To connect two or more computers or networking devices in a network, network cables are used. There are three types of network cables; coaxial, twisted-pair, and fiber-optic.
This cable contains a conductor, insulator, braiding, and sheath. The sheath covers the braiding, the braiding covers the insulation, and the insulation covers the conductor.
The following image shows these components.
This is the outer layer of the coaxial cable. It protects the cable from physical damage.
This shield protects signals from external interference and noise. This shield is built from the same metal that is used to build the core.
Insulation protects the core. It also keeps the core separate from the braided shield. Since both the core and the braided shield use the same metal, without this layer, they will touch each other and create a short-circuit in the wire.
The conductor carries electromagnetic signals. Based on conductor a coaxial cable can be categorized into two types; single-core coaxial cable and multi-core coaxial cable.
A single-core coaxial cable uses a single central metal (usually copper) conductor, while a multi-core coaxial cable uses multiple thin strands of metal wires. The following image shows both types of cable.
Coaxial cables in computer networks
The coaxial cables were not primarily developed for the computer network. These cables were developed for general purposes. They were in use even before computer networks came into existence. They are still used even their use in computer networks has been completely discontinued.
At the beginning of computer networking, when there were no dedicated media cables available for computer networks, network administrators began using coaxial cables to build computer networks.
Because of its low cost and long durability, coaxial cables were used in computer networking for nearly two decades (the 80s and 90s). Coaxial cables are no longer used to build any type of computer network.
Specifications of coaxial cables
Coaxial cables have been in use for the last four decades. During these years, based on several factors such as the thickness of the sheath, the metal of the conductor, and the material used in insulation, hundreds of specifications have been created to specify the characteristics of coaxial cables.
From these specifications, only a few were used in computer networks. The following table lists them.
|RG-6||75||18||Solid copper||Used in cable network to provide cable Internet service and cable TV over long distances.|
|RG-8||50||10||Solid copper||Used in the earliest computer networks. This cable was used as the backbone cable in the bus topology. In Ethernet standards, this cable is documented as the 10base5 Thicknet cable.|
|RG-58||50||24||Several thin strands of copper||This cable is thinner, easier to handle and install than the RG-8 cable. This cable was used to connect a system with the backbone cable. In Ethernet standards, this cable is documented as the 10base2 Thinnet cable.|
|RG-59||75||20 – 22||Solid copper||Used in cable networks to provide short-distance service.|
- Coaxial cable uses RG rating to measure the materials used in shielding and conducting cores.
- RG stands for the Radio Guide. Coaxial cable mainly uses radio frequencies in transmission.
- Impedance is the resistance that controls the signals. It is expressed in the ohms.
- AWG stands for American Wire Gauge. It is used to measure the size of the core. The larger the AWG size, the smaller the diameter of the core wire.
The twisted-pair cable was primarily developed for computer networks. This cable is also known as Ethernet cable. Almost all modern LAN computer networks use this cable.
This cable consists of color-coded pairs of insulated copper wires. Every two wires are twisted around each other to form pair. Usually, there are four pairs. Each pair has one solid color and one stripped color wire. Solid colors are blue, brown, green, and orange. In stripped color, the solid color is mixed with the white color.
Based on how pairs are stripped in the plastic sheath, there are two types of twisted-pair cable; UTP and STP.
In the UTP (Unshielded twisted-pair) cable, all pairs are wrapped in a single plastic sheath.
In the STP (Shielded twisted-pair) cable, each pair is wrapped with an additional metal shield, then all pairs are wrapped in a single outer plastic sheath.
Similarities and differences between STP and UTP cables
- Both STP and UTP can transmit data at 10Mbps, 100Mbps, 1Gbps, and 10Gbps.
- Since the STP cable contains more materials, it is more expensive than the UTP cable.
- Both cables use the same RJ-45 (registered jack) modular connectors.
- Both cables can accommodate a maximum of 1024 nodes in each segment.
- The STP provides more noise and EMI resistance than the UTP cable.
- The maximum segment length for both cables is 100 meters or 328 feet.
The following image shows both types of twisted-pair cables.
To learn how twisted-pair cables are used in the LAN network, you can check the following tutorial.
This tutorial explains how the twisted-pair cable works and how it is used to connect different networking devices in a network.
The TIA/EIA specifies standards for the twisted-pair cable. The first standards were released in 1991, known as TIA/EIA 568. Since then, these standards have been continually revised to cover the latest technologies and developments of the transmission media.
The TIA/EIA 568 divides the twisted-pair cable into several categories. The following table lists the most common and popular categories of twisted-pair cable.
|Category/name of the cable||Maximum supported speed||Bandwidth/support signals rate||Ethernet standard||Description|
|Cat 1||1Mbps||1MHz||Not used for data||This cable contains only two pairs (4 wires). This cable was used in the telephone network for voice transmission.|
|Cat 2||4Mbps||10MHz||Token Ring||This cable and all further cables have a minimum of 8 wires (4 pairs). This cable was used in the token-ring network.|
|Cat 3||10Mbps||16MHz||10BASE-T Ethernet||This is the first Ethernet cable that was used in LAN networks.|
|Cat 4||20Mbps||20MHz||Token Ring||This cable was used in advanced Token-ring networks.|
|Cat 5||100Mbps||100MHz||100BASE-T Ethernet||This cable was used in advanced (fast) LAN networks.|
|Cat 5e||1000Mbps||100MHz||1000BASE-T Ethernet||This cable/category is the minimum requirement for all modern LAN networks.|
|Cat 6||10Gbps||250MHz||10GBASE-T Ethernet||This cable uses a plastic core to prevent cross-talk between twisted-pair. It also uses a fire-resistant plastic sheath.|
|Cat 6a||10Gbps||500MHz||10GBASE-T Ethernet||This cable reduces attenuation and cross-talk. This cable also potentially removes the length limit. This is the recommended cable for all modern Ethernet LAN networks.|
|Cat 7||10Gbps||600MHz||Not drafted yet||This cable sets a base for further development. This cable uses multiple twisted-pair and shields each pair by its plastic sheath.|
- Cat 1, 2, 3, 4, 5 are outdated and not used in any modern LAN network.
- Cat 7 is still a new technology and not commonly used.
- Cat 5e, 6, 6a are the commonly used twisted-pair cables.
Fiber optic cable
This cable consists of a core, cladding, buffer, and jacket. The core is made from thin strands of glass or plastic that can carry data over a long distance. The core is wrapped in the cladding; the cladding is wrapped in the buffer, and the buffer is wrapped in the jacket.
- Core carries the data signals in the form of light.
- Cladding reflects light back to the core.
- Buffer protects the light from leaking.
- The jacket protects the cable from physical damage.
Fiber optic cable is completely immune to EMI and RFI. This cable can transmit data over a long distance at the highest speed. It can transmit data up to 40 kilometers at the speed of 100Gbps.
Fiber optic uses light to send data. It reflects light from one endpoint to another. Based on how many beams of light are transmitted at a given time, there are two types of fiber optical cable; SMF and MMF.
SMF (Single-mode fiber) optical cable
This cable carries only a single beam of light. This is more reliable and supports much higher bandwidth and longer distances than the MMF cable. This cable uses a laser as the light source and transmits 1300 or 1550 nano-meter wavelengths of light.
MMF (multi-mode fiber) optical cable
This cable carries multiple beams of light. Because of multiple beams, this cable carries much more data than the SMF cable. This cable is used for shorter distances. This cable uses an LED as the light source and transmits 850 or 1300 nano-meter wavelengths of light.