1. CS2403 DIGITAL SIGNAL PROCESSING TECHNICAL QUIZ - I

2. 1. Which domain a signal can represent? (a) Time domain (b) frequency domain (c) both (a) and (b) (d) none of these

3. 2. In which biasing condition both LEDs and ILDs operates correctly? a. Forward bias b. Reverse bias c. Neither A or B d. Either A or B

4. 3. Which of the following is a Single-frequency light? a. Pure b. Intense c. Coherent d. Monochromatic

5. 4. Why Laser light is very bright? a. Pure b. White c. Coherent d. Monochromatic

6. 5. Which of the following is NOT a common light detector? a.PIN photodiode b.Photovoltaic diode c. Photodiode d. Avalanche photodiode

7. 6. Which fiber-optic system is better? a. 3 repeaters b. 8 repeaters c. 11 repeaters d. 20 repeaters

8. 7. What are all the important requirements for successful transmission system using light? a.Powerful, reliable light source b.Strong glass c.Reliable, high cost transmission medium d. Powerful regenerators

9. 8. What is used to block light from a laser? a.Neutral density b.Color c. Interference d.Spatial

10. 9. What type of light can be a coherent? a.Spontaneous emission b. Monochromatic and in-phase c. Narrow beam divergence d. Monochromatic

11. 10. What is important for Coherence of laser light? a.Light propagation b. Getting laser light to pass through air c. Drilling holes d. Holography

12. 11. How much percentage purity is required for manufacturing ultrapure glass? a.99.9 % b. 99.99 % c. 99.999 % d. 99.9999 %

13. 12. How many longitudinal modes can fall within a laser’s gain bandwidth? a.2 b. 5 c. 9 d. No fixed limit, dependent on bandwidth and mode spacing

14. 13. What parameter of light detector determines the range or system length that can be achieved for a given wavelength? a. Transit time b. Spectral response c. Dark current d. Responsitivity

15. 14. What are the causes for Dark current in light detectors? a.Thermally generated carriers in the diode b. The absence of light input c. Small leakage current d. Its imperfection

16. 15. What is the unit of responsitivity? a.Ampere/volt b. Ampere/watt c. Watt/ampere d. Volts/ampere

17. 16. Which of the following is not a characteristic of light detectors? a.Responsivity b. Spectral response c. Transmit time d. Dispersion

18. 17. What is the energy of the photon? a.Directly proportional to its bandwidth b. Directly proportional to Planck’s constant c. Directly proportional to Boltzmann’s constant d. Inversely proportional to the Planck’s constant

19. 18. Which of the following is a disadvantage for plastic fiber optics? a.Noise immunity b. Electric hazards c. Higher losses d. All of these

20. 19. What is the core diameter(nm) of a single mode optical fiber?. a.0.1 b. 0.01 c. 0.2 d. 0.05

21. 20. Which is not a possible cause of optical fiber loss? a.Impurities b. Glass attenuation c. Stepped index operation d. Microbending

22. 21. What is meant by fiber splicing? a.Fusion b. Butt c. Glue d. Both fusion and butt

23. 22. What is higher-order mode in fiber optics? a.Cladding boundary at high angle b. Backscattering electromagnetic signals c. Diffracting signals d. All of these

24. 23. Which of the following does not causes light attenuation in fiber optics? a.Backscattering b. Absorption c. Refraction d. Microbends

25. 24. Why are visible-light LEDs not used for fiber optics? a. It has high losses b. It has short wave c. It has low attenuation d. It has weak signal

26. 25. What is the core diameter of single mode step index fibre ? a. 60 to 70 µm b. 50 to 200 µm c. 100 to 250 µm d. 8 to 10 µm

27. 26. How the light rays will travel in different parts of the multimode graded index fiber? a.at different speeds b. both a and b c. with same speed d. none of the above

28. 27. What is the major loss that occurs in optical fiber? a.Scattering b.Absorption c.Macrobending d.All the above

29. 28. What is the another name for dispersion? a.Modal b.Chromatic c.Polarization mode d.All the above

30. 29. Which dispersion occurence in fiber cable, will cause a portion of the light energy to travel in the cladding? a.Modal dispersion b. Cable dispersion c.Waveguide dispersion d.Material dispersion

31. 30. Which technique is used to minimize the pulse dispersion effect ? a. Use a higher frequency light source b. Use plastic cladding c. Minimize the core diameter d. All the above

32. 31. Which parameter square root will be equal to the refractive index of materials? a. electrical permittivity b. magnetic permeability c. electrical permittivity x magnetic permeability d. None

33. 32. Light may be propagated along a fiber-optic cable in which of the following modes? a.multimode step index b. single-mode step index c. multimode graded index d. all of the above

34. 33. In order for a light ray to propagate along a fiber-optic cable, what must the relationship be between the angle of incidence and the critical angle? a.θ i > θ c b. θ i < θ c c. θ i = θ c d. none of the above

35. 34. Which of the following is the fastest light sensor? a.PIN photodiode b. Photovoltaic diode c. Phototransistor d. Avalanche photodiode

36. 35. Which fiber-optic cable is widely used at short to medium distances, is easiest to make, and is the least expensive? a.step index b. graded index c. multimode graded index d. multimode step index

37. 36. What is the new and better way to deal with dispersion that uses equalization techniques to adjust the received waveform to compensate for dispersion? a. electronic dispersion compensation b. chromatic dispersion c. polarization mode dispersion d. multimode graded dispersion

38. 37. Which of the following is not one of the most important specifications of a fiber-optic cable? a.size b. attenuation c. cladding d. bandwidth

39. 38. Which of the following terms refers to how light energy is converted to heat in the fiber- optic core material because of the impurity of glass or plastic? a.dispersion b. scattering c. attenuation d. absorption

40. 39. In a fiber-optic cable, what determines the maximum speed of the data pulses the cable can handle? a. absorption b. attenuation c. Bandwidth d. cladding

41. 40. How to represent cable attenuation? a. Loss per foot b. dB/km c. intensity per mile d. voltage drop per inch

42. 41. Why are visible-light LEDs not used for fiber optics? a.It has high losses b. It has short wave c. It has low attenuation d. It has weak signal

43. 42. Which of the following is not a solid-state optical detector? a. APD b. PIN c. PMT d. Phototransistors

44. 43. Which of the following statement is correct? a. Optical detectors respond to Intensity b. Optical detectors respond Light c. Optical detectors respond Density d. Optical detectors respond Photon

45. 44. Which optical detector is used when high sensitivity and bandwidth are required? a.PMT b. APD c. PIN d. Phototransistor

46. 45. What is the average loss in fiber splice? a.0.10 dB b. 0.15 dB c. 0.20 Db d. 0.25 dB

47. 46. What is the range of mechanical splicing attenuation loss (dB)? a.0.1 b. 0.01 c. 0.001 d. 1

48. 47. How to protect core and cladding of the fiber? a.Insulation b. Fiber insulation c. Silica d. Polymer jacket

49. 48. What type of device is an optical splitter? a. Active b. Passive c. normal d. none of the above

50. 49. Which is not a possible cause of optical fiber loss? a. Impurities b. Glass attenuation c. Stepped index operation d. Micro bending

51. 50. What causes the spreading of the light pulse as it travels along the fiber? a. Pulse distortion b. Pulse absorption c. Pulse emission d. Pulse conduction