OFC 3rd unit

1. What is the function of optical source?
2. Define electroluminescence phenomena.
3. What are the main types of optical light sources?
4. Name some optical sources.
5. Define intrinsic material.
6. Name some non semiconductor laser devices used in optical fiber communication.
7. What is stimulated absorption?
8. What are the different methods of emission process?
9. Give the draw backs of LED’s over injection Laser.
10. What are the advantages of LED?
11. Define internal quantum efficiency.
12. Give the formula for the optical power generated internally by the LED.
13. Define confinement factor.
14. Write the formula for non radiative minority carrier life time.
15. What are the main causes of optical loss in LED?
16. State law of Brightness.
17. Define emission response time.
18. Name two basic LED configurations used for fiber optic communication.
19. What are the other names for Surface emitter?
20. Give some examples of ternary alloy.
21. What are the characteristics of LED?
22. Define lasing.
23. Give some examples of quaternary alloy.
24. Define external quantum efficiency.
25. What are the mechanisms to determine the modulation bandwidth of LED?
26. Why laser is preferred over LED?
27. Define population inversion.
28. Give the condition for lasing.
29. Name the different types of LED structures.
30. Name the different types of LASER modes.
31. What are the advantages of injection laser over other semiconductor laser?
32. What is the condition for stimulated emission?
33. Define the modulation bandwidth of LED.
34. What are the applications of LED.
35. What are the techniques used to reduce threshold current in Laser diodes?
36. What are the causes for nonlinearity in optical source?
37. What are the requirements of photo detector?
38. What are the characteristics of silicon photo detector?
39. Name two devices used as photo detectors.
40. Define quantum efficiency of a photo detector.
41. Define responsivity of a photo detector
42. What are the characteristics of photo detectors?
43. Define ionization rate.
44. Write down the formula for long wavelength cutoff.
45. What is meant by impact ionization of APD?
46. Define O/P S/N ratio of optical receiver.
47. What are the conditions to achieve a high signal – to – noise ratio?
48. What are the factors to limit the speed of response of a photodiode?
49. Name the three main noise currents in photo detectors.
50. Draw the simple model of a photo detector receiver.
51. Define quantum noise.
52. Define photodiode dark current.
53. Draw the equivalent circuit for photo detector receiver circuit.
54. Define multiplication factor.
55. What are the important parameters which describe the noise performance of a photo conductor?
56. Write the formula for transit time.
57. Define flicker noise.
58. What factors decide the detectors response time?
59. Bring out comparisons between direct and indirect band gaps.
60. Define lambertain pattern.
61. Why optical confinement is considered one of the most important in LED?
62. What is the band gap of ternary and quaternary alloy?
63. What are the factors that determine the modulation bandwidth of an LED?
64. Draw the structure of high – radiance surface – emitting LED.
65. Why direct band gap materials are used for light source?
66. Give the formula for internal quantum efficiency of optical source.
67. Give the formula for bulk recombination life time.
68. Draw figure for stimulated emission.
69. Give the formula for 3 – dB modulation bandwidth and life time reduction.
70. Why mirror facets are used in Fabry – Perot resonator laser diode?
71. What is the response time of a laser diode?
72. How does lasing action is obtained in distributed – feedback laser?
73. Define modes of a cavity.
74. Draw the structure of a distributed – feedback laser diode.
75. Give the relationship between gain and frequency.
76. Give the formula for frequency spacing and wavelength spacing.
77. Give the condition when the cavity resonates.
78. Give the formula for power – bandwidth product.
79. Which factor effects the frequency response of a LED?
80. Define diffusion length.
81. Draw reach – through avalanche photodiode structure..
82. Define minimum detectable optical power.
83. What is bulk dark current?
84. Give the formula for responsivity of APD.
85. Write the formula for noise figure.