McqMate
1. |
Who proposed the idea of transmission of light via dielectric waveguide structure? |
A. | christian huygens |
B. | karpon and bockham |
C. | hondros and debye |
D. | albert einstein |
Answer» C. hondros and debye |
2. |
Who proposed the use of clad waveguide structure? |
A. | edward appleton |
B. | schriever |
C. | kao and hockham |
D. | james maxwell |
Answer» C. kao and hockham |
3. |
Which law gives the relationship between refractive index of the dielectric? |
A. | law of reflection |
B. | law of refraction (snell’s law). |
C. | millman’s law |
D. | huygen’s law |
Answer» B. law of refraction (snell’s law). |
4. |
The light sources used in fibre optics communication are : |
A. | led’s and lasers |
B. | phototransistors |
C. | xenon lights |
D. | incandescent |
Answer» A. led’s and lasers |
5. |
The ________ ray passes through the axis of the fiber core. |
A. | reflected |
B. | refracted |
C. | meridional |
D. | shew |
Answer» C. meridional |
6. |
Light incident on fibers of angles________the acceptance angle do not propagate into the fiber |
A. | less than |
B. | greater than |
C. | equal to |
D. | less than and equal to |
Answer» B. greater than |
7. |
What is the numerical aperture of the fiber if the angle of acceptance is 16 degree |
A. | 0.50 |
B. | 0.36 |
C. | 0.20 |
D. | 0.27 |
Answer» D. 0.27 |
8. |
The ratio of speed of light in air to the speed of light in another medium is called as_________ |
A. | speed factor |
B. | dielectric constant |
C. | reflection index |
D. | refraction index |
Answer» D. refraction index |
9. |
When a ray of light enters one medium from another medium, which quality will not change |
A. | direction |
B. | frequency |
C. | speed |
D. | wavelength |
Answer» 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? |
A. | 7.31μm |
B. | 8.71μm |
C. | 5.26μm |
D. | 6.50μm |
Answer» 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? |
A. | yes |
B. | no |
Answer» A. yes |
12. |
What is needed to predict the performance characteristicsics of single mode fibers? |
A. | the intermodal delay effect |
B. | geometric distribution of light in a propagating mode |
C. | fractional power flow in the cladding of fiber |
D. | normalized frequency |
Answer» B. geometric distribution of light in a propagating mode |
13. |
Which equation is used to calculate MFD? |
A. | maxwell’s equations |
B. | peterman equations |
C. | allen cahn equations |
D. | boltzmann’s equations |
Answer» 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? |
A. | 11.1μm |
B. | 13.2μm |
C. | 7.6μm |
D. | 10.1μm |
Answer» D. 10.1μm |
15. |
The difference between the modes’ refractive indices is called as |
A. | polarization |
B. | cutoff |
C. | fiber birefringence |
D. | fiber splicing |
Answer» C. fiber birefringence |
16. |
A single mode fiber has a beat length of 4cm at 1200nm. What is birefringence? |
A. | 2*10-5 |
B. | 1.2*10-5 |
C. | 3*10-5 |
D. | 2 |
Answer» C. 3*10-5 |
17. |
How many propagation modes are present in single mode fibers? |
A. | one |
B. | two |
C. | three |
D. | five |
Answer» B. two |
18. |
Numerical aperture is constant in case of step index fiber. State whether the statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
19. |
Plastic fibers are less widely used than glass fibers. State whether the statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
20. |
Which equations are best suited for the study of electromagnetic wave propagation? |
A. | maxwell’s equations |
B. | allen-cahn equations |
C. | avrami equations |
D. | boltzmann’s equations |
Answer» 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? |
A. | phase propagation constant |
B. | dielectric constant |
C. | boltzmann’s constant |
D. | free-space constant |
Answer» 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) |
A. | 2Πm |
B. | Πm |
C. | Πm/4 |
D. | Πm/6 |
Answer» 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 |
A. | 90 degree to each other |
B. | less than 90 degree |
C. | greater than 90 degree |
D. | 180 degree apart |
Answer» 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 |
A. | vp=ω/β |
B. | vp=ω/c |
C. | vp=c/n |
D. | vp=mass/acceleration |
Answer» A. vp=ω/β |
25. |
A most important velocity in the study of transmission characteristics of optical fiber is |
A. | phase velocity |
B. | group velocity |
C. | normalized velocity |
D. | average velocity |
Answer» B. group velocity |
26. |
Refraction is the |
A. | bending of light waves |
B. | reflection of light waves |
C. | diffusion of light waves |
D. | refraction of light waves |
Answer» 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 |
A. | refraction |
B. | partial internal reflection |
C. | total internal reflection |
D. | limiting case of refraction |
Answer» C. total internal reflection |
28. |
Photonic crystal fibers also called as |
A. | conventional fibers |
B. | dotted fibers |
C. | stripped fibers |
D. | holey fibers |
Answer» D. holey fibers |
29. |
Conventional optical fibers has more transmission losses than photonic crystal fibers. State whether the statement is true or false. |
A. | true |
B. | false |
Answer» A. true |
30. |
Losses in photonic crystal fibers are reduced to a level of |
A. | 0.1db/km |
B. | 0.2db/km |
C. | 0.3db/km |
D. | 0.4db/km |
Answer» C. 0.3db/km |
31. |
The high index contrast enables the PCF core to be reduced from around 8 μmin conventional fiber to |
A. | less than 1μm |
B. | more than 5μm |
C. | more than 3μm |
D. | more than 2μm |
Answer» 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 |
A. | h-plane of fiber |
B. | e-plane of fiber |
C. | e-h-plane of fiber |
D. | transverse plane of fiber |
Answer» D. transverse plane of fiber |
33. |
In index-guided photonic crystal fiber structure, the dark areas are air holes. What does white areas suggests? |
A. | air |
B. | silica |
C. | water |
D. | plasma |
Answer» D. plasma |
34. |
The unit of measurement of attenuation in optical fibers is |
A. | km |
B. | db |
C. | db/km |
D. | coulomb’s |
Answer» C. db/km |
35. |
The optical fiber incurs a loss in signal power as light travels down the fiber which is called as |
A. | scattering |
B. | attenuation |
C. | absorption |
D. | refraction |
Answer» 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? |
A. | 15.23db |
B. | 16.98db |
C. | 17.12db |
D. | 16.62db |
Answer» B. 16.98db |
37. |
A device which reduces the intensity of light in optical fiber communications is |
A. | compressor |
B. | optical attenuator |
C. | barometer |
D. | reducer |
Answer» 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. |
A. | true |
B. | false |
Answer» 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? |
A. | 3db/km |
B. | 2db/km |
C. | 1db/km |
D. | 4db/km |
Answer» B. 2db/km |
40. |
A multimode step index fiber has a normalized frequency of 72. Estimate the number of guided modes. |
A. | 2846 |
B. | 2592 |
C. | 2432 |
D. | 2136 |
Answer» 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. |
A. | 19.32 |
B. | 18.84 |
C. | 16.28 |
D. | 17.12 |
Answer» 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%. |
A. | 1.326μm |
B. | 0.124μm |
C. | 1.214μm |
D. | 0.123μm |
Answer» C. 1.214μm |
43. |
One of the given statements is true for intermodal dispersion. Choose the right one. |
A. | low in single mode and considerable in multimode fiber |
B. | low in both single mode and multimode fiber |
C. | high in both single mode and multimode fiber |
D. | high in single mode and low in multimode fiber |
Answer» A. low in single mode and considerable in multimode fiber |
44. |
For lower bandwidth applications, |
A. | single mode fiber is advantageous |
B. | photonic crystal fibers are advantageous |
C. | coaxial cables are advantageous |
D. | multimode fiber is advantageous |
Answer» D. multimode fiber is advantageous |
45. |
Most of the optical power is carried out in core region than in cladding. State true or false: |
A. | true |
B. | false |
Answer» A. true |
46. |
Meridional rays in graded index fibers follow |
A. | straight path along the axis |
B. | curved path along the axis |
C. | path where rays changes angles at core-cladding interface |
D. | helical path |
Answer» B. curved path along the axis |
47. |
What is the unit of normalized frequency? |
A. | hertz |
B. | meter/sec |
C. | coulombs |
D. | it is a dimensionless quantity |
Answer» D. it is a dimensionless quantity |
48. |
. Skew rays follow a |
A. | hyperbolic path along the axis |
B. | parabolic path along the axis |
C. | helical path |
D. | path where rays changes angles at core-cladding interface |
Answer» 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. |
A. | 19.32 |
B. | 18.84 |
C. | 16.28 |
D. | 17.12 |
Answer» 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%. |
A. | 1.326μm |
B. | 0.124μm |
C. | 1.214μm |
D. | 0.123μm |
Answer» C. 1.214μm |
51. |
One of the given statements is true for intermodal dispersion. Choose the right one. |
A. | low in single mode and considerable in multimode fiber |
B. | low in both single mode and multimode fiber |
C. | high in both single mode and multimode fiber |
D. | high in single mode and low in multimode fiber |
Answer» A. low in single mode and considerable in multimode fiber |
52. |
Meridional rays in graded index fibers follow |
A. | straight path along the axis |
B. | curved path along the axis |
C. | path where rays changes angles at core-cladding interface |
D. | helical path |
Answer» B. curved path along the axis |
53. |
What is the unit of normalized frequency? |
A. | hertz |
B. | meter/sec |
C. | coulombs |
D. | it is a dimensionless quantity |
Answer» D. it is a dimensionless quantity |
54. |
Skew rays follow a |
A. | hyperbolic path along the axis |
B. | parabolic path along the axis |
C. | helical path |
D. | path where rays changes angles at core-cladding interface |
Answer» C. helical path |
55. |
Which of the following statements best explain the concept of material absorption? |
A. | a loss mechanism related to the material composition and fabrication of fiber. |
B. | a transmission loss for optical fibers. |
C. | results in attenuation of transmitted light. |
D. | causes of transfer of optical power |
Answer» A. a loss mechanism related to the material composition and fabrication of fiber. |
56. |
How many mechanisms are there which causes absorption? |
A. | one |
B. | three |
C. | two |
D. | four |
Answer» B. three |
57. |
Absorption losses due to atomic defects mainly include- |
A. | radiation |
B. | missing molecules, oxygen defects in glass |
C. | impurities in fiber material |
D. | interaction with other components of core |
Answer» B. missing molecules, oxygen defects in glass |
58. |
The effects of intrinsic absorption can be minimized by- |
A. | ionization |
B. | radiation |
C. | suitable choice of core and cladding components |
D. | melting |
Answer» C. suitable choice of core and cladding components |
59. |
Which of the following is not a metallic impurity found in glass in extrinsic absorption? |
A. | fe2+ |
B. | fe3+ |
C. | cu |
D. | si |
Answer» D. si |
60. |
Optical fibers suffer radiation losses at bends or curves on their paths. State true or false |
A. | true |
B. | false |
Answer» A. true |
61. |
In the given equation, state what αr suggests; |
A. | radius of curvature |
B. | refractive index difference |
C. | radiation attenuation coefficients |
D. | constant of proportionality |
Answer» 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? |
A. | 8.60μm |
B. | 9.30μm |
C. | 9.1μm |
D. | 10.2μm |
Answer» 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? |
A. | 12 mm |
B. | 20 mm |
C. | 34 mm |
D. | 36 mm |
Answer» C. 34 mm |
64. |
How the potential macro bending losses can be reduced in case of multimode fiber? |
A. | by designing fibers with large relative refractive index differences |
B. | by maintaining direction of propagation |
C. | by reducing the bend |
D. | by operating at larger wavelengths |
Answer» 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 |
A. | true |
B. | false |
Answer» 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. |
A. | 12.5ns km-1 |
B. | 9.6ns km-1 |
C. | 9.0ns km-1 |
D. | 10.2ns km-1 |
Answer» 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. |
A. | 30.46ns/km |
B. | 31.23ns/km |
C. | 28.12ns/km |
D. | 26.10ns/km |
Answer» A. 30.46ns/km |
68. |
Γg= dβ / C*dk. What is β in the given equation? |
A. | attenuation constant |
B. | propagation constant |
C. | boltzmann’s constant |
D. | free-space |
Answer» 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. |
A. | -2.8psnm-1 km-1 |
B. | -3.76psnm-1 km-1 |
C. | -1.2psnm-1 km-1 |
D. | 2.4psnm-1 km-1 |
Answer» 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? |
A. | 36.2psnm-1 km-1 |
B. | 38.12psnm-1 km-1 |
C. | 40.5psnm-1 km-1 |
D. | 20.9psnm-1 km-1 |
Answer» C. 40.5psnm-1 km-1 |
71. |
Dispersion-shifted single mode fibers are created by |
A. | increasing fiber core diameter and decreasing fractional index difference |
B. | decreasing fiber core diameter and decreasing fractional index difference |
C. | decreasing fiber core diameter and increasing fractional index difference |
D. | increasing fiber core diameter and increasing fractional index difference |
Answer» 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 – |
A. | 0.2 and 0.9μm |
B. | 0.1 and 0.2μm |
C. | 1.3 and 1.6μm |
D. | 2 and 3μm |
Answer» 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- |
A. | dispersion-flattened single mode fiber |
B. | dispersion-enhanced single mode fiber |
C. | dispersion-compressed single mode fiber |
D. | dispersion-standardized single mode fiber |
Answer» 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- |
A. | increasing level of silica doping in fiber core |
B. | increasing level of germanium doping in fiber core |
C. | decreasing level of silica germanium in fiber core |
D. | decreasing level of silica doping in fiber core |
Answer» 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. |
A. | true |
B. | false |
Answer» A. true |
76. |
The variant of non-zero-dispersion-shifted fiber is called as |
A. | dispersion flattened fiber |
B. | zero-dispersion fiber |
C. | positive-dispersion fiber |
D. | negative-dispersion fiber |
Answer» D. negative-dispersion fiber |
77. |
Rayleigh scattering and Mie scattering are the types of |
A. | linear scattering losses |
B. | non-linear scattering losses |
C. | fiber bends losses |
D. | splicing losses |
Answer» A. linear scattering losses |
78. |
Dominant intrinsic loss mechanism in low absorption window between ultraviolet and infrared absorption tails is |
A. | mie scattering |
B. | rayleigh scattering |
C. | stimulated raman scattering |
D. | stimulated brillouin scattering |
Answer» B. rayleigh scattering |
79. |
Rayleigh scattering can be reduced by operating at smallest possible wavelengths. State whether the following statement is true or false. |
A. | true |
B. | false |
Answer» B. false |
80. |
The scattering resulting from fiber imperfections like core-cladding RI differences, diameter fluctuations, strains, and bubbles is |
A. | rayleigh scattering |
B. | mie scattering |
C. | stimulated brillouin scattering |
D. | stimulated raman scattering |
Answer» B. mie scattering |
81. |
Mie scattering has in-homogeneities mainly in |
A. | forward direction |
B. | backward direction |
C. | all direction |
D. | core-cladding interface |
Answer» 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. |
A. | true |
B. | false |
Answer» A. true |
83. |
Raman and Brillouin scattering are usually observed at |
A. | low optical power densities |
B. | medium optical power densities |
C. | high optical power densities |
D. | threshold power densities |
Answer» 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. |
A. | true |
B. | false |
Answer» 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. |
A. | 11.20 mw |
B. | 12.77 mw |
C. | 13.08 mw |
D. | 12.12 mw |
Answer» B. 12.77 mw |
86. |
0.4 dB/km, 1.4μm, 6μm, 550MHz. Find threshold optical power for stimulated Raman scattering. |
A. | 1.98 w |
B. | 1.20 w |
C. | 1.18 w |
D. | 0.96 w |
Answer» C. 1.18 w |
87. |
Stimulated Brillouin scattering is mainly a |
A. | forward process |
B. | backward process |
C. | upward process |
D. | downward process |
Answer» B. backward process |
88. |
High frequency optical phonon is generated in stimulated Raman scattering. State true or false |
A. | false |
B. | true |
Answer» 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. |
A. | true |
B. | false |
Answer» B. false |
90. |
The optical source used for detection of optical signal is |
A. | ir sensors |
B. | photodiodes |
C. | zener diodes |
D. | transistors |
Answer» B. photodiodes |
91. |
An optical fiber behaves as a birefringence medium due to differences in |
A. | effective r-i and core geometry |
B. | core-cladding symmetry |
C. | transmission/propagation time of waves |
D. | refractive indices of glass and silica |
Answer» 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. |
A. | 1×10-5 |
B. | 3.5×10-5 |
C. | 2×10-5 |
D. | 4×10-5 |
Answer» 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 |
A. | 69.8 |
B. | 99.86 |
C. | 73.2 |
D. | 104.66 |
Answer» 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. |
A. | 0.7 seconds |
B. | 0.6 seconds |
C. | 0.23 seconds |
D. | 0.5 seconds |
Answer» B. 0.6 seconds |
95. |
When two components are equally excited at the fiber input, then for polarization maintaining fibers δΓgshould be around |
A. | 1.5ns/km |
B. | 1 ns/km |
C. | 1.2ns/km |
D. | 2ns/km |
Answer» B. 1 ns/km |
96. |
Polarization modal noise can _________ the performance of communication system. |
A. | degrade |
B. | improve |
C. | reduce |
D. | attenuate |
Answer» A. degrade |
97. |
What is dispersion in optical fiber communication? |
A. | compression of light pulses |
B. | broadening of transmitted light pulses along the channel |
C. | overlapping of light pulses on compression |
D. | absorption of light pulses |
Answer» B. broadening of transmitted light pulses along the channel |
98. |
What does ISI stands for in optical fiber communication? |
A. | invisible size interference |
B. | infrared size interference |
C. | inter-symbol interference |
D. | inter-shape interference |
Answer» C. inter-symbol interference |
99. |
For no overlapping of light pulses down on an optical fiber link, the digital bit rate BT must be: |
A. | less than the reciprocal of broadened pulse duration |
B. | more than the reciprocal of broadened pulse duration |
C. | same as that of than the reciprocal of broadened pulse duration |
D. | negligible |
Answer» 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. |
A. | true |
B. | false |
Answer» B. false |
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