1. Who proposed the idea of transmission of light via dielectric waveguide structure?
Correct : C. hondros and debye
2. Who proposed the use of clad waveguide structure?
Correct : C. kao and hockham
3. Which law gives the relationship between refractive index of the dielectric?
Correct : B. law of refraction (snell’s law).
4. The light sources used in fibre optics communication are :
Correct : A. led’s and lasers
5. The ________ ray passes through the axis of the fiber core.
Correct : C. meridional
6. Light incident on fibers of angles________the acceptance angle do not propagate into the fiber
Correct : B. greater than
7. What is the numerical aperture of the fiber if the angle of acceptance is 16 degree
Correct : D. 0.27
8. The ratio of speed of light in air to the speed of light in another medium is called as_________
Correct : D. refraction index
9. When a ray of light enters one medium from another medium, which quality will not change
Correct : B. frequency
10. 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
11. An optical fiber has a core radius 2μmand a numerical aperture of 0.1. Will this fiber operate at single mode at 600 nm?
Correct : A. yes
12. What is needed to predict the performance characteristicsics of single mode fibers?
Correct : B. geometric distribution of light in a propagating mode
13. Which equation is used to calculate MFD?
Correct : B. peterman equations
14. A single mode fiber has mode field diameter 10.2μmand V=2.20. What is the core diameter of this fiber?
Correct : D. 10.1μm
15. The difference between the modes’ refractive indices is called as
Correct : C. fiber birefringence
16. A single mode fiber has a beat length of 4cm at 1200nm. What is birefringence?
Correct : C. 3*10-5
17. How many propagation modes are present in single mode fibers?
Correct : B. two
18. Numerical aperture is constant in case of step index fiber. State whether the statement is true or false.
Correct : A. true
19. Plastic fibers are less widely used than glass fibers. State whether the statement is true or false.
Correct : A. true
20. Which equations are best suited for the study of electromagnetic wave propagation?
Correct : A. maxwell’s equations
21. When λ is optical wavelength in vacuum, k is given by k=2Π/λ. What does k stand for in the above equation?
Correct : A. phase propagation constant
22. Constructive interference occurs when total phase change after two successive reflections at upper and lower interfaces is equal to? (Where m is integer)
Correct : A. 2Πm
23. . When light is described as an electromagnetic wave, it consists of a periodically varying electric E and magnetic field H which are oriented at an angle
Correct : A. 90 degree to each other
24. A monochromatic wave propagates along a waveguide in z direction. These points of constant phase travel in constant phase travel at a phase velocity Vp is given by
Correct : A. vp=ω/β
25. A most important velocity in the study of transmission characteristics of optical fiber is
Correct : B. group velocity
26. Refraction is the
Correct : A. bending of light waves
27. The phenomenon which occurs when an incident wave strikes an interface at an angle greater than the critical angle with respect to the normal to the surface is called as
Correct : C. total internal reflection
28. Photonic crystal fibers also called as
Correct : D. holey fibers
29. Conventional optical fibers has more transmission losses than photonic crystal fibers. State whether the statement is true or false.
Correct : A. true
30. Losses in photonic crystal fibers are reduced to a level of
Correct : C. 0.3db/km
31. The high index contrast enables the PCF core to be reduced from around 8 μmin conventional fiber to
Correct : A. less than 1μm
32. The periodic arrangement of cladding air holes in photonic band gap fibers provides for the formation of a photonic band gap in the
Correct : D. transverse plane of fiber
33. In index-guided photonic crystal fiber structure, the dark areas are air holes. What does white areas suggests?
Correct : D. plasma
34. The unit of measurement of attenuation in optical fibers is
Correct : C. db/km
35. The optical fiber incurs a loss in signal power as light travels down the fiber which is called as
Correct : B. attenuation
36. If the input power 100μW is launched into 6 km of fiber, the mean optical power at the fiber output is 2μW. What is the overall signal attenuation through the fiber assuming there are no connectors or splices?
Correct : B. 16.98db
37. A device which reduces the intensity of light in optical fiber communications is
Correct : B. optical attenuator
38. . A decibel may be defined as the ratio of input and output optical power for a particular optical wavelength. State whether the following statement is true or false.
Correct : A. true
39. . When the input and output power in an optical fiber is 120μW & 3μW respectively and the length of the fiber is 8 km. What is the signal attenuation per km for the fiber?
Correct : B. 2db/km
40. A multimode step index fiber has a normalized frequency of 72. Estimate the number of guided modes.
Correct : B. 2592
41. A graded-index fiber has a core with parabolic refractive index profile of diameter of 30μm, NA=0.2, λ=1μm. Estimate the normalised frequency.
Correct : B. 18.84
42. A step-index fiber has core refractive index 1.46 and radius 4.5μm. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.
Correct : C. 1.214μm
43. One of the given statements is true for intermodal dispersion. Choose the right one.
Correct : A. low in single mode and considerable in multimode fiber
44. For lower bandwidth applications,
Correct : D. multimode fiber is advantageous
45. Most of the optical power is carried out in core region than in cladding. State true or false:
Correct : A. true
46. Meridional rays in graded index fibers follow
Correct : B. curved path along the axis
47. What is the unit of normalized frequency?
Correct : D. it is a dimensionless quantity
48. . Skew rays follow a
Correct : C. helical path
49. A graded-index fiber has a core with parabolic refractive index profile of diameter of 30μm, NA=0.2, λ=1μm. Estimate the normalised frequency.
Correct : B. 18.84
50. A step-index fiber has core refractive index 1.46 and radius 4.5μm. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.
Correct : C. 1.214μm
51. One of the given statements is true for intermodal dispersion. Choose the right one.
Correct : A. low in single mode and considerable in multimode fiber
52. Meridional rays in graded index fibers follow
Correct : B. curved path along the axis
53. What is the unit of normalized frequency?
Correct : D. it is a dimensionless quantity
54. Skew rays follow a
Correct : C. helical path
55. 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.
56. How many mechanisms are there which causes absorption?
Correct : B. three
57. Absorption losses due to atomic defects mainly include-
Correct : B. missing molecules, oxygen defects in glass
58. The effects of intrinsic absorption can be minimized by-
Correct : C. suitable choice of core and cladding components
59. Which of the following is not a metallic impurity found in glass in extrinsic absorption?
Correct : D. si
60. Optical fibers suffer radiation losses at bends or curves on their paths. State true or false
Correct : A. true
61. In the given equation, state what αr suggests;
Correct : C. radiation attenuation coefficients
62. A multimode fiber has refractive indices n1= 1.15, n2=1.11 and an operating wavelength of 0.7μm. Find the radius of curvature?
Correct : B. 9.30μm
63. 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
64. 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
65. Sharp bends or micro bends causes significant losses in fiber. State true or false
Correct : A. true
66. A multimode step index fiber has source of RMS spectral width of 60nm and dispersion parameter for fiber is 150psnm-1km-1. Estimate rms pulse broadening due to material dispersion.
Correct : C. 9.0ns km-1
67. . A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening.
Correct : A. 30.46ns/km
68. Γg= dβ / C*dk. What is β in the given equation?
Correct : B. propagation constant
69. A single mode fiber has a zero dispersion wavelength of 1.21μm and a dispersion slope of 0.08 psnm-2km-1. What is the total first order dispersion at wavelength 1.26μm.
Correct : B. -3.76psnm-1 km-1
70. The dispersion due to material, waveguide and profile are -2.8nm-1km-1, 20.1nm-1km-1 and 23.2nm-1km-1respectively. Find the total first order dispersion?
Correct : C. 40.5psnm-1 km-1
71. Dispersion-shifted single mode fibers are created by
Correct : C. decreasing fiber core diameter and increasing fractional index difference
72. An alternative modification of the dispersion characteristics of single mode fibers involves achievement of low dispersion gap over the low-loss wavelength region between –
Correct : C. 1.3 and 1.6μm
73. The fibers which relax the spectral requirements for optical sources and allow flexible wavelength division multiplying are known as-
Correct : A. dispersion-flattened single mode fiber
74. For suitable power confinement of fundamental mode, the normalized frequency v should be maintained in the range 1.5 to 2.4μm and the fractional index difference must be linearly increased as a square function while the core diameter is linearly reduced to keep v constant. This confinement is achieved by-
Correct : B. increasing level of germanium doping in fiber core
75. Any amount of stress occurring at the core-cladding interface would be reduced by grading the material composition. State whether the given statement is true or false.
Correct : A. true
76. The variant of non-zero-dispersion-shifted fiber is called as
Correct : D. negative-dispersion fiber
77. Rayleigh scattering and Mie scattering are the types of
Correct : A. linear scattering losses
78. Dominant intrinsic loss mechanism in low absorption window between ultraviolet and infrared absorption tails is
Correct : B. rayleigh scattering
79. Rayleigh scattering can be reduced by operating at smallest possible wavelengths. State whether the following statement is true or false.
Correct : B. false
80. The scattering resulting from fiber imperfections like core-cladding RI differences, diameter fluctuations, strains, and bubbles is
Correct : B. mie scattering
81. Mie scattering has in-homogeneities mainly in
Correct : A. forward direction
82. The in-homogeneities in Mie scattering can be reduced by coating of a fiber. State whether the following statement is true or false.
Correct : A. true
83. Raman and Brillouin scattering are usually observed at
Correct : C. high optical power densities
84. The phonon is a quantum of an elastic wave in a crystal lattice. State whether the given statement is true or false.
Correct : A. true
85. A single-mode optical fiber has an attenuation of 0.3dB/km when operating at wavelength of 1.1μm. The fiber core diameter is 4μmand bandwidth is 500 MHz. Find threshold optical power for stimulated Brillouin scattering.
Correct : B. 12.77 mw
86. 0.4 dB/km, 1.4μm, 6μm, 550MHz. Find threshold optical power for stimulated Raman scattering.
Correct : C. 1.18 w
87. Stimulated Brillouin scattering is mainly a
Correct : B. backward process
88. High frequency optical phonon is generated in stimulated Raman scattering. State true or false
Correct : B. true
89. For many applications which involve optical fiber transmission, an intensity modulation optical source is not required. State whether the given statement is true or false.
Correct : B. false
90. The optical source used for detection of optical signal is
Correct : B. photodiodes
91. An optical fiber behaves as a birefringence medium due to differences in
Correct : A. effective r-i and core geometry
92. The beat length in a single mode optical fiber is 8 cm, when light from a laser with a peak wavelength 0.6μm is launched into it. Estimate the modal birefringence.
Correct : A. 1×10-5
93. Beat length of a single mode optical fiber is 0.6cm. Calculate the difference between propagation constants for the orthogonal modes
Correct : D. 104.66
94. A polarization maintaining fiber operates at a wavelength 1.2μm and have a modal birefringence of 1.8*10-3. Calculate the period of perturbation.
Correct : B. 0.6 seconds
95. When two components are equally excited at the fiber input, then for polarization maintaining fibers δΓgshould be around
Correct : B. 1 ns/km
96. Polarization modal noise can _________ the performance of communication system.
Correct : A. degrade
97. What is dispersion in optical fiber communication?
Correct : B. broadening of transmitted light pulses along the channel
98. What does ISI stands for in optical fiber communication?
Correct : C. inter-symbol interference
99. 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
100. The maximum bit rate that may be obtained on an optical fiber link is 1/3Γ. State whether the given statement is true or false.