ii Radio Wave Unguided Radio wave Radio waves are electromagnetic waves that travel throughout free space and have a frequency range of 3 kHz to 300 MHz. Since radio waves are omnidirectional, signals can go in any direction. While the sending and receiving antennas are not aligned when it comes to radio waves, any receiving antenna can pick up the wave that the sending antenna sends. The wave length ranges from 1 mm to 100 km. Easily interfere with other signals sent at the same frequency range. Radio waves can penetrate walls and can be received in the building. Radio waves can travel long distance – suitable for long distance broadcasting such as AM radio. Radio waves are used for multicast communications, such as radio and television, paging systems & cellular phones. 43
ii Micro Wave Unguided Micro wave Microwaves are electromagnetic waves with a frequency range of 300 MHz to 300 GHz. Microwave waves range in length from 1 mm to 1 m. The path that a microwave takes while traveling is straight, hence it cannot pass through anything. Therefore, line of sight is necessary for communication. Microwave propagation is highly directional (line-ofsight propagation) – used Directional Antenna. Short distance: It is inexpensive for short distance. Long distance: It is expensive as it requires a higher tower for a longer distance. Attenuation: Attenuation means loss of signal. It is affected by environmental conditions and antenna size. Microwaves are used for long distance telephone communications using repeaters, short point-to-point transmission between buildings to connect their LANs, and satellite communication . 44
ii Infrared Infrared 45 The term "infrared radiation" (IR), also known as "infrared," refers to a part of the electromagnetic radiation spectrum with wavelengths between about 700 nanometers and one millimeter. While being shorter than radio waves, infrared waves are longer than visible light waves. Accordingly, the frequencies of IR, which range from around 300 Gigahertz to 400 Terahertz (THz), are greater than microwave frequencies but lower than visible light frequencies. The longer infrared waves can be detected by heat sensors even though infrared light is undetectable to the human eye. However, there are certain similarities between infrared and visible light. Infrared light can be concentrated, reflected, and polarized just like visible light. DISCOVERY OF INFRARED In 1800, William Herschel conducted an experiment measuring the difference in temperature between the colors in the visible spectrum. He placed thermometers within each color of the visible spectrum. The results showed an increase in temperature from blue to red. When he noticed an even warmer temperature measurement just beyond the red end of the visible spectrum, Herschel had discovered infrared light! Unguided .https://science.nasa.gov/ems/07_infraredwaves
ii Unguided Medias Unguided Medias Comparison 46 Basis Radio wave Microwave Infrared Direction These are omnidirectional in nature. These are unidirectional in nature. These are unidirectional in nature. Penetration At low frequency, they can penetrate through solid objects and walls but high frequency they bounce off the obstacle. At low frequency, they can penetrate through solid objects and walls. at high frequency, they cannot penetrate. They cannot penetrate through any solid object and walls. Frequency range Frequency range: 3 KHz to 300MHz. Frequency range: 300MHz to 300 GHz Frequency range: 300 GHz to 400 THz. Security These offers poor security. These offers medium security. These offers high security.
ii Unguided Medias Unguided Medias Comparison 47 Basis Radio wave Microwave Infrared Attenuation Attenuation is high. Attenuation is variable. Attenuation is low. Government License Some frequencies in the radiowaves require government license to use these. Some frequencies in the microwaves require government license to use these There is no need of government license to use these waves. Usage Cost Setup and usage Cost is moderate. Setup and usage Cost is high. Usage Cost is very less. Communication These are used in long distance communication. These are used in long distance communication. These are not used in long distance communication.
Comparison of FDM, TDM and WDM ii PAST YEAR FINAL EXAM QUESTIONS (JUN 2019) 48 Identify FIVE (5) reasons why fiber optic is more reliable to be used as compared to the conventional electrical cable (copper cable) [10 marks] [2 mark x 5 items = 10 marks] Basis Twisted Pair Coaxial Fiber Optic Electromagnetic interference (EMI) EMI can take place. EMI is reduced to shielding. EMI is not present Attenuation In twisted pair cable has very high attenuation. In coaxial cable has low attenuation. In optical fiber cable has very low attenuation. Data rate Twisted pair cable supports a low data rate. Moderately high data rate. Very high data rate. Repeater Spacing Repeater spacing is 2-10 km. Repeater spacing is 1- 10 km. Repeater spacing is 10- 100 km. Security Security is not guaranteed of the transmitted signal. Security is not guaranteed of the transmitted signal. Security is guaranteed of the transmitted signal.
Comparison of FDM, TDM and WDM ii PAST YEAR FINAL EXAM QUESTIONS (SESI JUN 2020) 49 List THREE (3) advantages and disadvantages of fiber optic cable. [6marks] Greater capacity and higher bandwidth - Data rates of hundreds of Gbps. Smaller size & light weight Lower signal attenuation (signal loss) - A signal can run for 50km without requiring regeneration(repeater). No crosstalk (no light leaking) Immunity to Electromagnetic Interference (EMI) Highly secure (no light leaking) Resistance to corrosive materials. Glass is more resistant to corrosive materials than copper. Advantages: 1. 2. 3. 4. 5. 6. 7. [Any 3 answer = 3 marks] 1.Not easy to install and maintain - Require expertise to do maintenance and installation of cable. 2.Unidirectional light propagation – Propagation of light is unidirectional. Two fibers are needed for bidirectional. 3.Expensive cost - more expensive interfaces than electrical interfaces used with other types (twisted, coaxial). Disadvantages: 1. 2. 3. [Any 3 answer = 3 marks]
Comparison of FDM, TDM and WDM ii PAST YEAR FINAL EXAM QUESTIONS (SESI JUN 2020) 50 Mr. Sanjay planning to transfer data using optical form of signal for transmission. With the aid of diagram for the transmission medium, write the characteristic of the fiber optic including TWO (2) comparison with conventional electrical cable. [9 marks] Fiber optic carry information by light signal Consist of core, cladding, coating and jacket There are 3 elements in Optical Fiber Communication; Light Source (Transmitter) Fiber Optic Cable (Transmission Medium) Photo Detector (Receiver) Fiber optic has 3 propagation modes ; step index, multimode step index and multimode graded index Characteristics 1. 2. 3. a. b. c. 4. [2 marks] Buffer Core Outer jacket Cladding [Choose any 3 answer = 3 marks]
Comparison of FDM, TDM and WDM ii PAST YEAR FINAL EXAM QUESTIONS (SESI JUN 2020) 51 Mr. Sanjay planning to transfer data using optical form of signal for transmission. With the aid of diagram for the transmission medium, write the characteristic of the fiber optic including TWO (2) comparison with conventional electrical cable. [9 marks] [Choose any 2 answer = 4 marks] Basis Twisted Pair Coaxial Fiber Optic (EMI) EMI can take place. EMI is reduced to shielding. EMI is not present Installation Easy installation. Fairly easy installation. Difficult to install. Attenuation In twisted pair cable has very high attenuation. In coaxial cable has low attenuation. In optical fiber cable has very low attenuation. Data rate Twisted pair cable supports a low data rate. Moderately high data rate. Very high data rate. Cost The cost is very low. Cost is moderate Cost is expensive. [Total marks = 2 + 3 + 4 = 9 marks]
Comparison of FDM, TDM and WDM ii PAST YEAR FINAL EXAM QUESTIONS (SESI I : 2022/2023) 52 Unshielded twisted pair (UTP) Shielded twisted pair (STP) UTP cable is a twisted pair cable with wires that are twisted together. It is enclosed within a foil or mesh shield. The price of UTP is lower as compared to the STP. The price of STP is much costlier than UTP. Installation of UTP cables is easy as they are lighter, small in size, and flexible. Installation of STP cable is quite difficult as compared to the UTP. Its size is heavy, bigger, and stiffer. In UTP, the electromagnetic interference is more than the STP while transferring the signal to the transmission media. It reduces electromagnetic interference while transferring the signal to the transmission media. Mrs Najwa is a telecommunication technician. She plans to provide a medium for telephone network using twisted pair cables between local customer home areas (LANs). Explain TWO(2) types of twisted pair cables and their properties. [6 marks] [Any 2 answer = 4 marks] [1 mark] [1 mark]
Comparison of FDM, TDM and WDM ii 53 REFERENCES Advantages of Optical Fiber, https://community.fs.com/blog/ the-advantages-and-disadvantages-of-opticalfibers.html Applications of fiber optic cable https://www.stl.tech/blog/types-of-optical-fiber/ Bernard Sklar (2001). Digital Digital Communications: Fundamentals and Application (2nd ed). Prentice Hall. (ISBN10: 0130847887, ISBN13: 9780130847881) Borzycki, K. (2018). FTTx Access Networks: Technical Developments and Standardization. InTech. doi: 10.5772/intechopen.71785 Dasan, M., Francis, F., T. Sarath, K., Dipin, E., & Srinivas, T. (2019). Optically Multiplexed Systems: Wavelength Division Multiplexing. IntechOpen. doi: 10.5772/intechopen.88086 Difference between Radio wave, Microwave and Infrared waves, https://www.geeksforgeeks.org/differencebetween-radio-wave-microwave-and-infraredwaves/ Difference between Radio Waves and Microwaves, https://www.javatpoint.com/difference-betweenradio-waves-and-microwaves
Comparison of FDM, TDM and WDM ii 54 REFERENCES Differences between UTP and STP, https://www.javatpoint. com/utp-vs-stp Electromagnetic Spectrum 101: Radio, Microwave, and Infrared, https://gamma-sci.com/2021/07/02/ electromagnetic-spectrum-101-radio-microwaveand-infrared/ Electromagnetic waves, https://www.bbc.co.uk/bitesize/ guides/z32f4qt/revision/2 Hwei Hsu (2002). Schaum’s Outline of Theory and Problems of Analog and Digital Communications (2nd ed). McGraw-Hills. ISBN-10: 0071402284. ISBN-13: 978- 0071402286 Infrared – Infrared Radiation, https://www.infratec.eu/ sensor-division/service-support/glossary/infraredradiation/ Infrared radiation (IR), https://www.techtarget.com/ searchnetworking/definition/infrared-radiation Infrared Waves, https://science.nasa.gov/ems/ 07_infraredwaves
Comparison of FDM, TDM and WDM ii 55 REFERENCES M. Forouzan, B.A. (2012). Data Communications and Networking (5th ed). Mc Graw Hill. (ISBN: 978-0-07- 131586-9) Mohammady, S. (Ed.). (2019). Multiplexing. IntechOpen. doi: 10.5772/intechopen.78513 Multiplexing in Computer Network, https://www.tutorial spoint.com/data_communication_computer _network/physical_layer_multiplexing.htm Multiplexing: An Intro to How it Works, https://www.techopedia.com/2/28320/internet /web-services/multiplexing-an-intro-to-how-it -works Nandalal, V., & Sumalatha, M. S. (2019). Multiplexing. IntechOpen. doi: 10.5772/intechopen.85866 Rjeb, A., Fathallah, H., & Machhout, M. (2022). Multiplexing, Transmission and De-Multiplexing of OAM Modes through Specialty Fibers. IntechOpen. doi: 10.5772/intechopen.101340 Structure of fiber optic Cable, https://onlineclassnotes.com/ what-is-optical-fiber-briefly-describe-thestructure-of-optical-fiber-what-arecharacteristics-of-optical-fiber/
Comparison of FDM, TDM and WDM ii 56 REFERENCES Wayne T. (2004). Electronic Communication Systems: Fundamentals Through Advance (6th ed). Prentice Hall. ISBN-10: 0130453501 or ISBN-13: 9780130453501 What Is Infrared?, https://www.livescience.com/50260- infrared-radiation.html What is Multiplexing : Types & Their Applications, https://www.elprocus.com/what-is-multiplexingtypes-and-their-applications/ Xi, P. (Ed.). (2012). Optical Devices in Communication and Computation. InTech. doi: 10.5772/2859
Comparison of FDM, TDM and WDM ii 57 "The world is a complex place, and the influence of the media in its representation and its power is remarkable amplifier of emotion, and of illusions." Tariq ramadan
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