Guided Media

In this tutorial, you will learn about the concept of Guided Media. You will also learn what are the types, features, applications, advantages and disadvantages of guided media, and how guided media is used in computer networks.

Contents:

1. What is Guided Media?
2. Types of Guided Media
3. Twisted Pair Cable
4. Types of Twisted Pair Cable
5. Coaxial Cable
6. Fiber Optic Cable
7. Comparison between different Guided Media
8. Performance of Guided Media

What is Guided Media?

We know that media is one of the responsibilities of the physical layer. Generally, the media is controlled by the physical layer and is used for the actual transmission of bits from the sender’s physical layer to the receiver’s physical layer. There are two types of media, guided media, and unguided media. We will discuss Guided Media in this tutorial.

Guided media is a way of physically connecting devices to a network. Guided media is used when devices need to be connected to a network using cables. For example, connecting end devices to switches using cables is known as guided or wired networks. Guided media is also called wired media.

• Guided media uses cables between devices to transmit bits.
  Each device has a NIC (Network Interface Card), which connects to an intermediary device port using a cable on the network.
• Guided media uses Ethernet NIC to connect to the network, while unguided media uses a wireless LAN NIC to connect to the network.

Types of Guided Media

So, we understood the Guided media definition. Now, let’s see what types of guided media are used to transmit bits over a computer network.

There are 3 types of Guided media as follows:

1. Twisted-Pair Cable
2. Coaxial Cable
3. Fiber-Optic Cable

• Twisted Pair Cable: It is also known as copper cabling and is one of the most commonly used cablings in networks. Two insulated copper cables are twisted together in a helical form to prevent crosstalk and physical damage.
• Coaxial Cable: In a coaxial cable, two conductors share the same axis and are protected by insulators.
• Fiber Optic Cable: Fiber optic is made of glass and is very thin like hair. It is expensive and difficult to install as compared to twisted pair cable and coaxial cable. The core of the fiber optic cable is surrounded by cladding to prevent loss of data.

Twisted Pair Cable

Twisted pair cable is one of the types of guided media. It is commonly used in today’s networks to transmit bits from the sender’s physical layer to the receiver’s physical layer. It is made up of two insulated copper cables that are twisted together in a helical form to prevent crosstalk and physical damage.

The diagram below describes the twisted pair cable.

The diagram above shows that two conductors insulated by plastic covers (insulators) are twisted together in a helical form to prevent physical damage and crosstalk.

• The purpose of twisting cables is to reduce crosstalk. When two cables are twisted, each one produces opposite waves that cancel out each other, which reduces the noise on a channel.
• In twisted pair cable, one copper cable is used to send the signal to the receiver and the other is used for earthing (grounding) purposes.

Types of Twisted Pair Cable

There are two types of twisted pair cable used on a network. They are as follows:

1. Unshielded Twisted Pair Cable (UTP)
2. Shielded Twisted Pair Cable (STP)

• Unshielded Twisted Pair Cable: UTP cables are commonly used to connect hosts to intermediary devices on a network using an RJ-45 connector. UTP cables consist of four different colored pairs of wires (orange, green, blue, and brown) that are shielded by a plastic sheath to prevent loss or damage to the signal.
• Straight through cable and crossover cable are the types of UTP cables.
• Straight-through cables are used to connect different types of devices on a network. For example, to connect end devices to switches or to connect switches to routers.
• Crossover cables are used to connect similar types of devices on a network. For example, to connect end device to end device or to connect router to router.
• Shielded Twisted Pair Cable: STP is more expensive than UTP and difficult to set up. The pair of the insulated conductor is shielded by metal.
• STP prevents crosstalk better than UTP. Both STP and UTP use RJ-45 connectors to connect devices.
• STP cable has 4 types of colored cables that are twisted together and wrapped with a braided shield, the braided shield is also protected by foil or metal to prevent physical damage.

The below diagram describes the types of Twisted Pair cable.

The diagram above shows that unshielded twisted pair cable (UTP) and shielded twisted pair cable (STP) are types of twisted-pair cables. It also shows that STP has a metal shield due to which it is costlier than UTP.

Coaxial Cable

Coaxial cable has two conductors on the same axis that shield the cable. A copper cable surrounded by a copper conductor transmits electronic signals. The copper conductor is also shielded by an insulating material that acts as a second wire. And the whole cable is protected by the jacket.

• Coaxial cable has two conductors, the inner conductor and the outer conductor. The inner conductor of the coaxial cable transmits electronic signals, and the outer conductor is used to prevent noise on the channel.
• Bayonet Neill Concelman (BNC), N-type, and F-type are the types of connectors used in coaxial cable.
• BNC is the most commonly used connector of coaxial cable in Ethernet networks and cable TV.

The diagram below describes the coaxial cable.

The above diagram shows the architecture of the coaxial cable. It shows that the inner conductor and outer conductor are shielded by insulators, and the whole cable is protected by an outer jacket that prevents physical damage.

Fiber Optic Cable

Fiber optic cables are made of glass and transmit bits in the form of light over the communication channel. Fiber optic cable is much more expensive than a twisted pair cable and a coaxial cable.

• Signals in fiber optic cable can travel very long distances because it provides high bandwidth. The signal loss in fiber optic cable is negligible. The fiber-optic cable transmits signals with very little attenuation.
• There are two types of fiber optic cables as follows:
1. Single-mode fiber (SMF)
2. Multimode fiber (MMF)
• Single-mode fiber: It is very expensive and is used when the signal has to travel a very long distance. It sends the signal in light format. SMF is used in cable TV connections.
• Multimode fiber: The core of the MMF is larger than that of the SMF and transmits the signal in the form of a light pulse. It is used in LAN networks that have a range of about 500 meters.
• SC (Subscriber Connector), ST (Straight Tip), Lucent Connector (LC), and Duplex Multimode LC (DMLC) are types of fiber optic connectors.

The diagram below describes the types of fiber optics.

The above diagram describes two types of fiber optics. It also shows that the glass core of the single-mode fiber is less than the glass core of the multimode fiber. In SMF, light travels in a single path, whereas in MMF, light travels in multiple paths.

Comparison between Different Guided Media

The table below shows a comparison between the different types of Guided media.

Performance of Guided Media

Now we have some basic ideas about guided media. So let’s understand the performance of Guided Media.

• As we know that in a twisted pair cable, the cables are twisted which reduces the crosstalk. But it still has the problem of attenuation. Because when the frequency increases, the energy in the signal also increases, and hence the attenuation in the signal also increases.
• Similarly, coaxial cable has higher bandwidth, due to which it has higher signal attenuation than twisted pair cable. Therefore, to overcome attenuation problem in coaxial cables and twisted pair cables, repeaters are used to repeat weak signals to travel greater distances.
• The signal attenuation in fiber-optic cables is negligible compared to twisted pair and coaxial cables. So when fiber optic cable is used, very few repeaters are used on the network.