S.R.M. University Faculty of Engineering and Technology School of Electronics and Communication Engineering

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1 S.R.M. University Faculty of Engineering and Technology School of Electronics and Communication Engineering Question Bank Subject Code : EC459 Subject Name : Optical Networks Class : IV Year B.Tech (ECE) Unit I Fiber and Network Components Part A 1. Draw a block diagram of a fiber communication system. 2. Why fiber-optic communication is considered as the backbone of modern telecommunications? 3. What are the advantages of fiber optic communication? 4. What are the disadvantages of fiber optic communication? 5. Define the term wavelength and frequency. 6. Define the term refractive index. 7. Describe the functions of core and cladding in an optical fiber. Why are their refractive index is different? Which one has to be greater and why? 8. List the advantages of fiber optic communications over the types of communication technologies. 9. Why is it necessary to meet the total internal reflection requirement inside an optic fiber? 10. What is an acceptance angle? Why do we need to know what this angle is? 11. What is attenuation in an optical fiber? What is loss in an optical fiber? 12. List the major causes of attenuation in an optical fiber and explain their mechanisms. 13. Express the pulse spreading time caused by modal dispersion in terms of the relative refractive Index?. 14. Consider the modal dispersion for a step index multimode fiber with NA = and n1 = Evaluate pulse spreading per 1 km length. 15. Consider the model dispersion for a step index multimode fiber NA=0.200 and n1= Calculate the maximum number of bits/sec that can be transmitted over 1 km. 16. Calculate the pulse spreading due to modal dispersion and the max. no. of bits/sec that can be transmitted over 1km with a step index fiber whose parameters are given as : n1=1.4513, n2= What are the solutions to the modal dispersion problem? 18. What is chromatic dispersion? 19. Calculate the pulse spreading due to chromatic dispersion for the graded index fiber if the operating wavelength is 850nm, distance is 5km and the source s spectral width is 70nm. 20. What are bandwidth and bit rate in communication systems? 21. What is the difference between dispersion and distortion? 22. Define Bandwidth. Why are electrical and optical bandwidths are different? 23. What is the relation between bit rate and bandwidth.

2 24. Calculate the pulse spread caused by material dispersion if?x=0.5nm, L=1km and wavelength 1550nm. 25. Calculate the pulse spread caused by waveguide dispersion if?x=0.5nm, L=1km and wavelength 1550nm. 26. What does the term State of Polarization, mean? 27. Write the difference between SPM and XPM Phenomenon 28. What is Four Wave Mixing? 29. Why FWM is so important in today s optical network? 30. Write the difference between SRS and SBS. 31. Calculate the pth (SRS) and Pth (SBS) for a fiber with Aeff=72 micrometrer =2 and Leff=20km. 32. What is WDM 33. What are the components used in an optical network? 34. What is the function of an optical amplifier? 35. What are three functional types of optical amplifier? 36. What is Crosstalk in SOA? 37. What are the two major mechanism that cause crosstalk? 38. What is amplified spontaneous emission? 39. Why is erbium used in EDFA? 40. What phenomenon determines the bandwidth of an EDFA 41. What is the function of coupler? 42. Name and describe two major classes of filters 43. What are the basic characteristics of a filter? 44. Give examples of reciprocal and nonreciprocal devices 45. Explain the function of circulators and isolators. 1. List the major Causes of Attenuation in an optical fiber & explain their mechanism 2. Explain in detail about light propagation in a fiber? 3. List three major causes of dispersion in an optical fiber & Explain their mechanism 4. Explain the principle of operation of a semiconductor optical amplifier (SOA)? 5. Show the structure of an EDFA & Explain the function of each component 6. Explain how stimulation emission occurs in an EDFA 7. What is the function & the principle of operation of an isolator? Give Eg. Of isolator Applications 8. What is the function & the principle of operation of operation of a circulator? Give E.g. Of its application 9. Explain the function of Optical switches 10. Explain about Nonlinearity effects in a fiber 11. Explain the principle of operation of Fabry Perot (FP) filter? 12. Explain the principle of operation of Mach Zehnder Interferometer (MZI)? 13. Explain the function & the Principle of operation of Wavelength Converters?

3 UNIT II - Modulation, Demodulation & Design Consideration 1. Define Optical Sources 2. Show the diagram of fiber optic communication system 3. Draw the block diagram of Optical Transmitter? 4. Draw the block diagram of Optical Receiver 5. What are the advantages of optical fiber? 6. What are the major advantages of hetrostructured LED over a homostructured one? 7. What is the difference between a surface emitting LED (SLED) & Edge emitting LED (ELED) 8. What are the drawbacks of homostructured LED? 9. Calculate the internal quantum efficiency of a 1.3micro meter SLED at a forward current of 100mA assuming that 75% of the LEDs output power is coupled into an optical fiber? 10. What light source is called Lumberton? 11. Distinguish between Laser and LCD Sources 12. What are the characteristics of LASER diode? 13. What are the advantages of photo detector used as light source in fiber optic communication system? 14. Define Intensity Modulation? 15. Define direct detection? 16. What are the two methods of modulation/demodulation techniques used today in fiber optic communication system? 17. Define Sub Carrier modulation? 18. Define Sub Carrier Multiplexing? 19. What is the application of Sub carrier Multiplexing (SCM)? 20. What is the function of preamplifier? 21. Why do we need polarization maintenance adapter (PMA) at transmitter & receiver end of the coherent optic system? 22. What does coherent system work effectively? 23. Define Receiver sensitivity? 24. What type of optical amplifier EDFA or SOA is used in a CATV system? 1. Draw the basic block diagram of an optical communication link and explain the function of the various parts 2. Discuss on the principal of light transmission in a fiber 3. Draw the electric circuit of an LED & Explain the function of each component? 4. What are the different light sources available? Explain any one of them 5. Write short notes on i) Surface emitting LED ii) Edge emitting LED 6. Explain about Coherent optic system With block diagram

4 UNIT III - 1G Optical Networks 1. What does the acronym SONET stand for? What is the SONET? 2. Define SONET/SDH? 3. What are the benefits of using SONET/SDH system? 4. Define SONET Multiplexing? 5. What are the elements used in SONET/SDH system? 6. What topologies and components are used in SONET network? 7. Why a ring topology is considered reliable? 8. What are the networks used in data communication system? Describe the function of these networks? 9. Define MAN? 10. Draw the functional block diagram of SONET/SDH system? 11. Define STS-1 Signal? 12. Define OC-N signal? 13. Draw the STS-1 signal frame structure? 14. What is meant by saying an overhead and payload are in frame format for transmitted data? 15. Define overhead? 16. Define Transport Overhead (TOH)? 17. Define synchronous payload envelope (SPE)? 18. What is the function of TOH? 19. What is the function of SPE? 20. What is the data rate of STS-1 Signal? 21. What is the next OC signal after OC-192? What is its bit rate? 22. Calculate the data rate of STS-3 Signal (duration of the frame=125microsec) 23. Name the SONET layers 24. Define SONET physical layer? 25. What is the function of section layer? 26. What is the function of line layer? 27. Define path layer? 28. What is meant by byte interleaving multiplexer? 29. What is the function of SONET Regenerator? 30. Define Add/Drop Multiplexer? 31. Define WDM? 32. Why do we need to develop WDM fiber optic network? 33. Why is WDM the major trend in Fiber optic network? 1. Explain the functional block diagram of the SONET/SDH Multiplexing? 2. Briefly describe the functions, service of the SONET layer 3. Explain the elements of SONET/SDH infrastructure?

5 4. Describe how a ULSR network restores traffic 5. Describe how a BPSR network restores traffic 6. Explain about MAN with Layered Architecture UNIT IV - Broadcast And Select Networks 1. Define Topologies? 2. Define Broadcast and select Network? 3. Define Broadcast and select single hop network? 4. Define Multihop network? 5. What are the characteristics of single hop network? What are the types of topologies used in data communication network? 6. Draw the block diagram of the broadcast and select WDM network? 7. What are the topologies used in broadcast network and select network? 8. Define an N*N star coupler? 9. What is need for passive star topology? 10. Define: Bus topology & Tree topology? 11. What is the Difference between passive star topology and linear bus topology? 12. What are the characteristics used in single hop network? 13. What is the difference between single hop system and multihop system? 14. Define MAC protocol? 15. What is meant by synchronization? 16. Define Slotted ALOHA? 17. Why do cable network operators are interested in new architecture(such as FTTC, FTTH) 18. Define FTTC 19. Why a CATV system is called HFC? 20. In CATV, a coaxial cable is used only for the short connection between an optical receiver node & your TV set. Why is this still necessary? 21. How does access network provide broadband access from the customers premises to the edge network? 22. Give some applications of broadcast and select technique 1. Explain the topologies of broadcast networks 2. Explain the Broadcast and select single hop network? 3. Explain the Broadcast and select multihop network? 4. Explain the characteristics of single hop network? 5. Explain the elements of optical access network architecture? 6. Describe Slotted ALOHA protocol? 7. Explain the future access networks

6 8. Explain about MAC Protocol 9. Short notes on: i) FTTC & FTTH ii) ISDN & HFC UNIT V - Wavelength Routed Networks & Optical TDM and CDM Networks 1. What are the two disadvantages of broadcast & select networks when its used in WAN 2. Which fiber optic networks belong to the first generation &which one belongs to the second generation? Give E.g. 3. What are the advantages of wavelength routed network? 4. Why do we need Optical Cross Connect (OCC)? 5. How to measure the benefits of wavelength conversion? 6. Why do we need an optical layer? 7. What services does an optical layer provide to the layer above? 8. Describe the optical layer service termed establishing light path 9. Describe the optical layer service termed establishing virtual circuits 10. Show the layered structure of fiber optic network, including the optical layer 11. Define OTDM? 12. Define Spread Spectrum? 13. What are spread spectrum techniques used CDMA? 14. Define Frequency Hopping Spread Spectrum? 15. Define Direct Sequence Spread Spectrum? 1. Explain OFDM 2. Explain Optical Cross Connect 3. Explain OCDMA network 4. Explain Spread Spectrum techniques? 5. Show the layered structure of fiber optic network & Describe their major functions

Optical Networks: A Practical Perspective

Optical Networks: A Practical Perspective Rajiv Ramaswami Tellabs, Inc. Kumar N. Sivarajan Indian Institute of Science 14 Morgan Kaufmann Publishers, Inc. San Francisco, California Contents Foreword vii