McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electronics and Telecommunication Engineering [ENTC] .
| 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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