into a figure-eight about 15 feet (4.5 meters) in length, with coils
5 feet (1.5 meters) in diameter. For longer lengths of fiber cable, coil the fiber cable into a figure-eight about
30 feet (9 meters) in length, with coils 10 feet (3 meters) in diameter. Use cardboard shims between sections
of fiber cable at the crossover locations of the figure-eight to relieve excess pressure.
Singlemode fiber, typically used in HFC architecture, is composed of an 8µm glass core, surrounded by
100-200µm of cladding, which protects the core and serves to bend the optical energy back into the core. The
cladding is protected by a 1 mm plastic buffer coating. To ensure that the integrity of the cladding and glass
core are maintained, proper handling of the fiber cable is required.
When installing fiber optic cables in ducts, on above-ground strands, or underground:
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do not exceed the fiber cable manufacturer’s maximum pulling tension
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do not exceed the fiber cable manufacturer’s minimum bending radius
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do not subject the fiber cable to crushing forces.
If cable specification documents are not available from the system manager, pulling tension should not exceed
600 pounds (~273 kg) during installation of non-connectorized fiber optic cable. The general minimum
bending radius for a fiber cable under tension is 20 times the diameter of the fiber cable. The general
minimum bending radius for a fiber cable not under tension—and in fiber management within a fiber optic
node—is 10 times the diameter of the fiber cable. When securing connectorized fiber leads within node
housings with cable ties, use caution to avoid crushing the plastic buffer or cladding.
Bare fibers are extremely sharp and can easily break. SCTE recommends wearing both
gloves and safety glasses while preparing fiber optic cable and also properly disposing
of broken optical fibers to avoid injury to the skin or eyes.
Use caution when handling fiber (for example, feeding fiber connectors through housing
ports and managing fiber within housings), to avoid a bend radius of less than 2 inches
(50 mm) in the fiber leads.
Caution
MX0860.fm Page 9 Wednesday, August 25, 1999 1:34 PM