Thursday, 7 September 2017

200 OPTICAL ELECTRONICS INTERVIEW QUESTIONS

By Ask Biomedical
*Interview questions on OPTICAL*

  1. State Faraday’s rotation law. 
  2.  State the properties of S matrix. 
  3. What are the reasons that low frequency parameters cannot be Measured in 
  4. microwaves? 
  5. 4. State the two parameters that describe a directional coupler? Define them. 
  6. 5. State TEE junction theorems. 
  7. 6. What is S matrix and write the S matrix of N port network? 
  8. 7. What is meant by hybrid coupler? 
  9. 8. Compare z parameters and ABCD parameters with S-parameters. 
  10. 9. What are hybrid rings? 
  11. 10.List the parameters that determine the performance of a directional coupler. 
  12. 11. Explain the action of a rat-race junction. 
  13. 12.Why are waveguide bends and twists constructed so that the direction of 
  14. propagated energy is 
  15. gradually changed? 
  16. 1.Define GUNN effect. 
  17. 2. What is the necessary condition for an IMPATT to produce oscillations? 
  18. 3. List the differences between microwave transistor and TED devices. 
  19. 4. What are the advantages and disadvantages of parametric amplifier? 
  20. 5. What is meant by avalanche transit time device? 
  21. 6. Discuss the applications of PIN diode. 
  22. 7. What is a parametric amplifier? How is it different from a normal amplifier? 
  23. 8. What is the theory of a negative resistance amplifier? 
  24. 9. Explain how a tunnel diode can be used as a amplifier. 
  25. 10.List the several donation formation modes of a Gunn diode. 
  26. 11.State the performance characteristics of IMPATT and TRAPATT diode. 
  27. 12. An IMPATT diode has a drift length of 2 µm. Determine the operating 
  28. frequency of IMPATT diode if the drift velocity for Si is 107 cms/sec 
  29. 1. Draw the electronic admittance diagram of reflex klystron. 
  30. 2. State the differences between TWT and klystron? 
  31. 3. Can a two cavity klystron amplifier be used an oscillator? If yes, how? 
  32. 4. What is the purpose of slow wave structures in TWT? 
  33. 5. What is meant by frequency pushing and frequency pulling?. 
  34. 6. What is velocity modulation? 
  35. 7. What are the limitations of conventional tubes at microwave 
  36. frequencies?Explain how these 
  37. limitations can be overcome.
  38. 8. What are the performance characteristics of a Klystron amplifier? 
  39. 9. How is bunching achieved in a cavity magnetron? 
  40. 10. What are cross field deices? 
  41. 11. How is tuning achieved in reflex klystron oscillators? 
  42. 12. What is strapping in magnetron? How is the same effect obtained without 
  43. strapping? 
  44. 1. What are the advantages of microstrip line over strip line? 
  45. 2. What are the advantages of MMIC over discrete circuit? 
  46. 3. What are the properties of dielectric materials? 
  47. 4. What are the losses in strip lines? 
  48. 5. List the various MMIC fabrication techniques. 
  49. 6. Microstrip line is also called an open strip line.Comment on this. 
  50. 7. Why is it difficult to establish microstrip short circuits? 
  51. 8. What are the design considerations for a microstrip line? 
  52. 9. Why are propagating modes along the strip lines are non-TEM and not pure 
  53. TEM modes? 
  54. 10.How are waveguides different from normal two – wire transmission lines? 
  55. 11.Give the physical interpretation for phase and group velocity in relation to 
  56. speed of light. 
  57. 1. What is Bolometer? Give two examples? 
  58. 2. A wave guide load is used to absorb power of 2W., reflected power is 
  59. 3mW.Find magnitude of 
  60. VSWR. 
  61. 3. Why reflex klystron is a square wave 1kHz PAM while microwave 
  62. measurements are done using 
  63. VSWR? 
  64. 4. What are the sources of error in return loss measurement using a waveguide 
  65. reflectometer and 
  66. klystron source? 
  67. 5. What is meant by duty cycle? 
  68. 6. How are microwave measurements different from low frequency 
  69. measurements? 
  70. 7. List the various techniques of measuring unknown frequency of a microwave 
  71. generator. 
  72. 8. How can you extend the range of power measurement? 
  73. 9. Describe how an ordinary voltmeter can be calibrated to VSWR directly.What 
  74. are the drawbacks 
  75. of such a VSWR meter? 
  76. 10. List any two methods of measuring impedance of a terminating load in a 
  77. microwave system. 
  78. 11. Explain the concept of double minimum method of measuring VSWR.
  79. 1. Among Microwaves and light waves which have high bit rate distance 
  80. product?Why? 
  81. 2. Mention the three advantages of optical fiber as waveguide over conventional 
  82. metallic waveguide? 
  83. 3. What is meant by mode and index profile? 
  84. 4. Mention the advantages of Graded Index fiber. 
  85. 5. Write the expression for the refractive index in Graded index fiber. 
  86. 6. Define Numerical Aperture of step index fiber. 
  87. 7. Give the expression of the effective number of modes that are guided by a 
  88. curved 
  89. multimode fiber of radius ‘ a’. 
  90. 8. State Snells Law. 
  91. 9. Define Critical angle? 
  92. 10. Define TIR? 
  93. 11. What is the need of Cladding? 
  94. 12. Define core index difference. 
  95. 13. Define refractive index? 
  96. 14. What are leaky modes in optical fibers? 
  97. 15. Define External reflection of light rays? 
  98. 16. What is meant by modes of waveguide? 
  99. 17. Define V number? 
  100. 18. What is relation between V number and power flow in cladding? 
  101. 19. What is the fundamental parameter of SM fiber? 
  102. 20. Give the relation between rays and modes? 
  103. 21. What are the advantages and disadvantages of SM fiber? 
  104. 22. What are the advantages and disadvantages of MM fiber? 
  105. 23. Define skew rays and merdional rays? 
  106. 24. Define cutoff conditions? 
  107. 25. What is meant by Degenerate modes? 
  108. 26. What is meant by linearly polarized modes? 
  109. 27. Define MFD? 
  110. 28. Define Bi refrigence and beat length? 
  111. 29. A point source of light is 12cm below the surface of a large body of water 
  112. (n=1.33). 
  113. What is the radius of the largest circle on the water surface through which the 
  114. lights 
  115. can emerge? 
  116. 30. Consider a parabolic index waveguide with n1=1.75,n2=1.677 and core radius 
  117. 52µm. 
  118. Calculate the numerical aperture at the axis and at a point 20µm from the axis. 
  119. 31. Why do we prefer step index single mode fiber for long distance 
  120. communication? 
  121. 32. Why do we use LP01 mode for long distance communications? 
  122. 33. What are three operating windows? 
  123. 34. Alight ray is incident from glass to air. Calculate critical angle?
  124. 1. An optical signal has lost 55% of its power after traversing 3.5 km of fiber. 
  125. What is 
  126. the loss in dB/km of this fiber? 
  127. 2. Define mode-field diameter. 
  128. 3. What are the causes of absorption? 
  129. 4. Define normalized propagation constant. 
  130. 5. List the basic attenuation mechanisms in an optical fiber. 
  131. 6. What is meant be mode coupling ? What causes it ? 
  132. 7. Mention the two causes of intramodal dispersion. 
  133. 8. Define fiber loss. 
  134. 9. What do you mean be polarization mode dispersion? 
  135. 10. Commonly available single mode fibers have beat lengths in the range 10cm 
  136. <Lp 
  137. <2m. What range of refractive index differences does this correspond to? 
  138. 11. Find the coupling loss for two fibers having core refractive index profiles _E 
  139. =2.0 and _R =1.5 
  140. 12. Define Raleigh Scattering loss. 
  141. 13. Define Mie Scattering loss. 
  142. 14. When the mean optical power launched into an 8 km length of fiber is 120 µw. 
  143. Determine the overall signal attenuation or loss in decibels. 
  144. 15. How are micro bending losses reduced? 
  145. 16. Distinguish intrinsic and extrinsic absorption. 
  146. 17. Distinguish dispersion shifted and dispersion flattened fibers. 
  147. 1. Define radiance. 
  148. 2. What is meant by “ population inversion”? 
  149. 3. what is meant by heterojunction? 
  150. 4. What is meant by indirect band gap semiconductor material? 
  151. 5. Draw the three key transition processes involved in laser action. 
  152. 6. Give examples for direct and indirect semiconductor materials. 
  153. 7. Define internal quantum efficiency of an LED. 
  154. 8. Name few splicing methods in fiber optics. 
  155. 9. Compare LED and LASER. 
  156. 10. What so you mean by heterojunction ? Mention its advantages. 
  157. a. List the different types of mechanical misalignments that can occur between 
  158. two joined fibers. 
  159. b. Calculate the ratio of stimulated emission rata to the spontaneous emission 
  160. rate for a lamp operating at a temperature of 1000 K. Assume average 
  161. operating wavelength is 0.5µm. 
  162. 11. Define lambertian pattern . 
  163. 12. Define FWHM. 
  164. 13. Define Modal or speckle noise. 
  165. 14. Define “ Kinks”. 
  166. 15. Define Mode partition noise.
  167. 16. Define Lensing Schemes. 
  168. 17. Define Splicing ? What are types of Splicing.? 
  169. 18. What are the Characteristics of Light Source . 
  170. 1. Define diffusion length. 
  171. 2. Define avalanche effect . 
  172. 3. Define responsivity. 
  173. 4. Define Quantum efficiency of photo detector. 
  174. 5. Write the noise sources in the receiver section. 
  175. 6.Define Quantum limit. 
  176. 7.What are the desired features of photo detector. 
  177. 8.A photo diode is constructed of GaAs which has a bandgap energy of 1.43Ev 
  178. at 300k. 
  179. What is meant by long wavelength cutoff? 
  180. 9.What are the benefits of trans impedance amplifier. 
  181. 10.Define long wave length cutoff related photo diode. 
  182. 11.What is meant by bulk dark current? 
  183. 12.A photo diode has a capacitance of 6pf.Calculate the max load resistance 
  184. which allows 
  185. an 8MHz post defection BW. 
  186. 13. What is meant by impact ionization. In APD? 
  187. 14.What is transit time of photo carriers? 
  188. 15.What is meant by ionization rate? 
  189. 16. Define avalanche multiplication? 
  190. 17.Define S/N ratio of an optical receiver?What are the conditions are required 
  191. to achieve high S/N? 
  192. 18.Define BER? 
  193. 19.Define Extinction ratio? 
  194. 20. Define photo current? 
  195. 21. What is p+ _pn+ reach through structure? 
  196. 22.Define excess noise factor? 
  197. 23. What is meant by Pre amplifier? What are the advantages of pre amplifier? 
  198. 24.Whar are the draw backs of high impedance amplifier? 
  199. 1. List out the requirements that are to be considered in analyzing a link 
  200. 2. Differentiate link power budget and rise time budget. 
  201. 3. What is SONET? How does it differ from SDH? 
  202. 4. What are solitons? 
  203. 5. What is meant by ‘modal noise’?

0 comments:

Post a Comment