CABLING INFRASTRUCTURE

 

General

Outside Plant Definition

Outside plant is defined as those communications pathways, spaces and media which are located outside of the building walls. This includes, but is not limited to the cable (copper and fiber), splices, conduit, manholes, handholes, poles and hardware related to the attachment and support of the various forms of media.

Function

The function of customer-owned OSP cabling infrastructure is to provide connections between building entrance facilities, structures in a campus environment, or telecommunications pedestals or cabinets. Customer-owned OSP cabling consists of the backbone cables, splices, terminations, and patch cords or jumpers used for backbone-to-backbone connection. The customer-owned OSP cabling infrastructure shall meet the requirements of the local authority(s) and local codes.

History

Prior to the divestiture of the Bell Companies, they were the ones who looked after the OSP infrastructure. Now, owners have a choice of who owns, installs and manages the infrastructure. One of the main issues is the lack of standardization in requirements and installation methods. It is now up to the owner to take on the burden of the decision making process of what products to use and who to get to install them.

Regardless of any of the above issues, the designer has to be aware of:

Safety

The designer and installer must also be aware of the safety issues involved in working in an OSP environment. Depending on the route the installer may be working at the top of an aerial truck, or in a manhole or trench. It is everyone's responsibility to ensure that proper safety precautions are taken. If the route cannot be constructed without compromising the safety of those involved, the route should be altered.

Topology

The recommended topology for customer-owned OSP cabling is a star configuration. This is the same type of star topology that is recommended for a local area network. In the case where a star topology cannot be used, consider a hierarchical star. By implementing a star, or hierarchical star the system can be managed and maintained easier than other topologies. The same advantages of a LAN star topology can be found in a campus star topology.

In a star topology one of the buildings will act as the MC and feed out the backbone cables to the various buildings. In a hierarchical star there may be a building acting as an MC, and the another group of buildings is served by a building acting as an IC.

Other types of topologies that may be used are a bus or tree and branch topology, physical wired star/virtual ring and a ring. A ring topology may be a single path ring, a counter rotating redundant ring or several attached rings.

Each type has its disadvantages and advantages depending on the layout of the network, media chosen and applications being run, and as well, the overall goal of the network.

Recognized Cables

An OSP environment may support several applications such as CATV, LAN, WAN, and voice over a variety of distances and in a number of different physical and environmental settings. For these reasons OSP cable must be able to support all of these environments and applications. Therefore several cables are recognized by the standards. The recognized media include:

A single media may not satisfy all of the requirements of the owner, and therefore several types of media may be required. When possible the various media should use the same pathways to keep administration and costs down. In making this choice, factors to be considered include:

Bonding and Grounding

Bonding and grounding shall meet the appropriate requirements and practices of applicable authorities and codes. Additionally, grounding and bonding within buildings shall conform to ANSI/TIA/EIA-607 requirements, and the National Electrical Safety Code (NESC) between buildings. Failure to follow these standards and codes can result in interference, improper operation and possible harm to those operating the system.