MCQOPTIONS
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MCQOPTIONS
This section includes 271 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics and Telecommunication Engineering [ENT knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
The spectral width of emission from the single mode device is |
| A. | smaller than broadened transition line-width |
| B. | larger than broadened transition line-width |
| C. | equal the broadened transition line-width |
| D. | cannot be determined |
| Answer» B. larger than broadened transition line-width | |
| 52. |
ηT Is known as slope quantum efficiency. State true or false |
| A. | true |
| B. | false |
| Answer» C. | |
| 53. |
A GaAs injection laser has a threshold current density of 2.5*103Acm-2and length and width of the cavity is 240μmand 110μm respectively. Find the threshold current for the device. |
| A. | 663 ma |
| B. | 660 ma |
| C. | 664 ma |
| D. | 712 ma |
| Answer» C. 664 ma | |
| 54. |
Which impurity is added to gallium phosphide to make it an efficient light emitter? |
| A. | silicon |
| B. | hydrogen |
| C. | nitrogen |
| D. | phosphorus |
| Answer» D. phosphorus | |
| 55. |
Population inversion is obtained at a p-n junction by |
| A. | heavy doping of p-type material |
| B. | heavy doping of n-type material |
| C. | light doping of p-type material |
| D. | heavy doping of both p-type and n-type material |
| Answer» E. | |
| 56. |
Calculate the radioactive minority carrier lifetime in gallium arsenide when the minority carriers are electrons injected into a p-type semiconductor region which has a hole concentration of 1018cm-3. The recombination coefficient for gallium arsenide is |
| A. | 2ns |
| B. | 1.39ns |
| C. | 1.56ns |
| D. | 2.12ms |
| Answer» C. 1.56ns | |
| 57. |
In the given equation, what does p stands for? |
| A. | permittivity |
| B. | probability |
| C. | holes |
| D. | crystal momentum |
| Answer» E. | |
| 58. |
A perfect semiconductor crystal containing no impurities or lattice defects is called as |
| A. | intrinsic semiconductor |
| B. | extrinsic semiconductor |
| C. | excitation |
| D. | valence electron |
| Answer» B. extrinsic semiconductor | |
| 59. |
Y3Al5 O12 Is a molecular formula for _____________ |
| A. | ytterbium aluminate |
| B. | yttrium oxide |
| C. | ytterbium oxy-aluminate |
| D. | yttrium-aluminum garnet |
| Answer» E. | |
| 60. |
The lasing output of the basic Fabry-perot cavity fiber is restricted to between ____________ |
| A. | 1 and 2 nm |
| B. | 5 and 10 nm |
| C. | 3 and 6 nm |
| D. | 15 and 30 nm |
| Answer» C. 3 and 6 nm | |
| 61. |
. _______________ fibers include addition of lead fluoride to the core glass in order to raise the relative refractive index. |
| A. | solid-state |
| B. | gaas |
| C. | semiconductor |
| D. | zblanp |
| Answer» E. | |
| 62. |
Dopants levels in glass fiber lasers are generally ___________ |
| A. | low |
| B. | high |
| C. | same as that of grin rod lens laser |
| D. | same as that of semiconductor laser |
| Answer» B. high | |
| 63. |
9. Which of the following co-dopant is not employed by neodymium and erbium doped silica fiber lasers? |
| A. | phosphorus pent oxide |
| B. | germania |
| C. | nitrogen |
| D. | alumina |
| Answer» D. alumina | |
| 64. |
In a three level system, the threshold power decreases inversely with the length of the fiber gain medium. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» C. | |
| 65. |
An injection laser has active cavity losses of 25 cm-1and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500μm. |
| A. | 46 cm-1 |
| B. | 51 cm-1 |
| C. | 50 cm-1 |
| D. | 49.07 cm-1 |
| Answer» E. | |
| 66. |
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. |
| A. | 2.8 ghz |
| B. | 1.2 ghz |
| C. | 1.6 ghz |
| D. | 2 ghz |
| Answer» D. 2 ghz | |
| 67. |
Doppler broadening is a homogeneous broadening mechanism. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» C. | |
| 68. |
A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes. |
| A. | 1×102 |
| B. | 3×106 |
| C. | 2.9×105 |
| D. | 2.2×105 |
| Answer» E. | |
| 69. |
__________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon. |
| A. | light amplification |
| B. | attenuation |
| C. | dispersion |
| D. | population inversion |
| Answer» B. attenuation | |
| 70. |
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. |
| A. | 3×10-13 |
| B. | 1.47×10-11 |
| C. | 2×10-12 |
| D. | 1.5×10-13 |
| Answer» C. 2×10-12 | |
| 71. |
The frequency of the absorbed or emitted radiation is related to difference in energy E between the higher energy state E2 and the lower energy state E1. State what h stands for in the given equation? |
| A. | gravitation constant |
| B. | planck’s constant |
| C. | permittivity |
| D. | attenuation constant |
| Answer» C. permittivity | |
| 72. |
An FBG is developed within a fiber core having a refractive index of 1.30. Find the grating period for it to reflect an optical signal with a wavelength of 1.33μm. |
| A. | 0.51 μm |
| B. | 0.58 μm |
| C. | 0.61 μm |
| D. | 0.49 μm |
| Answer» B. 0.58 μm | |
| 73. |
14. A _____________ coupler comprises a number of cascaded stages, each incorporating three or four-port FBT couplers to obtain a multiport output. |
| A. | star |
| B. | ladder |
| C. | wdm |
| D. | three-port |
| Answer» B. ladder | |
| 74. |
How many manufacturing methods are used for producing multimode fiber star couplers? |
| A. | two |
| B. | one |
| C. | three |
| D. | five |
| Answer» B. one | |
| 75. |
Calculate the splitting loss if a 30×30 port multimode fiber star coupler has 1 mW of optical power launched into an input port. |
| A. | 13 db |
| B. | 15 db |
| C. | 14.77 db |
| D. | 16.02 db |
| Answer» D. 16.02 db | |
| 76. |
A four-port FBT coupler has 60μW optical power launched into port one. The output powers at ports 2, 3, 4 are 0.0025, 18, and 22 μW respectively. Find the split ratio? |
| A. | 42% |
| B. | 46% |
| C. | 52% |
| D. | 45% |
| Answer» E. | |
| 77. |
A four-port multimode fiber FBT coupler has 50 μWoptical power launched into port 1. The measured output power at ports 2,3 and 4 are 0.003, 23.0 and 24.5 μW respectively. Determine the excess loss. |
| A. | 0.22 db |
| B. | 0.33 db |
| C. | 0.45 db |
| D. | 0.12 db |
| Answer» B. 0.33 db | |
| 78. |
Couplers insertion loss is same as that of excess loss. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» C. | |
| 79. |
The most common method for manufacturing couplers is ____________ |
| A. | wavelength division multiplexing |
| B. | lateral offset method |
| C. | semitransparent mirror method |
| D. | fused bi-conical taper (fbt) technique |
| Answer» E. | |
| 80. |
_____________ is caused by surface tension effects between the two fiber ends during fusing. |
| A. | pre-fusion |
| B. | diffusion |
| C. | self-alignment |
| D. | splicing |
| Answer» D. splicing | |
| 81. |
Mean splice insertion losses of 0.05 dB are obtained using multimode graded index fibers with the Springroove splice. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 82. |
Average insertion losses as low as _________ have been obtained with multimode graded index and single-mode fibers using ceramic capillaries. |
| A. | 0.1 db |
| B. | 0.5 db |
| C. | 0.02 db |
| D. | 0.3 db |
| Answer» B. 0.5 db | |
| 83. |
_____________ are formed by sandwiching the butted fiber ends between a V-groove glass substrate and a flat glass retainer plate. |
| A. | springroove splices |
| B. | v-groove splices |
| C. | elastic splices |
| D. | fusion splices |
| Answer» C. elastic splices | |
| 84. |
The GRIN-rod lens can produce a collimated output beam with a divergent angle αof between _____________ from a light source situated on, or near to, the opposite lens face. |
| A. | 1 to 5 degrees |
| B. | 9 to 16 degrees |
| C. | 4 to 8 degrees |
| D. | 25 to 50 degrees |
| Answer» B. 9 to 16 degrees | |
| 85. |
A graded index fiber has a parabolic refractive index profile (α=2) and core diameter of 42μm. Estimate an insertion loss due to a 2 μm lateral misalignment when there is index matching and assuming there is uniform illumination of all guided modes only. |
| A. | 0.180 |
| B. | 0.106 |
| C. | 0.280 |
| D. | 0.080 |
| Answer» E. | |
| 86. |
A step index fiber has a coupling efficiency of 0.906 with uniform illumination of all propagation modes. Find the insertion loss due to lateral misalignment? |
| A. | 0.95 db |
| B. | 0.40 db |
| C. | 0.42 db |
| D. | 0.62 db |
| Answer» D. 0.62 db | |
| 87. |
Losses caused by factors such as core-cladding diameter, numerical aperture, relative refractive index differences, different refractive index profiles, fiber faults are known as |
| A. | intrinsic joint losses |
| B. | extrinsic losses |
| C. | insertion losses |
| D. | coupling losses |
| Answer» B. extrinsic losses | |
| 88. |
Two joined graded index fibers that are perfectly aligned have refractive indices αR=1.93for receiving fiber αE= 2.15 for emitting fiber. Calculate the coupling loss |
| A. | 0.23 db |
| B. | 0.16 db |
| C. | 0.82 db |
| D. | 0.76 db |
| Answer» B. 0.16 db | |
| 89. |
Two joined step index fibers are perfectly aligned. What is the coupling loss of numerical aperture are NAR= 0.26 for emitting fiber? |
| A. | -0.828 db |
| B. | -0.010 db |
| C. | -0.32 db |
| D. | 0.32 db |
| Answer» C. -0.32 db | |
| 90. |
The ratio r = (n1 – n)/ (n1 – n) indicates |
| A. | fresnel reflection |
| B. | reflection coefficient |
| C. | refraction coefficient |
| D. | angular power distribution coefficient |
| Answer» C. refraction coefficient | |
| 91. |
What is the Young’s modulus of Kevlar, an aromatic polyester? |
| A. | 9 ×1010nm-2 |
| B. | 10 ×1010nm-2 |
| C. | 12 ×1010nm-2 |
| D. | 13 ×1010nm-2 |
| Answer» E. | |
| 92. |
What does n denotes in the equation given below, if vc is the crack velocity; A is the constant for the fiber material and KI is the strength intensity factor? |
| A. | refractive index |
| B. | stress corrosion susceptibility |
| C. | strain |
| D. | young’s modulus |
| Answer» C. strain | |
| 93. |
Calculate percentage strain at break for a Si-O bond with a fracture strength of 3.52*1010Nm-1 and Young’s modulus of 9 *109Nm-1. |
| A. | 3.1 % |
| B. | 2.8 % |
| C. | 4.5 % |
| D. | 3.9 % |
| Answer» E. | |
| 94. |
An Si-O bond with a Young’s modulus of 9*1010Nm-1 have an elliptical crack of depth 7nm. The surface energy is 2.29 J. Estimate fracture stress for silica fiber. |
| A. | 4.32*109nm-1 |
| B. | 6.32*109nm-1 |
| C. | 5.2*109nm-1 |
| D. | 3*109nm-1 |
| Answer» B. 6.32*109nm-1 | |
| 95. |
Multimode graded index fibers use incoherent source only. State whether the following statement is true or false. |
| A. | true |
| B. | false |
| Answer» C. | |
| 96. |
In single mode fibers, the most beneficial index profile is |
| A. | step index |
| B. | graded index |
| C. | step and graded index |
| D. | coaxial cable |
| Answer» C. step and graded index | |
| 97. |
Multimode graded index fibers with wavelength of 0.85μm have numerical aperture of 0.29 have core/cladding diameter of |
| A. | 62.5 μm/125 μm |
| B. | 100μm/140 μm |
| C. | 85 μm/ 125 μm |
| D. | 50 μm/ 125μm |
| Answer» C. 85 μm/ 125 μm | |
| 98. |
P2O5 is used as a _____________ |
| A. | dopant |
| B. | starting material |
| C. | cladding glass |
| D. | core glass |
| Answer» B. starting material | |
| 99. |
Graded index fibers produced by liquid-phase melting technique are less dispersive than step-index fibers. State whether the given statement is true or false. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 100. |
What is different in case of cross-phase modulation from self-phase modulation? |
| A. | overlapping but same pulses |
| B. | overlapping but distinguishable pulses |
| C. | non-overlapping and same pulses |
| D. | non-overlapping but distinguishable pulses |
| Answer» C. non-overlapping and same pulses | |