Correct : A. large core diameter & large numerical aperture
2. A typically structured glass multimode step index fiber shows as variation of attenuation in range of
Correct : C. 2.6 to 50 db km-1 at wavelength 0.85μm
3. Multimode step index fiber has a large core diameter of range is
Correct : A. 100 to 300 μm
4. Multimode step index fibers have a bandwidth of
Correct : B. 6 to 50 mhz km
5. 2 BASIC OPTICAL LAWS AND DEFINITIONS, OPTICAL MODES AND CONFIGURATIONS
Correct : B. higher purity than multimode step index fibers.
6. The performance characteristics of multimode graded index fibers are
Correct : A. better than multimode step index fibers
7. Multimode graded index fibers have overall buffer jackets same as multimode step index fibers but have core diameters
Correct : B. smaller than multimode step index fibers
8. Multimode graded index fibers use incoherent source only.
Correct : B. false
9. In single mode fibers, which is the most beneficial index profile?
Correct : B. graded index
10. Multimode graded index fibers with
Correct : A. single mode fibers
11. Single mode fibers allow single mode propagation; the cladding diameter must be at least
Correct : D. ten times the core diameter
12. A fiber which is referred as non- dispersive shifted fiber is?
Correct : C. o-band
13. Fiber mostly suited in single-wavelength transmission in O-band is?
Correct : B. standard single mode fibers
14. When the dimensions of the guide are reduced, the number of also decreases.
Correct : A. propagating nodes
15. waveguides are plagued by high losses.
Correct : D. metal-clad
16. The planar waveguides may be fabricated from glasses and other isotropic materials such as and
Correct : D. sulphur dioxide and polymers
17. Which of the following devices are less widely used in the field of optical fibre communications?
Correct : A. acousto-optic devices
18. Which of the following materials have refractive index near two?
Correct : B. zinc
19. Strip pattern in waveguide structures is obtained through
Correct : A. lithography
20. Propagation losses in slab and strip waveguides are smaller than the single mode fibre losses.
Correct : B. false
21. A passive Y-junction beam splitter is also used as a switch.
Correct : A. true
22. The linear variation of refractive index with the electric field is known as the
Correct : D. pockels effect
23. In a transverse electric magnetic wave, which of the following will be true?
Correct : D. e and h are transverse to wave direction
24. The cut off frequency of the TEM wave is
Correct : A. 0
25. Which component is non zero in a TEM wave?
Correct : A. ex
26. TEM wave can propagate in rectangular waveguides. State true/false.
Correct : B. false
27. The cut off wavelength in the TEM wave will be
Correct : C. infinity
28. The guided wavelength of a TEM wave in a waveguide having a wavelength of 5 units is
Correct : C. 5
29. The guided phase constant of a TEM wave in a waveguide with a phase constant of 2.8 units is
Correct : A. 2.8
30. Which type of transmission line accepts the TEM wave?
Correct : B. coaxial cable
31. For a TEM wave to propagate in a medium, the medium has to be
Correct : D. non dispersive
32. Stripline and parallel plate waveguides support the TEM wave. State true/false.
Correct : A. true
33. Which of the following statements best explain the concept of material absorption?
Correct : A. a loss mechanism related to the material composition and fabrication of fiber
34. How many mechanisms are there which causes absorption?
Correct : B. three
35. Absorption losses due to atomic defects mainly include
Correct : B. missing molecules, oxygen defects in glass
36. The effects of intrinsic absorption can be minimized by
Correct : C. suitable choice of core and cladding components
37. Which of the following is not a metallic impurity found in glass in extrinsic absorption?
Correct : D. si
38. Optical fibers suffer radiation losses at bends or curves on their paths.
Correct : A. true
39. In the given equation, state what αr suggests?
Correct : C. radiation attenuation coefficients
40. 15, n2 = 1.11 and an operating wavelength of 0.7μm. Find the radius of curvature?
Correct : B. 9.30μm
41. A single mode fiber has refractive indices n1=1.50, n2 = 2.23, core diameter of 8μm, wavelength = 1.5μm cutoff wavelength = 1.214μm. Find the radius of curvature?
Correct : C. 34 mm
42. How the potential macro bending losses can be reduced in case of multimode fiber?
Correct : A. by designing fibers with large relative refractive index differences
43. Sharp bends or micro bends causes significant losses in fiber.
Correct : A. true
44. measurements give an indication of the distortion to the optical signals as they propagate down optical fibers.
Correct : B. dispersion
45. How many types of mechanisms are present which produce dispersion in optical fibers?
Correct : A. three
46. In the single mode fibers, the dominant dispersion mechanism is
Correct : D. intra-modal dispersion
47. Devices such as are used to simulate the steady-state mode distribution.
Correct : C. mode scramblers
48. How many domains support the measurements of fiber dispersion?
Correct : D. two
49. The time domain dispersion measurement setup involves as the photo detector.
Correct : A. avalanche photodiode
50. In pulse dispersion measurements, the 3dB pulse broadening for the fiber is 10.5 ns/km and the length of the fiber is 1.2 km. Calculate the optical bandwidth for the fiber.
Correct : C. 41.9 mhz km
51. Frequency domain measurement is the preferred method for acquiring the bandwidth of multimode optical fibers.
Correct : A. true
52. Intra-modal dispersion tends to be dominant in multimode fibers.
Correct : B. false
53. What does ISI stand for in optical fiber communication?
Correct : C. inter-symbol interference
54. For no overlapping of light pulses down on an optical fiber link, the digital bit rate BT must be
Correct : A. less than the reciprocal of broadened pulse duration
55. The maximum bit rate that may be obtained on an optical fiber link is 1/3Γ.
Correct : B. false
56. A multimode graded index fiber exhibits a total pulse broadening of 0.15μsover a distance of 16 km. Estimate the maximum possible bandwidth, assuming no intersymbol interference.
Correct : C. 3.3 mhz
57. Chromatic dispersion is also called as intermodal dispersion.
Correct : B. false
58. The optical source used in a fiber is an injection laser with a relative spectral width σλ/λ of 0.0011 at a wavelength of 0.70μm. Estimate the RMS spectral width.
Correct : C. 0.77 nm
59. In waveguide dispersion, refractive index is independent of
Correct : D. wavelength
60. An optical fiber has core-index of 1.480 and a cladding index of 1.478. What should be the core size for single mode operation at 1310nm?
Correct : D. 6.50μm
61. An optical fiber has a core radius 2μm and a numerical aperture of 0.1. Will this fiber operate at single mode at 600 nm?
Correct : A. yes
62. What is needed to predict the performance characteristics of single mode fibers?
Correct : B. geometric distribution of light in a propagating mode
63. Which equation is used to calculate MFD?
Correct : B. peterman equations
64. A single mode fiber has mode field diameter 10.2μm and V=2.20. What is the core diameter of this fiber?
Correct : D. 10.1μm
65. The difference between the modes’ refractive indices is called as
Correct : C. fiber birefringence
66. How many propagation modes are present in single mode fibers?
Correct : B. two
67. Numerical aperture is constant in case of step index fiber.
Correct : A. true
68. Plastic fibers are less widely used than glass fibers.
Correct : A. true
69. A perfect semiconductor crystal containing no impurities or lattice defects is called as
Correct : A. intrinsic semiconductor
70. The energy-level occupation for a semiconductor in thermal equilibrium is described by the
Correct : C. fermi-dirac distribution function
71. The majority of the carriers in a p-type semiconductor are
Correct : A. holes
72. is used when the optical emission results from the application of electric field.
Correct : C. electro-luminescence
73. The recombination in indirect band-gap semiconductors is slow.
Correct : A. true
74. 21*10-10cm3s-1.
Correct : B. 1.39ns
75. Which impurity is added to gallium phosphide to make it an efficient light emitter?
Correct : C. nitrogen
76. Population inversion is obtained at a p-n junction by
Correct : D. heavy doping of both p-type and n-type material
77. A GaAs injection laser has a threshold current density of 2.5*103Acm-2 and length and width of the cavity is 240μm and 110μm respectively. Find the threshold current for the device.
Correct : B. 660 ma
78. A GaAs injection laser with an optical cavity has refractive index of 3.6. Calculate the reflectivity for normal incidence of the plane wave on the GaAs-air interface.
Correct : C. 0.32
79. A ho*mo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies.
Correct : B. false
80. How many types of hetero-junctions are available?
Correct : A. two
81. The system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region.
Correct : D. gaas/alga as dh
82. The amount of radiance in planer type of LED structures is
Correct : A. low
83. As compared to planar LED structure, Dome LEDs have External power efficiency effective emission area and radiance.
Correct : B. higher, greater, reduced
84. The techniques by Burros and Dawson in reference to ho*mo structure device is to use an etched well in GaAs structure.
Correct : A. true
85. In surface emitter LEDs, more advantage can be obtained by using
Correct : C. dh structures
86. Internal absorption in DH surface emitter Burros type LEDs is
Correct : D. very low
87. DH surface emitter generally give
Correct : A. more coupled optical power
88. In a multimode fiber, much of light coupled in the fiber from an LED is
Correct : C. lost
89. 0375 V. Determine optical power launched into fiber.
Correct : A. 0.03
90. Mesa structured SLEDs are used
Correct : C. to reduce current spreading
91. The InGaAsP is emitting LEDs are realized in terms of restricted are
Correct : A. length strip geometry
92. The active layer of E-LED is heavily doped with
Correct : A. zn
93. A device which converts electrical energy in the form of a current into optical energy is called as
Correct : A. optical source
94. How many types of sources of optical light are available?
Correct : C. three
95. Which process gives the laser its special properties as an optical source?
Correct : D. stimulated emission
96. An incandescent lamp is operating at a temperature of 1000K at an operating frequency of 5.2×1014 Hz. Calculate the ratio of stimulated emission rate to spontaneous emission rate.
Correct : B. 1.47×10-11
97. The lower energy level contains more atoms than upper level under the conditions of
Correct : C. thermal equilibrium
98. in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.
Correct : A. light amplification
99. 43 μm. Determine the number of longitudinal modes.
Correct : D. 2.2×105
100. A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.