In telecommunication, the term outside plant has the following meanings:
In civilian telecommunications, outside plant refers to all of the physical
cabling and supporting infrastructure, and any associated hardware located
between a demarcation point in a switching facility and a demarcation
point in another switching center or customer premises.
In the United States, the DOD defines outside plant as the communications
equipment located between a main distribution frame and a user end
instrument. The CATV industry divides its fixed
assets between head end or inside plant, and outside plant. The electrical power
industry also uses the term outside plant to refer to electric power
distribution systems. Context
Network connections between devices such as computers, printers, and phones
require a physical infrastructure to carry and process signals. Typically,
this infrastructure will consist of: Cables from wall outlets and jacks run
to a communications closets, sometimes referred to as station cable.
Cables connecting one communications closet to another, sometimes referred to
as riser cable. Racks containing telecommunications
hardware, such as switches, routers, and repeaters.
Cables connecting one building to another.
Exterior communications cabinets containing hardware outside of
buildings. Radio transceivers used inside or
outside buildings, such as wireless access points, and hardware associated
with them, such as antennas and towers. The portion of this infrastructure
contained within a building is the inside plant, and the portion of this
infrastructure connecting buildings or facilities is the outside plant. Where
these two plants meet in a given structure is the demarcation point.
Outside plant cabling, whether copper or fiber, is generally installed as aerial
cable between poles, in an underground conduit system, or by direct burial.
Hardware associated with the outside plant must be either protected from the
elements or constructed with materials suitable for exposure to the elements.
Installation of the outside plant elements often require construction of
significant physical infrastructure, such as underground vaults. In older
large installations, cabling is sometimes protected by air pressure
systems designed to prevent water infiltration. While this is not a modern
approach, the cost of replacement of the older cabling with sealed cabling is
often prohibitively expensive. The cabling used in the outside plant must
also be protected from electrical disturbances caused by lightning or
voltage surges due to electrical shorts or induction.
Example: copper access network In civilian telecommunications, the
copper access network providing basic telephone or DSL services typically
consists of the following elements: In-house wiring that connects customer
premises equipment to the demarcation point, usually in residential
installations contained in a weather protected box.
One or more twisted pairs, called a drop wire. The drop wires typically connect
to a splice case, located in line for aerial cables, or in a small weather
protected case for underground wiring, where the local cabling is connected to
a secondary feeder line. These cables contain fifty or more twisted pairs.
Secondary feeder lines run to a streetside cabinet containing a
distribution frame called a Serving Area Interface.
The SAI is connected to the main distribution frame, located at a
Telephone exchange or other switching facility, by one or more primary feeder
lines which contain hundreds of copper twisted pairs. An SAI may also contain a
Digital subscriber line access multiplexer supporting DSL service.
Active equipment can then be connected to the line in order to provide service,
but this is not considered part of outside plant.
Protecting equipment in the outside plant
The environment can play a large role in the quality and lifespan of equipment
used in the outside plant. It is critical that environmental testing
criteria as well as design and performance requirements be defined for
this type of equipment. There are generally four operating
environments or classes covering all outside plant applications, including
wireless facilities. Class 1: Equipment in a Controlled
Environment Class 2: Protected Equipment in Outside
Environments Class 3: Protected Equipment in Severe
Outside Environments Class 4: Products in an Unprotected
Environment Electronic equipment located in one or
more of these environmental class locations is designed to withstand
various environmental operating conditions resulting from climatic
conditions that may include rain, snow, sleet, high winds, ice, salt spray, and
sand storms. Since outside temperatures can possibly range from −40°C to 46°C,
with varying degrees of solar loading, along with humidity levels ranging from
below 10% up to 100%, significant environmental stresses within the
enclosure or facility can be produced. Telcordia GR-3108, Generic Requirements
for Network Equipment in the Outside Plant, contains the most recent industry
data regarding each Class described above. It also discusses what is
currently happening in ATIS and Underwriters Laboratories.
The document also includes Environmental criteria such as operating
temperatures, humidity, particulate contamination, pollution exposure, and
heat dissipation Mechanical criteria such as structural
requirements, packaging, susceptibility to vibration, earthquake, and handling
Electrical protection and safety including protection from lightning
surges, AC power induction and faults, and Electromagnetic Interference, and DC
power influences = Handholes and other below-ground
splice vaults = Handholes and other below-ground splice
vaults house telecommunications components used in an Outside Plant
environment. Handholes are plastic or polymer
concrete structures set below ground with their lids flush to the surrounding
soil, turf, footpath, or road surface. They can be used to house and protect
copper, coaxial, and optical fiber telephone cable splices and distribution
elements. They safeguard and provide convenient access to cable termination
and branch points, provide flexibility and access for installation operations,
provide mechanical and environmental protection for splices, allow access for
craftsperson work activities, and discourage access by unauthorized
persons. Handholes and other below-ground splice
vaults are deployed in a variety of environments. The major distinctions in
these environments focus on the strength and frequency of vehicular and foot
traffic loading. There are four basic application environments:
Light Duty: Pedestrian Only Medium Duty: Pedestrian and Light
Incidental Vehicular Traffic Heavy Duty: Non-Deliberate Vehicular
Traffic Heavy Duty: Non-Deliberate Vehicular
Traffic Handhole-type products deployed in any
environment are subjected to the following types of traffic loading:
Vertical Cover Load, Vertical Sidewall Load, Lateral Sidewall Load, and
Long-Term Lateral Sidewall Load. Telcordia GR-902, Generic Requirements
for Handholes and Other Below-Ground Splice Vaults, contains detailed
industry requirements for handholes, and includes specific loading requirements
for the defined application environments. It provides explicit
correlations to other standards such as ANSI/SCTE-77, AASHTO specifications, and
ASTM C857. = Corrosion resistance =
Corrosion in outside plant telecommunications network components is
caused by exposure to the effects of temperature, humidity, electrical power,
and contaminants. Corrosion resistance criteria for these network components
are based on the environments to which they are exposed.
Outside plant environments can be above-ground, underground, buried, or
underwater. Industry requirements document Telcordia GR-2836 defines these
environments and provides corrosion resistance criteria for the
telecommunications equipment in each. It also includes references to various
associated ASTM Standards. Above-ground plant
Above-ground plant includes all the telecommunications equipment physically
located on or above the ground. This includes enclosures such as huts,
cabinets, and pedestals, and the equipment mounted therein. It also
includes pole-mounted equipment and cases, and pole-line hardware.
Above-ground plant can be exposed to extreme temperatures, and to humidity
that varies with the seasons and with daily temperature changes. When humidity
condenses on the surfaces of outdoor apparatus or equipment, the corrosivity
of the moisture layer can be increased by industrial pollutants that render the
condensate moisture corrosive. In sea coastal areas, wind-borne, salt-laden
water droplets can deposit on exposed components.
Near large cultivated areas, where fertilizers are applied by airplanes,
the wind may carry nitrates, phosphates, and ammonium compounds to settle on
metallic components of the above-ground telephone plant. Similarly, in
residential areas, lawn fertilizers and herbicides can cause corrosion. In
regions with snow, the salts used to melt snow and ice on roadways can
accelerate corrosion. Under extreme conditions, pedestals and cabinets may
be flooded with water that contains mud and corrosive salts. Corrosion of these
flooded components may be accelerated by the presence of dc voltages used to
power the networks. Secretions from insects can also accelerate corrosion.
Finally, chewing by rodents may expose metallic components, normally protected
by a polymer or paint coating, to a corrosive environment.
Underground plant Underground plant includes all the
telecommunications equipment installed in underground structures such as
utility holes, Controlled Environment Vaults, and ducts, along with associated
hardware. Underground plant can be exposed to waters containing
water-soluble salts of the native soil. Utility holes often show evidence of
corrosion of support hardware and bonding ribbons that is caused by
sulfate-reducing bacteria. The environment in utility holes and ducts
can be made corrosive by man-made chemicals such as industrial effluent,
fertilizers, and de-icing salts. Protective plastic coatings and cable
jackets can rapidly deteriorate from leaking steam pipes present in many
urban areas and from gasoline leaking from underground storage tanks.
The most aggressive contributor to corrosion of underground plant is dc
stray current from electrified rail transportation systems, cathodic
protection rectifiers, or welding and mining operations. Although such dc
currents are mostly dealt with “after the fact” using protective systems, some
of the protection has to be included at the manufacturing stage. This protection
may include insulating covers on cable shields, or nonmetallic components or
coatings for apparatus. Buried plant
Buried plant consists of telecommunications equipment such as
cables, splice closures, lower parts of pedestals, and grounding systems
directly buried in the soil. Buried plant can be exposed to the same
corrosive environment as underground plant. In addition, attack by gophers
can expose underlying components to corrosion attack.
Underwater plant Underwater plant includes all
telecommunications equipment located beneath the surface of a body of water.
This includes cables and repeaters. The water can range from relatively pure, to
brackish, to badly contaminated with industrial effluent.
See also Inside plant
Further reading Discount-Low-Voltage.com Blog – How
Outside Plant Cable is Made References
This article incorporates public domain material from the General Services
Administration document "Federal Standard 1037C".