PARISUTHAM INSTITUTE OF TECHNOLOGY AND SCIENCE
Department of ECE
AY 2015-16
IV Year /VII Sem.
QUIZ-1
EC2402 – Optical Communication & Networking
1. Which of the following is not a factor in cable light loss?
a. Reflection
c. Scattering
b. Absorption
d. Dispersion
ANS: a
2. In which biasing condition both LEDs and ILDs operates correctly?
a. Forward bias
c. Neither A or B
b. Reverse bias
d. Either A or B
3. Which of the following is a Single-frequency light?
a. Pure
c. Coherent
b. Intense
d. Monochromatic
4. Why Laser light is very bright?
a. Pure
b. White
ANS: d
c. Coherent
d. Monochromatic
5. Which of the following is NOT a common light detector?
a. PIN photodiode
c. Photodiode
b. Photovoltaic diode
d. Avalanche photodiode
6. Which fiber-optic system is better?
a. 3 repeaters
b. 8 repeaters
c. 11 repeaters
d. 20 repeaters
ANS: a
ANS: c
ANS: b
ANS: a
7. What are all the important requirements for successful transmission system using light?
a. Powerful, reliable light source
c. Reliable, high cost transmission medium ANS: a
b. Strong glass
d. Powerful regenerators
8. What is used to block light from a laser?
a. Neutral density
c. Interference
b. Color
d. Spatial
ANS: c
9. What type of light can be a coherent?
a. Spontaneous emission
c. Narrow beam divergence
b. Monochromatic and in-phase
d. Monochromatic
ANS: b
10. What is important for Coherence of laser light?
a. Light propagation
c. Drilling holes
b. Getting laser light to pass through air
d. Holography
ANS: d
11. How much percentage purity is required for manufacturing ultrapure glass?
a. 99.9 %
c. 99.999 %
ANS: d
b. 99.99 %
d. 99.9999 %
12. How many longitudinal modes can fall within a laser’s gain bandwidth?
a. 2
c. 9
ANS: d
b. 5
d. 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
c. Dark current
ANS: b
b. Spectral response
d. Responsitivity
14. What are the causes for Dark current in light detectors?
a. Thermally generated carriers in the diode c. Small leakage current
b. The absence of light input
d. Its imperfection
15. What is the unit of responsitivity?
a. Ampere/volt
b. Ampere/watt
c. Watt/ampere
d. Volts/ampere
16. Which of the following is not a characteristic of light detectors?
a. Responsivity
c. Transmit time
b. Spectral response
d. Dispersion
ANS: a
ANS: b
ANS: d
17. What is the energy of the photon?
ANS: b
a. Directly proportional to its bandwidth
c. Directly proportional to Boltzmann’s
constant b. Directly proportional to Planck’s constant
d. Inversely proportional to
the Planck’s constant
18. Which of the following is a disadvantage for plastic fiber optics?
a. Noise immunity
c. Higher losses
b. Electric hazards
d. All of these
ANS: c
19. What is the core diameter(nm) of a single mode optical fiber?.
a. 0.1
c. 0.2
b. 0.01
d. 0.05
ANS: b
20. Which is not a possible cause of optical fiber loss?
a. Impurities
c. Stepped index operation
b. Glass attenuation
d. Microbending
ANS: c
21. What is meant by fiber splicing?
a. Fusion
b. Butt
c. Glue
ANS: d
d. Both fusion and butt
22. What is higher-order mode in fiber optics?
a. Cladding boundary at high angle
c. Diffracting signals
b. Backscattering electromagnetic signals d. All of these
ANS: a
23. Which of the following does not causes light attenuation in fiber optics?
a. Backscattering
c. Refraction
ANS: c
b. Absorption
d. Microbends
24. Why are visible-light LEDs not used for fiber optics?
a. It has high losses
c. It has low attenuation
b. It has short wave
d. It has weak signal
25. What is the core diameter of single mode step index fibre ?
a. 60 to 70 µm
c. 100 to 250 µm
b. 50 to 200 µm
d. 8 to 10 µm
ANS: a
ANS: d
26. How the light rays will travel in different parts of the multimode graded index fiber?
a. at different speeds
c. with same speed
ANS: a
b. both a and b
d. none of the above
27. What is the major loss that occurs in optical fiber?
a.Scattering
b.Absorption
c.Macrobending
d.All the above
ANS: d
28. What is the another name for dispersion?
a.Modal
c.Polarization mode
ANS: d
b.Chromatic
d.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
c.Waveguide dispersion
ANS: b
b. Cable dispersion
d.Material dispersion
30. Which technique is used to minimize the pulse dispersion effect ?
a. Use a higher frequency light source
c. Minimize the core diameter
b. Use plastic cladding
d. All the above
ANS: c
31. Which parameter square root will be equal to the refractive index of materials? ANS: a
a. electrical permittivity
c. electrical permittivity x magnetic permeability
b. magnetic permeability
d. None
32. Light may be propagated along a fiber-optic cable in which of the following modes?
a. multimode step index
c. multimode graded index
ANS: d
b. single-mode step index
d. 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
c. θi = θc
ANS: a
b. θi < θc
d. none of the above
34. Which of the following is the fastest light sensor?
a. PIN photodiode
c. Phototransistor
b. Photovoltaic diode
d. Avalanche photodiode
ANS: d
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
c. multimode graded index ANS: a
b. graded index
d. 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?
ANS: d
a. electronic dispersion compensation
c. polarization mode dispersion
b. chromatic 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
c. cladding
ANS: a
b. attenuation
d. bandwidth
38. Which of the following terms refers to how light energy is converted to heat in the fiberoptic core material because of the impurity of glass or plastic?
a. dispersion
c. attenuation
ANS: d
b. scattering
d. absorption
39. In a fiber-optic cable, what determines the maximum speed of the data pulses the cable
can handle?
a. absorption
c. Bandwidth
ANS: c
b. attenuation
d. cladding
40. How to represent cable attenuation?
a. Loss per foot
b. dB/km
c. intensity per mile
d. voltage drop per inch
ANS: b
41. Why are visible-light LEDs not used for fiber optics?
a. It has high losses
c. It has low attenuation
b. It has short wave
d. It has weak signal
ANS: a
42. Which of the following is not a solid-state optical detector?
a. APD
c. PMT
b. PIN
d. Phototransistors
ANS: c
43. Which of the following statement is correct?
a. Optical detectors respond to Intensity
b. Optical detectors respond Light
ANS: a
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
c. PIN
ANS: a
b. APD
d. Phototransistor
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
ANS: b
46. What is the range of mechanical splicing attenuation loss (dB)?
a. 0.1
c. 0.001
b. 0.01
d. 1
ANS: a
47. How to protect core and cladding of the fiber?
a. Insulation
c. Silica
b. Fiber insulation
d. Polymer jacket
ANS: d
48. What type of device is an optical splitter?
a. Active
c. normal
b. Passive
d. none of the above
ANS: b
49. Which is not a possible cause of optical fiber loss?
a. Impurities
c. Stepped index operation
b. Glass attenuation
d. Micro bending
ANS: c
50. What causes the spreading of the light pulse as it travels along the fiber?
a. Pulse distortion
c. Pulse emission
b. Pulse absorption
d. Pulse conduction
ANS: a
Faculty Sign:
Faculty Name: S.SHANMUGA PRIYA
HOD Signature