What is Network Cabling?

Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.

Unshielded Twisted Pair (UTP) Cable

Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded Twisted Pair (UTP) is the most popular and is generally the best option for most networks

100 Ohm UTP
 Unshielded twisted four pair (cat 5e)

The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. 
Category 1,2, and 4 are no longer used but are common in many older installations. Category 3 is common for Voice applications today (even though it is being phased out by the manufactures). 

The trend today is to install Category 5e, or Category 6 cabling of different color (white=voice, blue=data) for both Voice and Data as they will provide more "room to grow" as transmission technologies increase.

Buy the best cable you can afford

                                                                                          

                                                                                   Unshielded twisted four pair (cat 6)

                                                                              

  Category 6 is used for gigabit connections.   Comparison of Cat5e and Cat6

Cat5e is suitable for 10/100/1000baseT Ethernet for 100 meters,
when properly installed.

Cat 6 is also good for 10 gig Ethernet for 37 meters,
but that is pretty short, unless just in a server room.

There is no Cat 6e, but Cat 6A will be good for
10/100/1000/10GbaseT Ethernet for 100 meters.

A disadvantage of UTP is that it may be susceptible to radio and electrical frequency interference.

 

Shielded Twisted Pair (STP) Cable

                                                                100 Ohm F/UTP

                                                                                     Shielded twisted four pair (cat 5e)

 Shielded twisted pair (STP) is suitable for environments with electrical interference; however, the extra shielding can make the cables quite bulky. 

T-1 & T-3 Circuits

T-1 Shielded twisted two pair

The local Telco service supplier usually provides T-1 service into the entrance facility or to the "Demarc" point, and the owner or installer must take it from there. Since many LAN installers and owners are unfamiliar with the requirements for T-1 cabling, many use the wrong cabling. For short runs (less than 30 or 40 feet), just about any 100 ohm shielded cable will work, but longer runs often cause equipment to fail. Installers have tried using Category 5 UTP, 50 ohm security cable, cash register cable, or anything that will fit into a modular connector. Most do not realize that the cabling must support specific DS-1 system requirements that are defined by an ANSI specification. These include bit error rates, EMI shielding, pulse shape definition and many others. DS-1 systems are far different than LAN Category 5.

Coaxial Cable

Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield  The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.



 Coaxial cable

Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths. 

 The two types of coaxial cabling are thick coaxial and thin coaxial.

Thin coaxial cable is also referred to as thin net. Mainly used today for Surveillance equipment.1

Thick coaxial cable is Normally used for Broadband and Video today. 

One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.

Coaxial Cable Connectors

The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector . Different types of adapters are available for BNC connectors



 BNC connector

Fiber Optic Cable

Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting.

Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of the fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify, and the electronics required to make it work are more expensive. 10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals.

 
             Multimode Optical Fiber
                                   Multimode Optical Fiber
                         Singlemode Optical Fiber
                                 Singlemode Optical Fiber


                                            Fiber optic cable

Fiber Optic Connectors

The most common connectors used with fiber optic cable are the ST connector. It is barrel shaped, similar to a BNC connector,and the SC, which is becoming more popular. It has a squared face and is easier to connect in a confined space.

                                                                  SC connector     ST connector

The newer LC connector is being used with many of the newer switches' fiber optic plug- ins. It looks like a SC connector but is much smaller.

                                                                                              LC connector

To make the LC work with other types of connections, you may use jumper cord that has an LC on one end to ST on the other end (or LC to SC cord)

                                                                                 LC/ST    LC/SC

 

Installing Cable - Some of our Basic Guidelines

When running cable, it is best to follow a few simple rules:

Always use more cable than you need. Leave plenty of slack.

Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later.

Stay at least 3 feet away from fluorescent light boxes and other sources of electrical interference.

Label both ends of each cable.

Use Velcro or cable ties (snug, not tight) and never tape to keep cables in the same location together.