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 (such as conduit, cabinets, tower or poles), and any associated hardware (such as repeaters) 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 (MDF) 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.
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 (for example, distribution frames are generally protected by a street side cabinet) 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-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 (SAI).
- 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 (DSLAM) supporting DSL service.
Protecting Equipment in the Outside Plant
|This section needs additional citations for verification. (February 2011)|
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 (OSP) 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 are 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 (−40°F) to 46°C (115°F), 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 (OSP) contains the most recent industry data regarding each Class described above. It also discusses what is currently happening in ATIS and Underwriters Laboratories (UL)
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 (EMI), 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 (OSP) 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 (e.g., pulling or blowing cables), 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 (Up to Class 5 Vehicles)
- Heavy Duty: Non-Deliberate (Incidental) Vehicular Traffic (Up to Class 7 Vehicles)
- Heavy Duty: Non-Deliberate (Incidental) Vehicular Traffic (Up to Class 8 Vehicles)
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.
- "Telecommunications: Glossary of Telecommunication Terms". Retrieved 2010-02-02.
- "Outside Plant Cabling". Retrieved 2010-02-02.
- "Preparing for Outside Plant Installation". Retrieved 2010-02-02.
- "Understand Air Pressure Systems for OSP Cabling". Retrieved 2010-02-02.
- "Protecting Your Assets with Bonding and Grounding". Retrieved 2010-02-02.
- "Outside Plant: Basic Elements". Retrieved 2010-02-02.
- ANSI/SCTE-77, Specification for Underground Enclosure Integrity
- American Association of State Highway and Transportation Officials (AASHTO)
- American Society for Testing and Materials (ASTM) C857, Standard Practice for Minimum Structural Design Loading for Underground Precast Concrete Utility Structures
- This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).