Monday, January 12, 2009

Network+ Guide: Cabling


UTP - Unshielded Twisted Pair: UTP cables are found in many ethernet networks and telephone systems. For indoor telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair color code originally developed by AT&T. A typical subset of these colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables.

UTP cable is the most common cable used in computer networking. It is often used in data networks for short and medium length connections due to its relatively lower costs compared to coaxial and fiber optic cables.

Category 5 cabling issues:
- CAT5 cable runs should not exceed 100 meters.

- Since UTP cable is susceptible to magnetic interference, it is important that you do not lay data cables directly across ceiling tiles, grids, or fixtures. Use cable trays or other methods to support the cables and keep them at least 6 inches away from fluorescent, HID light fixtures or any type of compressor.

- Do not bend Category 5 cable more tightly than eight times the cable diameter (a 2-inch bend radius). This can damage the twisted pairs and degrade performance.

Fiber Optic Cabling - Fiber optic cabling is a network media in which data travels through the thin cables at the speed of light.

If you look closely at a single optical fiber, you will see that it has the following parts:

  • Core - Thin glass center of the fiber where the light travels
  • Cladding - Outer optical material surrounding the core that reflects the light back into the core
  • Buffer coating - Plastic coating that protects the fiber from damage and moisture

Optical fiber come's in two types: Single mode fibers and multi mode fibers.

Multimode fiber will allow transmission distances of up to about 10 miles and will allow the use of relatively inexpensive fiber optic transmitters and receivers. There will be bandwidth limitations of a few hundred MHz per Km of length.

Single-mode fiber on the other hand will be useful for distances well in excess of 10 miles but will require the use of single-mode transmitters (which normally use solid-state laser diodes).

Maximum distance for Ethernet over fiber:

Ethernet Standards (IEEE) Data Rate Cable Fiber Type Maximum Distance (IEEE)
Ethernet (10Base-FL) 10 Mbps 50µm or 62.5µm Multimode @ 850nm 2km
Fast Ethernet (100Base-FX) 100 Mbps 50µm or 62.5µm Multimode @ 1300nm 2km
Fast Ethernet (100Base-SX) 100 Mbps 50µm or 62.5µm Multimode @ 850nm 300m
Gigabit Ethernet (1000Base-SX) 1000 Mbps 50µm Multimode @ 850nm 550m
Gigabit Ethernet (1000Base-SX) 1000 Mbps 62.5µm Multimode @ 850nm 220m
Gigabit Ethernet (1000Base-LX) 1000 Mbps 50µm or 62.5µm Multimode @ 1300nm 550m
Gigabit Ethernet (1000Base-LX) 1000 Mbps 9µm Singlemode @1310nm 5km
Gigabit Ethernet (1000Base-LH) 1000 Mbps 9µm Singlemode @1550nm 70km

Most Common Connectors:
ST: Probably the most popular connector for multimode networks. It has a bayonet mount and a long cylindrical 2.5 mmceramic or polymer ferrule to hold the fiber. Because they're spring loaded, you have to make sure they are seated properly.

SC: The SC connector is a fiber optic connector with a push-pull latching mechanism which provides quick insertion and removal while also ensuring a positive connection.

FC: The FC connector is a fiber optic connector with a threaded body which was designed for use in high-vibration environments.

LC: Small form factor connector. Resembles a smaller SC connector.

Coaxial - A type of wire that consists of a center wire surrounded by insulation and then a grounded shield of braided wire. The shield minimizes electrical and radio frequency interference.

While still used in Ethernet networks, it is less common than Cat5/6 networks.

Ethernet Cable Summary

Specification Cable Type Maximum length
10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial 500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters

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