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S T E V E P A U L O V

The main purpose for hardware is to protect and organize splice and termination
points. Hardware can be divided into two categories; indoor and outdoor. We
deal primarily with indoor hardware in this chapter, as applicable to commercial
buildings and campus environments, with a final review of outside plant hard-
ware at the end of the chapter.

Fiber optic cable plant design requires preplanning to select the proper hard-

ware. You need to know the number of fibers to pull to each location and the
purpose for each fiber. From there you can plan your hardware and the type of
cable to be used for riser, plenum, or other applications. You should also plan the
conduit, duct, and inner duct. The designer should decide in advance on the net-
works, support systems, and topologies to be used, such as Ethernet, token ring,
voice, data, video, imaging, control, and industrial applications. Once the appli-
cation is determined and the fiber and connection/splice is known, the route must
be determined. Then we can decide on locations for the hardware cabinets, racks,
and associated panels.

There are rules for fiber distribution established by the EIA/TIA 568 Commit-

tee. The EIA/TIA 568 Commercial Building Wiring standard is based on a hierar-
chical star for the backbone and a single star for horizontal distribution. Rules for
backbone wiring include a 2,000-meter (6,557-ft.) maximum distance between
the main cross-connect and the telecommunications closet, with a maximum of

97

Figure 7-1

Backbone cabling.

one intermediate cross-connect between the main cross-connect and the telecom-
munications closet (Figure 7-1) Many networks are installed in a simpler, less
expensive “homerun” design (Figure 7-2). The four main functions of each distri-
bution point (using the EIA/TIA 568 nomenclature) are as follows:

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CHAPTER 7 — FIBER OPTIC HARDWARE

500 m

(1,639

' )

90 m

(295

')

Horizontal Wiring

Telecommunications

Closet

Work Area

Telecommunications

Outlet

Intermediate

Cross-Connect

Main

Cross-Connect

2,000 m

(6,557

' )

Backbone Wiring

1,500 m

(4,918

' )

Figure 7-2

“Homerun” or centralized fiber cabling system.

CHAPTER 7 — FIBER OPTIC HARDWARE

99

1. Main cross-connect. The main cross-connect (MC), also referred to as

the main distribution frame (MDF), should be in proximity to or in the
same location as the data center or PBX. This placement ensures a cen-
tralized management point for reconfiguration of the fiber optic net-
work. Equipment in the MC should be capable of the following:

Handling adequately large fiber counts
Accepting either direct termination of equipment or pigtail splices and
preterminated assemblies for splicing at the frame
Providing jumper storage and reconfiguration capabilities
Allowing for growth

Typically, MC equipment can be installed in racks or wall cabinets.

2. Intermediate cross-connect. The intermediate cross-connect (IC) typi-

cally connects the intrabuilding cable plant to the interbuilding cable
plant. It is smaller in scope with lower fiber counts than the MC. Prod-
ucts in the IC may need to be wall mounted. The size of the IC will deter-
mine which products will be used.

3. Telecom closet hardware. Telecom closet (TC) equipment makes the

transition from the backbone to the horizontal cable plant.

4. Work area telecom outlet. The work area telecom outlet is the end point

of the horizontal wiring. The cables may be fiber only or a combination
of fiber and copper.

In each of the above distribution points, one or more of the following hardware
components can be installed.

1. Splice panel. The splice panel changes outside cable to riser or plenum

cable or breaks out the outside cable to individual buffered fibers. After
being spliced, the fibers are routed to the appropriate splice tray and
positioned to prevent damage. The splice panel may accommodate
fusion or mechanical splices and can be mounted in a rack or wall cabi-
net (Figure 7-3).

2. Patch panel. A patch panel provides a centralized location for patching

fibers, testing, monitoring, and restoring riser or trunk cables. Figure 7-4
shows an incoming riser cable being terminated on one side of a coupling
panel with a connector. On the other side of the coupling panel is
another group of connectors terminating the LAN cables. In small
offices, the patch panel can be used as an MC or IC. To order this type of
panel, you must know the type of connectors for the coupling panels, the
number of connections needed, the type of cabinet, whether the panel
will be wall or rack mounted, and the size of the cabinet required for the
number of panels to be installed.

3. Wall outlet. A wall outlet (Figure 7-5) terminates the permanent wiring

and provides a connection for a short jumper cable to connect the network

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101

Figure 7-3

Splice panels connect individual fibers from cables to

pigtails. Courtesy AMP

Figure 7-4

The patch panel makes connection between two cables.

Here we see single fiber jumpers connected to a breakout cable.
Courtesy 3M

equipment. Wall outlets can be wall mounted or permanently installed
into the wall surface.

4. Panels. When designing your cabinets, you can select the panel with the

type of coupling to fit the connectors you have chosen. You can also
order coupling panels without the couplers and install these yourself if
the type of connectors to be used will not be known until the cut-over
date.

Each manufacturer has a unique design for stacking equipment

panels. One such method involves stacking the panels on a relay rack.
Another method places the panels in a cabinet, and each cabinet is
installed on the wall above each other or side by side. When ordering any
cabinet make sure it is equipped with cable-terminating equipment such
as ground clamps, a place to secure the dielectric central member, Kevlar
or other fill material, and cable ring or channel guides.

5. Pigtail splicing. A fiber optic pigtail splice is a fiber cable that has been

factory connectorized on one end with an optical connector. The other
end remains unterminated. The unterminated end of the pigtail is spliced
to the fiber requiring termination. Pigtails are used almost exclusively for
singlemode applications but occasionally for multimode. Generally pig-
tails are bought as terminated jumpers and cut in half for splicing. That
way, they can be tested more easily to ensure the connectors are good
before splicing them onto the fibers.

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CHAPTER 7 — FIBER OPTIC HARDWARE

Figure 7-5

Wall outlets terminate cables

in convenient locations for desktop
connections. Courtesy AMP

6. Outside plant hardware. For cable runs outside, one generally is con-

cerned with splice closures (Figure 7-6), since connectors are used only at
the terminated ends inside buildings. Splice closures are available for
direct burial, use in controlled environment vaults (CEVs), aerial or
pedestal installation. Most closures are sealed once splices are loaded.
Closures must be chosen to be appropriate for the installation location
and splice trays must fit the type of splice to be used.

7. Conduit. Fiber optic cable is often installed in conduit (Figure 7-7). The

conduit can protect the cable from damage, water, or stress, both during
and after installation. Conduit comes in many types from simple corru-
gated innerduct to steel pipe. Due to the concern over damaging fiber
optic cable during installation, many types of conduit have been designed
to facilitate installing long lengths of cable without exceeding the cable
pull limits.

Even indoors, fiber is often installed in simple innerduct. This identifies the

cable as fiber and protects it from damage during the installation or removal of
other cables. It may also make installation faster, if the innerduct has preinstalled

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Figure 7-6

Outside plant splice closure for 3M Fiberlok mechanical splice.

Courtesy 3M

pulling tape. The duct can be installed by relatively unskilled personnel, the fiber
installed quickly without as much concern for damage, since it is protected by the
innerduct.

Outdoors, conduit and innerduct, along with proper lubrication, can extend

the pulling length considerably. They can be chosen from a number of styles and
sizes to fit the number and sizes of cables to be installed, especially considering
future expansion. Some manufacturers even offer conduit or innerduct with fiber
optic cable supplied to the customer’s specifications preinstalled and ready for
direct burial or pulling into preinstalled conduit.

Trenching for conduit: In paved areas, the surface should be carefully cut to

prevent unnecessarily excessive width at the top of the trench and thus reduce the
amount of surface to be repaved. For economical operation, particularly where
paving is involved, the trench width should be no greater than is needed to pro-
vide adequate working space. Generally, this dimension is controlled by the types
of excavating equipment used. As a minimum, the trench must be 4 inches wider
than the width of the conduit structure where backfill will be used, and 3 inches
wider where concrete encasement will be used. Individual job specifications will
dictate trench width. Grade and level the trench bed. Where necessary, provide

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CHAPTER 7 — FIBER OPTIC HARDWARE

Figure 7-7

Two fiber optic cables being pulled through innerduct that has

previously been pulled into conduit. Courtesy Condux

sand and/or other granular backfill as bedding material so the conduit will be
evenly supported over the length of each section.

In order to make optimum use of the conduit for subsequent cable placing

operations, particular care should be taken concerning direction changes. The
ideal duct structure is one that is essentially straight and allows for grading for
drainage into manholes. Direction changes should be made as gradual as possible.

When a road bore has to be made, the recommended procedure is to install a

pipe that is large enough for the joined sections of conduit to slide completely
through. In an instance where this is not possible and only a 4-inch steel pipe is
present for the bore, the innerduct can be used for insertion through the steel
pipe.

REVIEW QUESTIONS

1. ________________ provides a centralized management point for network

configuration.

a. Work area telecom outlet

b. Telecom closet

c. Intermediate cross-connect

d. Main cross-connect

2. ________________ make the transition from the backbone to the hori-

zontal cable plant.

a. Work area telecom outlet

b. Telecom closet

c. Intermediate cross-connect

d. Main cross-connect

3. The main purpose of hardware is to ________________

a. splice fibers.

b. protect and maintain fiber optic cable.

c. simplify pulling cable.

d. provide an airtight enclosure.

4. The ideal duct structure is ________________

a. indoors.

b. straight and allows for drainage.

c. color coded.

d. 4 inches wider than the conduit.

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