Structured Cabling System
Backbone Topology
Equipment room main cross-connect
Backbone cable
Telecommunications room
To work area via horizontal cable
Backbone cable
Equipment room intermediate cross-connect
Backbone cable
Telecommunications room
To work area via horizontal cable
Physical environment.
– EMI. Install copper away from areas of EMI.
– Physical plant systems. Install away from a building’s physical plant systems, such as electrical wiring, plumbing, and sprinklers.
Do not install backbone cable in elevator shafts.
– Environment. Air spaces should be examined for dampness, which can corrode copper cable.
In addition, take into account all pathway standards and requirements.
– Fire resistance. Pay attention to all fire regulations.
– Security. Make sure your backbone cable and all equipment and telecommunications rooms are inaccessible to unauthorized personnel. a central location called the main cross-connect. Each telecommunications room or equipment room is cabled to the main cross-connect either directly or via an intermediate cross-connect. A benefit of this topology is that it provides damage control. If a cable goes out, only that segment is involved. Others are unaffected.
Here are some backbone cabling recommendations:
• The backbone system shall be installed in a hierarchical star topology.
• From the horizontal cross-connect, there shall be no more than one additional cross-connect to reach the main cross-connect.
• There should be no more than two levels of backbone cross-connects.
• There shall be no bridged taps and splitters.
• Make sure you meet all grounding requirements.
Recognized media.
The cable you choose depends on your application and distance requirements. Fiber and copper cables have different characteristics that may make one more suitable for a particular application over the other. You may even use a combination of the two.
For instance, you can use fiber to connect runs between buildings and for the vertical riser within a building. But you may decide to use copper for the second level backbone connecting the intermediate cross-connects to the horizontal cross-connects.
Recognized cables include:
• 4-pair, 100-ohm twisted-pair cable
(TIA/EIA-568-B.2).
• 50- or 62.5-micron multimode fiber optic cable
(TIA/EIA-568-B.3).
• Single-mode fiber optic cable (TIA/EIA-568-B.3).
Backbone topology.
The recommended topology is a conventional hierarchical star where all the wiring radiates from
Media Type
100-ohm Copper
Multimode Fiber
Single-mode Fiber
Maximum distances.
Backbone cable distances depend on the application as well as the cable used. For allowed distances, see the chart below .
Backbone Cabling Distances
Main Cross-Connect to Main Cross-Connect to
Horizontal Cross-Connect Intermediate Cross-Connect
800 m (2624.7 ft.)
2000 m (6561.7 ft.)
3000 m (9842.5 ft.)
500 m (1640.4 ft.)
1700 m (5577.4 ft.)
2700 m (8858.3 ft.)
Intermediate Cross-Connect to Horizontal Cross-Connect
300 m (984.3 ft.)
300 m (984.3 ft.)
300 m (984.3 ft.)
20 Black Box Guide to Structured Cabling
