Triple Exposure Types of Computer Network |
Mainly, there are three kinds of computer networks given below;
>>> Short description of above points <<< 1).Local Area Network (LANs) Local Area Networks, commonly known as the LANs which are originally owned privately. As the need of the organization and the components involved (networking components)LANs may be simple as connection between the two PCs or Workstation or it may be extended outside the company to connect two LANs. Local Area Networks (LANs) are the networks that are usually confined to a geographic area of small range such as within a single building, college, office, hospital, etc. LANs can be small linking as few as two computers but often link hundreds of computers used by thousands of people. The development of standard networking protocols and media has resulted in world wide growth of LANs throughout business and educational organization. 2). Wide Area Network (WANs) Wide Area Network commonly known as WANs which is mainly used to connect the different computers at any end of the world (i.e, world wide connection). WANs combine multiple LANs that are geographically separate. This is achieved by connecting the different LANs. Using services such as dedicated leased line, dial-up lines, satellite link, etc WAN can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally link using special routing protocols and filters to minimize the expense of sending data such as image, audio, video over large geographic areas. It is the network which connects countries, continents or even the whole world. 3). Metropolitan Area Network (MANs) These are the computer networks that refers to the networks of computers within city or metropolitan area. A single MANs comprises of several LANs. It is the network between the LANs and WANs. |
| Transmission Media |
Transmission medium is the physical layer or path or link or way through which the data and information are transmitted over the networks. A transmission medium can be broadly defined as anything that can carry information from a source to a destination. It is usually a free space, metallic cable or fiber optic cable. In telecommunication, transmission media can be divided into two broad categories;
>>> Short description of above points <<< I).Guided Media Guided media are those that provide the conduit from one device to another and includes twisted pair cable, co-axial cable, fiber optic cable. A signal travelling along any of these media is directed and contained by the physical limits of the medium. There are several guided media available in the markets given as below; 1). Twisted pair cable Twisted pair cable consists of two insulted strands of copper wire twisted around each other to form a pair. One of the wire is used to carry signals to the receiver and the other is used only as a ground reference. The receiver uses the difference between the two. In addition to the signal sent by the sender on one of the wires, interference and crosstalk many affect both wires and creates unwanted signal. The purpose of twisting wire is to eliminate electrical interference fro mother wires and out side resources. Twisting the wire cancels any electrical noise from the adjacent pair. The more twist per linear foot, the greater the effect. There are two types of twisted pair cable. a). Shielded twisted pair (STP) The only difference between STP and UPT is that STP has a foil or wired braid wrapped around the individual wires of the pair. The shielding designed to minimized electromagnetic interference radiation and succeptibility to crosstalk. The STP cable sues a woven copper braided jackets which is a higher quality more protective jacket than UTP. b). Unshielded twisted pair (UTP) As the name implies UPT cabling is twisted pair cabling that contains no shielding. It is the most common twisted pair cable used in communication. 2)Co-axial Cable It is made up of two conductors that share the same axis, the center is a copper wire that is insulated by a plastic coating and then wrapped with an outer conductor usually a wire braid. This outer conductor around the insulation serves as electrical shielding for the signal being carried out by the inner conductor. A tough insulating plastic tube outside the outer conductor provides physical and electrical protection. It carries the signal of high frequency ranges than those in twisted pair cable, in part because the two media are constructed quite differently. Categories of co-axial cable
3)Fiber Optics A fiber optic cable is made up of light conducting glass or plastic fibers. It can carry data signals in the form of the pulses of light. The plastic core cables are easy to install but do not carry signals as far as glass core cables. Optical fibers use total internal reflection to guide light through a channel. A glass or plastic core is surrounded by a cladding of less dense glass or plastic. The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead being refracted into it. #Propagation Mode of fiber optics 1).Multi mode propagation: It is so named because multiple beams from a light source move through the core in different paths. How these beams move within the cable depends on the structure of the core. It is further divided into two categories; i) Multi-mode step-index fiber In this mode, the density of the core remains constant form the center to the edges. A beam of light moves through this constant density in a straight line until ti reaches the interface of the core and cladding. At the interface, there is an abrupt change due to the lower density; this alters the angle of the beams motion. The term step-index refers to the suddenness of this change, which contributes to the distortion of the signal as it passes through the fiber. ii) Multi-mode graded-index fiber It decreases this distortion of the input through the cable. The word index here refers to the index of refraction. We know that the index of refraction is related to the density. A graded index fiber, therefore, is one with varying density. Density is highest at the center of the core and decreases gradually to its lowest at the edge. 2). Single mode propagation Single mode use step-index fiber and a highly focused source of light that limits beams to a small range of angles, all close to the horizontal. The single mode fiber itself is manufactured with a much smaller diameter than that of multi-mode fiber and with substantially lower density. The decrease in density results in a critical angle that is close enough to 90 degree to make the propagation of beams almost horizontal. In this phase, propagation of different beams is almost identical and delays are negligible. All the beam arrive at the destination together and can be recombined with little distortion to the signal. |
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