Upwork Electronics

Fiber Optics Test 2016

1. For a step index fiber, relationship between numerical aperture (NA) and coupling efficiency (ηc) is ________.

Answers:

  1. a
  2. b
  3. c
  4. d

2. Mirrors are placed in LASER optical sources to maintain conditions for ________.

Answers:

  1. incoherence
  2. amplification
  3. modulation
  4. coherence

3. Optical bandwidth (OB) relates to electrical bandwidth (EB) when

Answers:

  1. OB<EB
  2. OB=EB
  3. OB>EB
  4. OB≥EB

4. What is the thermal noise current it in a resistor R expressed in its mean square value?

where, K is Boltzmann’s constant, T is absolute temperature and B is the bandwidth

Answers:

  1. a
  2. b
  3. c<>
  4. d

5. For a profile parameter (α)=1, the profile shape of refractive index for a graded index fiber will be _______.

Answers:

  1. triangular
  2. parabolic
  3. step
  4. circular

6. The rays which travel in a helical path through an optical fiber are called ______.

Answers:

  1. refracted rays
  2. reflected rays
  3. infra-red rays
  4. skew rays

7. Dark spot defects (DSD’s) occur in:

Answers:

  1. Non-semiconductor LASER
  2. Fiber LASER
  3. Glass fiber LASER
  4. Injection LASER

8. What happens when dispersion occurs?

Answers:

  1. Output transmitted pulse broadens
  2. Output transmitted pulse shortens
  3. Output transmitted pulse gets completely eliminated
  4. None of the above

9. Silicon reach through avalanche photodiodes has _______.

Answers:

  1. maximum absorption of photons
  2. maximum absorption of electrons
  3. maximum quantum efficiency
  4. minimum noise

10. The vapor-phase deposition technique is used to produce _______.

Answers:

  1. fiber-rich glasses
  2. silica-rich glasses
  3. oxide-rich glasses
  4. carbonate-rich glasses

11. Scattering losses happen due to:

Answers:

  1. a rise in temperature
  2. imperfections in glass manufacturing process
  3. humidity
  4. bending of fiber

12. Graded-index fibers have:

Answers:

  1. a constant refractive index in the core
  2. a variable refractive index in the cladding
  3. a variable refractive index in the core
  4. None of these

13. Dispersion in optical fibers causes distortion in _______.

Answers:

  1. analog signals only
  2. digital signals only
  3. both analog and digital signals
  4. infra-red signals only

14. The LASER is a/an

Answers:

  1. incoherent device
  2. switching device
  3. threshold device
  4. incandescent device

15. SONET is _________.

Answers:

  1. Scattered optical network
  2. Synchronous optical network
  3. Stable optical network
  4. Silicon optical network

16. In p-i-n photodiodes “i” stands for:

Answers:

  1. Internal
  2. Intrinsic
  3. Impurity
  4. None of the above

17. Dispersion is the lowest in a________.

Answers:

  1. Multimode step-index fiber
  2. Multimode graded-index fiber
  3. Single-mode step-index fiber
  4. Silicon fiber

18. Superluminescent LED’s are preferred because of _______.

Answers:

  1. large spectral linewidth
  2. a directional output beam
  3. low output power
  4. small size

19. Total internal reflection takes place at angles ________.

Answers:

  1. greater than the critical angle
  2. less than the critical angle
  3. equal to the critical angle
  4. None of the above

20. LED is more suitable for analog transmission because of its _______.

Answers:

  1. linearity
  2. bandwidth (spectrum)
  3. modulation property
  4. output power

21. When optical power is incident on the photo detector during the 0 bit period, then the system is said to exhibit _______.

Answers:

  1. a non-zero extinction ratio
  2. a zero extinction ratio
  3. an infinity extinction ratio
  4. an infinity absorption ratio

22. Which of the following is a fiber dispersion measurement method?

Answers:

  1. Time domain measurement
  2. Interferometric method
  3. Refracted near field method
  4. Reflected near field method

23. Germanium photodiodes are generally not preferred in the optical fiber system because of _________.

Answers:

  1. large current gain
  2. large voltage gain
  3. temperature dependence
  4. large dark current

24. Which one of the following is a type of non-linear scattering?

Answers:

  1. Stimulated Raman scattering (SRS)
  2. Rayleigh scattering
  3. Mie scattering
  4. Ultraviolet scattering

25. Refer to the figure above.

The critical angle at the core cladding interface is given by:

Answers:

  1. a
  2. b
  3. c
  4. d

26. Intersymbol interference (ISI) in optical fibers occurs due to ______.

Answers:

  1. refraction
  2. scattering
  3. bending
  4. dispersion

27. Near-field scanning method is used to measure:

Answers:

  1. Fiber attenuation
  2. Fiber dispersion
  3. Fiber numerical aperture
  4. Fiber refractive index profile

28. Which phenomenon does not let light rays escape an optical fiber?

Answers:

  1. Total internal reflection
  2. Total internal refraction
  3. Total internal diffraction
  4. Total internal attenuation

29. Quantum efficiency (η) is defined as

Answers:

  1. a
  2. b
  3. c
  4. d

30. Which of the following is an Optical System Design Software?

Answers:

  1. MATLAB
  2. COMSIM
  3. Photonic Transmission Design Suite (PTDS)
  4. ORCAD

31. COBRA (commutateur optique binaire rapide) is an ________.

Answers:

  1. optical fiber
  2. optical source
  3. optical detector
  4. optical switch

32. For a multimode optical graded index fiber, the profile parameter (α) will be equal to:

Answers:

  1. Zero
  2. 1
  3. 2

33. What would the optical return loss (ORL) be defined as when r-fresnal reflection occurs at a fiber-air interface?

Answers:

  1. ORL= -10log10r
  2. ORL= -20log10r
  3. ORL= -30log10r
  4. ORL= -10loger

34. When microwave frequency rather than radio frequency subcarriers are employed, the strategy is usually referred to as ______.

Answers:

  1. Time division multiplexing
  2. Frequency division multiplexing
  3. Code-division multiplexing
  4. Subcarrier multiplexing (SCM)

35. FDDI can support a data rate of

Answers:

  1. 10 Mbps
  2. 10 Gbps
  3. 100 Mbps
  4. 1000 Mbps

36. Numerical aperture (NA) is related to the refractive indexes of core (n1) and cladding (n2) when,

Answers:

  1. a
  2. b
  3. c
  4. d

37. What does TPON stand for?

Answers:

  1. Telephony on a pure optical network
  2. Telephony on a plastic optical network
  3. Telephony on a polarized optical network
  4. Telephony on a passive optical network

38. Light emitting diodes (LED’s) are:

Answers:

  1. Monochromatic incoherent sources
  2. Monochromatic coherent sources
  3. Incandescent light sources
  4. None of the above

39. A multimode graded index fiber exhibits total pulse broadening of 0.2 µsec over a distance of 10Km. Estimate the maximum possible bandwidth assuming that there is no inter-symbol interference.

Answers:

  1. 5 MHZ
  2. 2.5 MHZ
  3. 10 MHZ
  4. 1 MHZ

40. Homodyne detection is used for _______.

Answers:

  1. incoherent systems
  2. incandescent systems
  3. coherent systems
  4. analog systems

41. Avalanche photodiodes are ________.

Answers:

  1. less sensitive than simple photodiodes
  2. more sensitive than simple photodiodes
  3. cheaper than simple photodiodes
  4. less complex in structure than simple photodiodes

42. Hydrogen absorption by optical fiber causes _______.

Answers:

  1. an increase in efficiency
  2. a decrease in optical fiber losses
  3. no effect
  4. an increase in optical fiber losses

43. For an ideal photo detector, the absorption coefficient must be ______.

Answers:

  1. low
  2. zero
  3. one
  4. large

44. Rayleigh scattering is a ________.

Answers:

  1. non-linear scattering
  2. differential scattering
  3. cumulative scattering
  4. linear scattering

45. FDDI is _______.

Answers:

  1. Fiber dual data interface
  2. Fiber distributed data interface
  3. Fiber dual data interchange
  4. Fiber distributed data interchange

46. Macro bending losses in optical fibers can be reduced by designing the fibers with ________.

Answers:

  1. a smaller refractive index difference
  2. a fiber glass
  3. a silica glass
  4. a larger refractive index difference

47. Metallic impurities are eliminated from optical fiber by:

Answers:

  1. Vapor axial deposition (VAD) method
  2. Modified chemical vapor deposition (MCVD)method
  3. Vapor-phase oxidation method
  4. Plasma-activated chemical vapor deposition (PCVD)method

48. The information carrying capacity of optical fibers is in the range of:

Answers:

  1. MHZ
  2. mHZ
  3. GHZ
  4. µHZ

49. The first generation optical fibers are fabricated from:

Answers:

  1. Silica
  2. Oxides
  3. Gallium aluminum arsenide alloys
  4. Plastic

50. The Nd:YAG LASER is a/an_______.

Answers:

  1. non semiconductor laser
  2. semiconductor laser
  3. injection laser
  4. directional laser

51. Optical time domain reflectometry (OTDR) is a/an ________.

Answers:

  1. attenuation measurement technique
  2. refractive index measurement technique
  3. field measurement technique
  4. core diameter measurement technique

52. What is the relationship between refractive index (n1) of core and refractive index (n2) of cladding for an optical fiber?

Answers:

  1. n1 < n2
  2. n1 = n2
  3. n1 < n2
  4. n1 > n2

53. SOLITON is a/an ______.

Answers:

  1. type of optical fiber
  2. optical source
  3. optical detector
  4. pulse traveling in optical fiber

54. What is signal attenuation in an optical fiber where P1=Input power and P0=Output power

Answers:

  1. a
  2. b
  3. c
  4. None of the above

55. Index optical fibers are sometimes referred to as:

Answers:

    • Homogenous core fibers
    • Heterogeneous core fibers
    • Long fibers
    • Short fibers

56. IEEE 802.5 is a/an ________.

Answers:

  1. Ethernet
  2. Token bus
  3. Token ring
  4. Token star

57. The cutback technique is a/an _______.

Answers:

  1. attenuation measurement technique
  2. refractive index measurement technique
  3. impurity measurement technique
  4. frequency measurement technique

58. The refractive index is defined as the ratio of ____________.

Answers:

  1. the velocity of light in a vacuum to the velocity of light in the medium
  2. the velocity of light in the medium to the velocity of sound in a vacuum
  3. the velocity of light in the medium to the velocity of light in a vacuum

59. The population inversion phenomenon in optical sources occurs when _________.

Answers:

  1. the population of atoms in the upper energy level is greater than in the lower energy level
  2. the population of atoms in the lower energy level is greater than in the upper energy level
  3. the population of atoms in the upper and lower energy levels is equal
  4. None of the above

60. Intermodal dispersion is less in a __________.

Answers:

  1. Multimode step index fiber
  2. Multimode graded index fiber
  3. Single mode step index fiber
  4. Single mode graded index fiber

61. The fiber gyroscope is an ______.

Answers:

  1. Intrinsic fiber sensor
  2. Interferometer fiber sensor
  3. Extrinsic fiber sensor
  4. Extinction fiber sensor

62. One polarization maintaining fiber operates at a wavelength of 1.5 µm and has a beat length of 0.6mm. Its modal birefringence is given by _______.

Answers:

  1. 1.5 x 10-3
  2. 3.5 x 10-3
  3. 2.5 x 10-3
  4. 4.5 x 10-3

63. The output power of a LASER is greater than that of a LED because of _____.

Answers:

  1. stimulated emission
  2. spontaneous emission
  3. straight emission
  4. None of the above

64. Dispersion is low in the __________.

Answers:

  1. Multimode step index fiber
  2. Single mode step index fiber
  3. Two mode step index fiber
  4. None of the above

65. Surface emitter LEDs have high radiance because _______.

Answers:

  1. a hemisphere of n type GaAs is formed around a diffused p-type region
  2. of p-type diffusion into the n-type substrate
  3. it restricts the emission to a small active region
  4. of n-type diffusion into the p-type substrate

66. LASER stands for:

Answers:

  1. Light amplification by spontaneous emission of radiation
  2. Light amplification by stimulated emission of radiation
  3. Light amplification by straight emission of radiation
  4. None of the above

67. Dark line defects (DLDs) occur when:

Answers:

  1. non-radiative electron-hole recombination occurs
  2. mobile impurities are displaced into the active region of LASER
  3. all modes are not stabilized
  4. all modes are not polarized

68. Germanium avalanche photodiodes can be used for _______.

Answers:

  1. longer wavelength operation
  2. shorter wavelength operation
  3. low output power operation
  4. minimum noise operation

69. Which of the following is a characteristic of an injection LASER?

Answers:

  1. Frequency Chirp
  2. Amplification
  3. Frequency modulation
  4. Output power

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