A structured cabling system is a
complete system of cabling and associated hardware, which provides a
comprehensive telecommunications infrastructure. This infrastructure serves a wide
range of uses, such as to provide telephone service or transmit data through a
computer network. It should not be device dependent.
We further define a structured
cabling system in terms of ownership. The structured cabling system begins at
the point where the service provider (SP) terminates. This point is the point
of demarcation (demark) or Network Interface Device (NID).
For example, in a telephone system
installation, the SP furnishes one or more service lines (per customer
requirements). The SP connects the service line at the point of demarcation.
Every structured cabling system is
unique. This is due to variations in:
- The architectural structure of the building, which
houses the cabling installation
- The cable and connections products
- The function of the cabling installation
- The types of equipment the cabling installation will
support – present and future
- The configuration of an already installed system
(upgrades and retrofits)
- Customer requirement
- Manufacturers warranties
The methods we use to complete and
maintain cabling installations are relatively standard. The standardization of
these installations is necessary because of the need to ensure acceptable
system performance from increasingly complex arrangements.
The U.S. cabling industry accepts
the American National Standards Institute (ANSI), in conjunction with TIA/EIA,
as the responsible organization for providing and maintaining standards and
practices within the profession. It has published a series of standards to
design, install, and maintain cabling installations. These help to ensure
proper cabling installation.
The benefit of these standards
include:
- Consistency of design and installation
- Conformance to physical and transmission line
requirements
- A basis for examining a proposed system expansion and
other changes
- Uniform documentation
The industry standard term for a
network installation that serves a relatively small area (such a structured
cabling installation serving a building) is a local area network (LAN). There
are also metropolitan area networks (MANs) and wide area networks (WANs).
Structured cabling installations
typically include: entrance facilities; vertical and horizontal backbone
pathways; vertical and horizontal backbone cables; horizontal pathways;
horizontal cables; work area outlets; equipment rooms; telecommunications
closets; cross-connect facilities; multi-user telecommunications outlet
assemblies (MUTOA); transition points; and consolidated points.
The entrance facility includes the
cablings components needed to provide a means to connect the outside service
facilities to the premises cabling. This can include service entrance pathways,
cables, connecting hardware, circuit protection devices, and transition
hardware.
An entrance facility houses the
transition outside plant cabling to cabling approved for intrabuilding
construction. This usually involves transition to fire-rated cable. The
entrance facility is also the network demarc between the SP and customer
premises cabling (if required). National and regional electrical codes govern
placement of electrical protection devices at this point.
The location of the entrance
facility depends on the type of facility, route of the outside plant cabling
(e.g. buried or aerial), building architecture, and aesthetic considerations.
The four principle types of entrance facilities include underground, tunnel,
buried, and aerial.
In an aerial entrance, the SP cables
provide service to a building via an overhead route. Aerial entrances usually
provide the lowest installation cost, and they’re readily accessible for
maintenance. However, they’re subject to traffic and pedestrian clearances, can
damage a building’s exterior, are susceptible to environmental conditions (such
as wind and ice), and are usually joint-use installations with the power
company, CATV company, and telephone or data service providers.
Backbone cabling. From the entrance facility, the structured cabling network
branches out to the other buildings, as well as from floor to floor within a
building on the backbone cabling system. We use the term backbone to describe
the cables handling the major network traffic.
The ANSI/TIA/EIA-568-A standard
defines backbone cabling as follows: “The function of the backbone cabling is
to provide interconnections between telecommunications closets, equipment
rooms, and entrance facilities in the telecommunications cabling system
structure. Backbone cabling consist of the backbone cables, intermediate and
main cross-connects, mechanical terminations, and patch cords or jumpers used for
backbone-to-backbone cross-connection. Backbone cabling also includes cabling
between buildings.”
Interbuilding and intrabuilding are
two types of backbone cables. Interbuilding backbone cable handles traffic
between buildings. Intrabuilding backbone cable handles traffic between closets
in a single building.
This standard identifies two levels
of backbone cabling. First-level backbone is a cable between a main
cross-connect (MC) and intermediate cross-connect (IC) or horizontal
cross-connect (HC). Second-level backbone exists between an IC and HC.
The main components of backbone
cabling are:
- Cable pathways: shafts, conduits, raceways, and floor
penetrations (such as sleeves or slots) that provide routing space for the
cables
- The actual cables: optical fiber, twisted-pair copper,
coaxial copper, or some combination of these. (Note: You should avoid
areas where potential sources of EMI or electromagnetic interference may
exist when planning the routing and support structure for copper cabling.)
- Connecting hardware: connecting blocks, patch panels,
interconnections, cross-connections, or some combination of these
components
- Miscellaneous support facilities: cable support
hardware, firestopping and grounding hardware. Note: The terms horizontal
and backbone (previously called riser) evolved from the orientations
typical for functional cables of these types. However, the physical
orientation of the cabling has no bearing on classifying the cabling as
horizontal or backbone.
The useful life of a backbone
cabling system consists of several planned growth periods (typically 3 to 10
years). This is shorter than the life expectancy of the premises cabling
system.
Cabling connectors. A connector is a mechanical device you use to interface a
cable to a piece of equipment or one cable to another. The role of the
connector is to provide a coupling mechanism that keeps loss to a minimum.
In the case of fiber, it allows
light impulses to transfer from one connector to another. For copper, it allows
electrical signals to transfer from one connector to another.
A good connection requires aligning
the connectors, preventing the connectors from unintentional separation, and
efficient transferring of light or electricity from one connector to the other.
A connector demonstrates durability
by withstanding hundreds of insertion and withdrawal cycles without failing. We
calculate this as mean time between failures (MTBF).
Connectors are as essential to the
integrity of the entire telecommunications network as is the cable itself. Connectors
align, attach, and decouple the media to a transmitter, receiver, another media
of same or similar type, an active telecommunications device, or a specified
passive telecommunications device.
Contact MCC today for help
with your structured cabling needs!
For more details please contact us at:
Memphis Communications Corporation
4771 Summer Ave
Memphis, TN 38122
Tel: 901.725.9271
Fax: 901.272.3577
Toll Free: 866.805.5893
Service and Supplies: 901.257.2500
