In the coaxial cable, the center conductor is covered with a dielectric insulator covered by a foil shield, which in turn is surrounded by an outer conductor (usually a braid). In addition, an insulating and protective outer jacket is surrounded through the whole.
Coaxial cables consist of two conductors, center or inner conductor and outer conductor. The inner conductor transmits data while outer conductor serves as a line to ground. The outer conductor provides a shield against noise. A dielectric insulator exists between these two conductors, which in turn enhances the fundamental characteristics of the coaxial cable. The whole cable is covered with an outer jacket, which is made of plastic. The coaxial cable can carry signals of higher frequency ranges than the twisted-pair cables. These cables are used in cable TV networks and Ethernet LANs.
Coaxial cables are classified into two types as follows:
Thicknet coaxial cable is a 50 ohm-thick (10 mm) coaxial cable that is used with Ethernet 10Base5 networks. This cable has a diameter of 1 centimeter (cm) for use with Ethernet. It possesses greater transmission length and noise-rejection feature. Thicknet cable is easy to install. A connecting device known as the vampire tap is used to connect thicknet cable to network devices. The vampire tap connector finally uses the attachment unit interface (AUI) cable to connect network devices to the computers.
Thinnet is a 50 ohm- thin (5mm) coaxial cable used with Ethernet 10base2 networks. This cable has an outside diameter of 0.35 cm and has low installation cost as it can be tuned and wrapped. As the installation cost is cheap, therefore, these cables are sometimes known as cheapernet. This cable is used for short distance as it support only 185 meters maximum segment length.
British Naval Connector (BNC) is used to connect network devices to Thinnet. BNC connector is usually a male connector, which is located at both the ends of a cable. The center pin of this connector is linked to center conductor. This connector also has a metal tube, which is used to connect outer cable shield. This metal tube contains a rotating ring, which is used to connect the cable to any female connector. BNC Tee connectors (BNC T connectors) are female connectors, which are used to connect two cables to a network interface card (MC). Let’s now learn about fiber optic cable.
Fiber Optic Cable
Fiber optic cable is a network cable. This cable is based on fiber optics technique. As you know, the transmission across cable is done via electrical signals. However, the transmission across fiber optic cable is done in a distinct way. Primarily, the electrical signals are commuted in optical signals. After that, these optical signals are conveyed through a narrow glass fiber strand, and then reformed in electrical form. A fiber optic cable is made up of glass or plastic, and the signal propagates in the form of light. The inner core is surrounded by a cladding of glass or plastic that is less dense than the core. These cables have a higher bandwidth and are also thinner and lighter than the metallic cables. Because of the higher bandwidth, fiber optic cables can carry more data. The main disadvantage of this type of cable is that it is quite expensive to install. A fiber optic cable is used as a transmission medium in the Ethernet media systems, such as Fiber Optic Inter-Repeater Link (FOIRL), 10BaseFL, 10BaseFP, 100BaseFX, 1000BaseLX, and 1000BaseSX.
Fiber Optic cables are classified into two primary types as follows:
- Single-Mode Fiber (SMF)
- Multi- Mode Fiber (MMF)
In SMF, the diameter of the core is too small means 10 microns. Due to its small core diameter, only a single mode of light can be propagated. Also, the coupling light in this cable becomes difficult due to small core of the cable. It uses an infrared laser as light source. Another purpose of using laser as light sources is to achieve high bandwidth. The light ray that carries the data is transmitted in a straight line and therefore enhances the speed of data transmission.
The primary advantage of SMF over MMF is that it can support higher segment lengths. For instance, SMF is able to support a segment length of 5000 meters and higher over all the Ethernets having a data transmission rate of up to 1 Gbps. With the advantages, SMF has some disadvantages too. The major disadvantage of SMF is that the installation cost is higher than MMF.
In MMF, the diameter of the core is larger than SMF that is 50 to 100 microns. Also, multiple modes of light can be propagated through the fiber optic path. Due to large core of MMF, coupling light becomes susceptible. MNIF uses inexpensive light emitting diodes (LEDs) as light sources. MMF can be classified into two types, such as graded-index and stepped-index, on the basis of refractive index. In the graded-index MMF, the refraction index of the core gradually decreases toward the outside of the core while increases toward the center of the core. This property results in abbreviating the modal dispersion of a signal. On the other hand, in the stepped-index MMF, the refraction index of the core remains uniform but with a small reduction at the core-cladding interface. Also, a lower bandwidth is supported by the stepped-index MMFs in comparison to that of the graded-index MMFs.
MMFs are available in various sizes. The mostly recommended MMF size for networking is the 62.5/125 micron where 62.5 deals with the core diameter and 125 specify the cladding. However, some other common NINIFs sizes are 50/125 microns and 100/140 microns. In addition, MMF supports a segment length of 2000 meters for Ethernet having a data transmission rate of 10 and 100 Mbps. It can also support segment length of 550 meters for Ethernet having a data transmission rate of 1Gbps.