CS2403

DIGITAL SIGNAL PROCESSING

TECHNICAL QUIZ - I

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

2. In which biasing condition both LEDs and ILDs operates correctly?

a. Forward bias b. Reverse biasc. Neither A or Bd. Either A or B

3. Which of the following is a Single-frequency light?

a. Pure b. Intense c. Coherent d. Monochromatic

4. Why Laser light is very bright?

a. Pure b. Whitec. Coherent d. Monochromatic

5. Which of the following is NOT a common light detector?

a. PIN photodiode b.Photovoltaic diode c. Photodioded. Avalanche photodiode

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

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 mediumd. Powerful regenerators

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

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

10. What is important for Coherence of laser light?

a. Light propagation b. Getting laser light to pass through air c. Drilling holesd. Holography

11. How much percentage purity is required for manufacturing ultrapure glass?

a. 99.9 % b. 99.99 % c. 99.999 %d. 99.9999 %

12. How many longitudinal modes can fall within a laser’s gain bandwidth?

a. 2 b. 5 c. 9d. No fixed limit, dependent on bandwidth and

mode spacing

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 responsec. Dark current d. Responsitivity

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 currentd. Its imperfection

15. What is the unit of responsitivity?a. Ampere/voltb. Ampere/watt c. Watt/ampered. Volts/ampere

16. Which of the following is not a characteristic of light detectors?

a. Responsivity b. Spectral response c. Transmit timed. Dispersion

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 constantd. Inversely proportional to the Planck’s

constant

18. Which of the following is a disadvantage for plastic fiber optics?

a. Noise immunity b. Electric hazards c. Higher lossesd. All of these

19. What is the core diameter(nm) of a single mode optical fiber?.

a. 0.1 b. 0.01 c. 0.2d. 0.05

20. Which is not a possible cause of optical fiber loss?

a. Impurities b. Glass attenuation c. Stepped index operationd. Microbending

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

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

23. Which of the following does not causes light attenuation in fiber optics?

a. Backscattering b. Absorption c. Refractiond. Microbends

24. Why are visible-light LEDs not used for fiber optics?

a. It has high lossesb. It has short wave c. It has low attenuationd. It has weak signal

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 µmd. 8 to 10 µm

26. How the light rays will travel in different parts of the multimode graded index fiber?

a. at different speedsb. both a and bc. with same speedd. none of the above

27. What is the major loss that occurs in optical fiber?

a.Scatteringb.Absorptionc.Macrobendingd.All the above

28. What is the another name for dispersion?a.Modalb.Chromaticc.Polarization moded.All the above

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 dispersiond.Material dispersion

30. Which technique is used to minimize the pulse dispersion effect ?

a. Use a higher frequency light sourceb. Use plastic cladding c. Minimize the core diameterd. All the above

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 permeabilityd. None

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 indexd. all of the above

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. θi > θc

b. θi < θc

c. θi = θc

d. none of the above

34. Which of the following is the fastest light sensor?

a. PIN photodiode b. Photovoltaic diode c. Phototransistord. Avalanche photodiode

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 indexc. multimode graded indexd. multimode step index

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 compensationb. chromatic dispersionc. polarization mode dispersion d. multimode graded dispersion

37. Which of the following is not one of the most important specifications of a fiber-optic cable?

a. size b. attenuationc. claddingd. bandwidth

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. dispersionb. scattering c. attenuationd. absorption

39. In a fiber-optic cable, what determines the maximum speed of the data pulses the cable can handle?

a. absorption b. attenuationc. Bandwidthd. cladding

40. How to represent cable attenuation? a. Loss per footb. dB/km c. intensity per miled. voltage drop per inch

41. Why are visible-light LEDs not used for fiber optics?

a. It has high lossesb. It has short wave c. It has low attenuationd. It has weak signal

42. Which of the following is not a solid-state optical detector?

a. APD b. PIN c. PMTd. Phototransistors

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

44. Which optical detector is used when high sensitivity and bandwidth are required?

a. PMT b. APD c. PINd. Phototransistor

45. What is the average loss in fiber splice?a. 0.10 dBb. 0.15 dB c. 0.20 Dbd. 0.25 dB

46. What is the range of mechanical splicing attenuation loss (dB)?

a. 0.1 b. 0.01 c. 0.001d. 1

47. How to protect core and cladding of the fiber?

a. Insulation b. Fiber insulation c. Silicad. Polymer jacket

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

49. Which is not a possible cause of optical fiber loss?

a. Impurities b. Glass attenuation c. Stepped index operation d. Micro bending

50. What causes the spreading of the light pulse as it travels along the fiber?

a. Pulse distortion b. Pulse absorption c. Pulse emissiond. Pulse conduction