S.R.M. UniversityFaculty of Engineering and TechnologySchool of Electronics and Communication Engineering

Question BankSubject Code : EC459Subject Name : Optical NetworksClass : IV Year B.Tech (ECE)

Unit – I – Fiber and Network ComponentsPart – 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 = 0.200 and n1 = 1.486. Evaluate pulse spreading per 1 km length.15. Consider the model dispersion for a step index multimode fiber NA=0.200 and n1=1.486. 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=1.4468.17. 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.

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 Phenomenon28. 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 WDM33. 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 EDFA41. What is the function of coupler?42. Name and describe two major classes of filters43. What are the basic characteristics of a filter?44. Give examples of reciprocal and nonreciprocal devices45. Explain the function of circulators and isolators.

PART B

1. List the major Causes of Attenuation in an optical fiber & explain their mechanism2. Explain in detail about light propagation in a fiber?3. List three major causes of dispersion in an optical fiber & Explain their mechanism4. Explain the principle of operation of a semiconductor optical amplifier (SOA)?5. Show the structure of an EDFA & Explain the function of each component6. Explain how stimulation emission occurs in an EDFA7. What is the function & the principle of operation of an isolator? Give Eg. Of isolator Applications8. What is the function & the principle of operation of operation of a circulator? Give E.g. Of its application9. Explain the function of Optical switches10. Explain about Nonlinearity effects in a fiber11. 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?

UNIT II - Modulation, Demodulation & Design Consideration

PART A

1. Define Optical Sources2. Show the diagram of fiber optic communication system3. Draw the block diagram of Optical Transmitter?4. Draw the block diagram of Optical Receiver5. 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 Sources12. 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?

PART B

1. Draw the basic block diagram of an optical communication link and explain the function of the various parts2. Discuss on the principal of light transmission in a fiber3. 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 them5. Write short notes on i) Surface emitting LED ii) Edge emitting LED6. Explain about Coherent optic system With block diagram

UNIT III - 1G Optical NetworksPART A

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?

PART B

1. Explain the functional block diagram of the SONET/SDH Multiplexing?2. Briefly describe the functions, service of the SONET layer3. Explain the elements of SONET/SDH infrastructure?4. Describe how a ULSR network restores traffic5. Describe how a BPSR network restores traffic

6. Explain about MAN with Layered ArchitectureUNIT IV - Broadcast And Select NetworksPART A

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 FTTC19. 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

PART B

1. Explain the topologies of broadcast networks2. 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 8. Explain about MAC Protocol9. Short notes on: i) FTTC & FTTH ii) ISDN & HFC

UNIT V - Wavelength Routed Networks & Optical TDM and CDM Networks

PART A

1. What are the two disadvantages of broadcast & select networks when its used in WAN2. 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 layer11. 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?

PART B

1. Explain OFDM2. 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