BACKBONE SUBSYSTEM

CABLING SYSTEM

Backbone Subsystem

• The Backbone cabling subsystem is based on cabling segments, which link such connection centers as Main Cross-Connect, Intermediate Cross-connects, and Horizontal Cross-connects.In these centers Backbone subsystem links are connected with each other thereby forming Backbone subsystem channels that are used to distribute telecommunications services (voice, data, image, etc) to the Horizontal cabling subsystem

• Backbone cabling subsystem also includes cabling between buildings

Backbone Subsystem

• The Backbone cabling subsystem consists of the following elements:

– Main Cross-connect (MC)

– Intermediate Cross-connect(s) (IC)

– Horizontal Cross-connect(s) (HC)

– Level I Backbone subsystem connecting MC with IC(s) or with HC(s)

– Level II Backbone subsystem connecting IC(s) with HC(s)

– Backbone cabling segments connecting Entrance Facility (EF) with MC or with IC(s)

– Patch cords connecting the segments of the Backbone subsystem in the MC and IC(s)

Backbone SubsystemLevel II

BackboneCabling

Subsystem

EF

HC

MCIC

HC

HC

HCIC

HC

EF

HC

ICHC

HC

EF

HorizontalCabling

Subsystem

Level IBackbone Cabling

Subsystem

HC - Horizontal Cross-connect

IC - Intermediate Cross-connect

MC - Main Cross-connect

EF - Entrance Facility

Building 1 Building 2

Building 3

Topology

• The Backbone cabling subsystem has a star topology with two hierarchy levels

• Each IC is connected with the MC by means of Level I Backbone subsystem. All links come together in the MC, thereby forming a star. This is the first level of the hierarchy.

• Each HC in its turn is linked with the IC by the Level II Backbone subsystem also forming a star with a single center in the MC. This is the second level of the hierarchy

Cross- and Interconnection

• In the Main Cross-connect and Intermediate Cross-connects two methods of connecting active equipment to the Backbone cabling subsystem and one method for passive connection between cable segments of the Backbone cabling subsystem are used

• More details on cross- and interconnection methods are given in “HORIZONTAL SUBSYSTEM” section

Design Rules

• The Backbone cabling subsystem can have only one MC

HC MC/IC

EF/ER/TR

HC

TR

Public Telecommunications Network

Campus Backbone Cabling System

HC

TR

HC

TR

TO WA

TO WA

TO WA

TO WA

Design Rules

• All HCs are connected with the MC directly or via ICs

TO

TO TO HC

HC

HC

IC

HC

HC

HC

HC

HC

TO TO

TO

MC

IC/HC

Design

• When choosing a layout and designing Backbone cabling subsystem the following factors should be taken into consideration:

– The backbone cabling is expected to serve the needs of building occupants for one or several planning periods, each period spanning three to ten years

– During each planning period, the backbone cabling design should accommodate growth and changes in service requirements without the installation of additional cabling.The length of the planning period should be based upon the stability and growth of the end user organization

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Design

– It is generally not possible or economically viable to install backbone cabling for the entire life of the generic cabling system

Instead the design may be based on current or foreseeable application requirements

Such short-term selection criteria is often appropriate for building backbone cabling where there is good physical access to pathways

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Design

– The selection of campus backbone cabling may require a longer term approach than that adopted for the building backbone, particularly if access to pathways is more limited

This limitation shall be taken into consideration when choosing inter-building Backbone cabling subsystem planning period (usually, longer planning periods are used)

– Each recognized cable has individual characteristics that make it useful in a variety of situations

A single cable type may not satisfy all end user requirements.The campus backbone cabling should contain the mix of cabling media and cable types necessary to support the desired applications

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Design

– When future service requirements are not well defined, use "worst case" scenarios when evaluating different backbone cabling alternatives

The higher the uncertainty, the more flexible the backbone cabling system needs to be

– When designing Backbone subsystem pathways and cross-connects special attention should be paid to relative position of EMI sources to the telecommunications cabling

Transmission Media

• The following types of transmission media are allowed in the Backbone cabling subsystem of the Signamax Cabling System:

– category 5e, 6, and 6a four-pair 100-Ohm unscreened cables

– category 5e, 6, and 6a four-pair 100-Ohm screened cables

– category 3 and 5 multipair 100-Ohm unscreened cables

– category 3 and 5 multipair 100-Ohm screened cables

– 50/125 µm optical fiber multimode cables

– 62.5/125 µm optical fiber multimode cables

– 9/125 µm optical fiber singlemode cables

Distances

• The maximum supportable distances in the Backbone cabling subsystem are application and media dependent

Specific applications may exist, or become available inthe future, that do not operate over the maximum distances specified for the Backbone cabling subsystem

• The Signamax Cabling System designers are advised to consult the specific standards associated with the planned service, or equipment manufacturers and systems integrators to determine the suitability of the cabling for specific applications

Distances

11 Maximum allowable distances in the Backbone cabling subsystem of the Signamax Cabling System shall be limited by the specifications of anticipated telecommunications applications, provided the cabling system stays within the boundaries of the end-user premises.

Category 5e, 6, and 6A twisted-pair transmission media between MC and HC, IC and HC, or MC and IC if the Backbone cabling subsystem is meant to support high data rate applications (with operation frequency range over 1 MHz) shall be limited by 100 m (328 ft).

Cord Length

12 Total length of category 5e, 6, or 6A twisted-pair equipment and patch cords in MC, IC, or HC shall be limited by 5 m (16 ft) in one Cross-connect and 10 m (33 ft) in both, if the Backbone cabling subsystem is meant to support high-speed applications (with operation frequency range over 1 MHz)

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Cord Length

12 Total length of twisted-pair equipment and patch cords in MC, IC, or HC shall be limited by the distance specifications of anticipated telecommunications applications taking into account 0.2 length de-rating factor for 24-AWG cables and 0.5 length de-rating factor for 26-AWG cables if the Backbone cabling subsystem is meant to support low-speed applications (with operation frequency range up to 1 MHz)

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Cord Length

12 Total length of optical fiber equipment and patch cords in MC, IC, or HC shall be limited by the distance specifications of anticipated telecommunications applications

Cord Length

5To enable convenient connection of active equipment and increase flexibility, in the Backbone cabling subsystem aimed to support high-speed applications (with operation frequency range over 1 MHz), the total length of equipment and patch cords in Cross-connects may be increased up to

• 25 m (82 ft) for 24-AWG cords

• 20 m (66 ft) for 26-AWG cords,

if the fixed cable length is not more than 70 m (230 ft)

TELECOMMUNICATIONSPATHWAYS AND SPACES

Pathways and Spaces

• Backbone pathways consist of intra- and interbuilding pathways

• Backbone pathways may be either vertical or horizontal

• Interbuilding backbone pathways extend between buildings

• Intrabuilding backbone pathways are contained within a building

Pathways and Spaces

• One or more backbone facilities may exist within a building

• A backbone facility is generally formed by vertically stacking teecommunications closets with floor openings between them

• Tie pathways may also exist to install backbone media between telecommunications closets on the same floor

Pathways and Spaces

• Intra-building Backbone pathways encompass:

– Underfloor pathways

– Access floor

– Conduit

– Tray and wireway

– Ceiling pathways

– Perimeter pathways

– Furniture pathways

Pathways and Spaces

• Inter-building Backbone pathways encompass :

– Underground

– Tunnels

– Aerial

Pathways and Spaces

16 All pathways where the Backbone subsystem cables are installed shall be intended for this purpose and shall not share their space with other services ofthe building

17 The Backbone distribution system pathways shall be designed and installed in compliance with local and federal construction regulations and electrical safety codes

Pathways and Spaces

22 All rules given in subsection “Telecommunications pathways and spaces” of section “HORIZONTAL SUBSYSTEM” of this Manual and the ones relating to design and installation of telecommunication distribution systems shall be followed for Backbone cabling subsystem