Physical Networking Essay
Application: (1) A program running on a computer. (2) A system, the transmission method of which is supported by telecommunications cabling, such as 100Base-TX Ethernet, or digital voice. (Oliviero & Woodward, 2011) Unshielded Twisted-Pair: (1) A pair of copper wires twisted together with no electromagnetic shielding around them. (2) A cable containing multiple pairs of UTP wire. Each wire pair is twisted many times per foot (higher grade UTP cable can have more than 20 twists per foot). The twists serve to cancel out electromagnetic interference that the trans-mission of electrical signal through the pairs generates. An unshielded jacket made of some type of plastic then surrounds the individual twisted pairs. Twisted-pair cabling includes no shielding. UTP most often refers to the 100 ohm Categories 3, 5e, and 6 cables speciﬁed in the ANSI/TIA/EIA-568-B standard. (Oliviero & Woodward, 2011) Shielded Twisted-Pair: A type of twisted-pair cable in which the pairs are enclosed in an outer braided shield, although individual pairs may also be shielded. STP most often refers to the 150 ohm IBM Type 1, 2, 6, 8, and 9 cables used with Token Ring networks. Unlike UTP cabling, the pairs in STP cable have an individual shield, and the individual shielded cables are wrapped in an overall shield.
The primary advantages of STP cable are that it has less attenuation at higher frequencies and is less susceptible to EMI. Since the advent of standards-based structured wiring, STP cable is rarely used in the United States. (Oliviero & Woodward, 2011) Fiber-Optic Cable: Cable containing one or more optical ﬁbers. (Oliviero & Woodward, 2011) Dark Fiber: An unused ﬁber; a ﬁber carrying no light. Common when extra ﬁber capacity is installed. (Oliviero & Woodward, 2011) Coaxial Cable: Also called coax. Coaxial cable was invented in 1929 and was in common use by the phone company by the 1940s. Today it is commonly used for cable TV and by older Ethernet; twisted-pair cabling has become the desirable way to install Ethernet networks. It is called coaxial because it has a single conductor surrounded by insulation and then a layer of shielding (which is also a conductor) so the two conductors share a single axis; hence “co”-axial. The outer shielding serves as a second conductor, ground, and to reduce the effects of EMI.
They can be used at high bandwidths over long distances. (Oliviero & Woodward, 2011) Plenum: The air-handling space between the walls, under structural ﬂoors, and above drop ceilings when used to circulate and otherwise handle air in a building. Plenum-grade cable can be run through these spaces if local building codes permit it. (Oliviero & Woodward, 2011) Riser: (1) A designation for a type of cable run between ﬂoors Fire-code rating for indoor cable that is certiﬁed to pass through the vertical shaft from ﬂoor to ﬂoor. (2) A space for indoor cables that allow cables to pass between ﬂoors, normally a vertical shaft or space. (Oliviero & Woodward, 2011) Rip Cord: A length of string built into optical ﬁber cables that are pulled to split the outer jacket of the cable without using a blade. (Oliviero & Woodward, 2011) Core: The central part of a single optical ﬁber in which the light signal is transmitted. Common core sizes are 8.3 microns, 50 microns, and 62.5 microns.
The core is sur-rounded by a cladding that has a higher refractive index that keeps the light inside the core. The core is typically made of glass or plastic. (Oliviero & Woodward, 2011) Attenuation: A general term indicating a decrease in power (loss of signal) from one point to another. This loss can be a loss of electrical signal or light strength. In optical ﬁbers, it is measured in decibels per kilometer (dB/km) at a speciﬁed wavelength. The loss is measured as a ratio of input power to output power. Attenuation is caused by poor-quality connections, defects in the cable, and loss due to heat. The lower the attenuation value, the better it is. Attenuation is the opposite of gain. See Chapter 1 for additional information on attenuation and the use of decibels. (Oliviero & Woodward, 2011) Noise: In a cable or circuit, any extraneous signal (electromagnetic energy) that interferes with the desired signal normally present in or passing through the system. (Oliviero & Woodward, 2011) Headroom: The number of decibels by which a system exceeds the minimum deﬁned requirements.
The beneﬁt of more headroom is that it reduces the bit-error rate (BER) and provides a performance safety net to help ensure that current and future high-speed applications will run at peak accuracy, efﬁciency, and throughput. Also called the overhead or margin. (Oliviero & Woodward, 2011) ANSI: American National Standards Institute (ANSI) in 1918 as a private, nonproﬁt membership organization sustained by its membership. ANSI’s mission is to encourage voluntary compliance with standards and methods. ANSI’s membership includes almost 1,400 private companies and government organizations in the United States as well as international members. (Oliviero & Woodward, 2011) NFPA: The ﬁre test method that measures ﬂame spread, peak smoke optical density, and average smoke optical density. Formerly referred to as, UL 910. Cables are required to pass this test and be listed by a nationally recognized test laboratory (e.g., UL or ETL) for the cables to be allowed to be placed in plenum spaces. (Oliviero & Woodward, 2011)
FCC: The federal agency responsible for regulating broadcast and electronic communications in the United States. (Oliviero & Woodward, 2011) NIST: The U.S. Congress established the National Institute of Standards and Technology (NIST) with several major goals in mind, including assisting in the improvement and development of manufacturing technology, improving product quality and reliability, and encouraging scientiﬁc discovery. NIST is an agency of the U.S. Department of Commerce and works with major industries to achieve its goals. (Oliviero & Woodward, 2011) OSHA: A division of the U.S. Department of Labor, the Occupational Safety and Health Administration (OSHA) was formed in 1970 with the goal of making workplaces in the United States the safest in the world.
To this end, it passes laws designed to protect employees from many types of job hazards. OSHA adopted many parts of the National Electrical Code (NEC), which was not a law unto itself, giving those adopted portions of the NEC legal status. (Oliviero & Woodward, 2011) Equipment Room: A centralized space for telecommunications equipment that serves the occupants of the building or multiple buildings in a campus environment. Usually considered distinct from a telecommunications closet because it is considered to serve a building or campus; the telecommunications closet serves only a single ﬂoor.
The equipment room is also considered distinct because of the nature of complexity of the equipment that is contained in it. (Oliviero & Woodward, 2011) Topology: The geometric physical or electrical conﬁguration describing a local communication network, as in network topology; the shape or arrangement of a system. The most common topologies are bus, ring, and star. (Oliviero & Woodward, 2011)
Oliviero, A., & Woodward, B. (2011). Cabling- The Complete Guide to Copper and Fiber-Optic Networking. (I. John Wiley & Sons, Ed.)