Broadband Communication Systems Multiple Choice Questions
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 characteristic sics 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
101. 3dB optical bandwidth is always ___________ the 3dB electrical bandwidth.
a. smaller than
b. larger than
c. negligible than
d. equal to
Answer:
b. larger than
102. 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.
a. 4.6 mhz
b. 3.9 mhz
c. 3.3 mhz
d. 4.2 mhz
Answer:
c. 3.3 mhz
103. What is pulse dispersion per unit length if for a graded index fiber, 0.1μs pulse broadening is seen over a distance of 13 km?
a. 6.12ns/km
b. 7.69ns/km
c. 10.29ns/km
d. 8.23ns/km
Answer:
b. 7.69ns/km
104. Chromatic dispersion is also called as intermodal dispersion. State whether the given statement true or false.
a. true
b. false
Answer:
b. false
105. Chromatic dispersion is also called as intermodal dispersion. State true or false
a. true
b. false
Answer:
b. false
106. 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.
a. 1.2 nm
b. 1.3 nm
c. 0.77 nm
d. 0.98 nm
Answer:
c. 0.77 nm
107. In waveguide dispersion, refractive index is independent of
a. bit rate
b. index difference
c. velocity of medium
d. wavelength
Answer:
d. wavelength
108. Intermodal dispersion occurring in a large amount in multimode step index fiber results in
a. propagation of the fiber
b. propagating through the fiber
c. pulse broadening at output
d. attenuation of waves
Answer:
c. pulse broadening at output
109. After Total Internal Reflection the Meridional ray
a. makes an angle equal to acceptance angle with the axial ray
b. makes an angle equal to critical angle with the axial ray
c. travels parallel equal to critical angle with the axial ray
d. makes an angle equal to critical angle with the axial ray
Answer:
d. makes an angle equal to critical angle with the axial ray
110. Consider a single mode fiber having core refractive index n1= 1.5.
a. 1.00μsec
b. 0.06μsec
c. 0.90μsec
d. 0.30μsec
Answer:
b. 0.06μsec
111. A 4 km optical link consists of multimode step index fiber with core refractive index of 1.3 and a relative refractive index difference of 1%. Find the delay difference between the slowest and fastest modes at the fiber output.
a. 0.173 μsec
b. 0.152 μsec
c. 0.96 μsec
d. 0.121 μsec
Answer:
a. 0.173 μsec
112. A multimode step-index fiber has a core refractive index of 1.5 and relative refractive index difference of 1%. The length of the optical link is 6 km. Estimate the RMS pulse broadening due to intermodal dispersion on the link.
a. 92.6 ns
b. 86.7 ns
c. 69.3 ns
d. 68.32 ns
Answer:
b. 86.7 ns
113. The differential attenuation of modes reduces intermodal pulse broadening on a multimode optical link. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
114. The index profile of a core of multimode graded index fiber is given by-
a. n (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
b. n (r) = n1 [3 – 2Δ(r2/a)2]1/2; ra
d. n (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
Answer:
d. n (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
115. Intermodal dispersion in multimode fibers is minimized with the use of step-index fibers. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
116. Estimate RMS pulse broadening per km due to intermodal dispersion for multimode step index fiber where length of fiber is 4 km and pulse broadening per km is 80.6 ns.
a. 18.23ns/km
b. 20.15ns/km
c. 26.93ns/km
d. 10.23ns/km
Answer:
b. 20.15ns/km
117. Practical pulse broadening value for graded index fiber lies in the range of
a. 0.9 to 1.2 ns/km
b. 0.2 to 1 ns/km
c. 0.23 to 5 ns/km
d. 0.45 to 8 ns/km
Answer:
b. 0.2 to 1 ns/km
118. The nonlinear effects in optical fibers are large. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
119. How many categories of nonlinear effects are seen in optical fibers?
a. one
b. two
c. three
d. four
Answer:
b. two
120. Which of the following is not related to Kerr effects?
a. self-phase modulation
b. cross-phase modulation
c. four-wave mixing
d. stimulated raman scattering
Answer:
d. stimulated raman scattering
121. Linear scattering effects are _______ in nature.
a. elastic
b. non-elastic
c. mechanical
d. electrical
Answer:
a. elastic
122. Which thing is more dominant in making a fiber function as bidirectional optical amplifier?
a. core material
b. pump source
c. cladding material
d. diameter of fiber
Answer:
b. pump source
123. _________ semiconductor laser sources generally have broader bandwidths.
a. injection
b. pulsed126. Self-phase modulation can be used for
a. enhancing the core diameter
b. wavelength shifting
c. decreasing the attenuation
d. reducing the losses in the fiber
Answer:
b. wavelength shifting
124. Nonlinear effects which are defined by the intensity – dependent refractive index of the fiber are called as
a. scattering effects
b. kerr effects
c. raman effects
d. tomlinson effects
Answer:
b. kerr effects
125. Self-phase modulation causes modifications to the pulse spectrum. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
127. The beating between light at different frequencies or wavelengths in multichannel fiber transmission causes
a. attenuation
b. amplitude modulation of channels
c. phase modulation of channels
d. loss in transmission
Answer:
c. phase modulation of channels
128. 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:
b. overlapping but distinguishable pulses
129. When three wave components co-propagate at angular frequency w1, w2, w3, then a new wave is generated at frequency w4, which is given by
a. w4 = w1-w2-w3
b. w4 =w1+w2+w3
c. w4 =w1+w2-w3
d. w4 =w1-w2+w3
Answer:
c. w4 =w1+w2-w3
130. _____________ results from case of nonlinear dispersion compensation in which the nonlinear dispersion compensation in which the nonlinear dispersion compensation in which the nonlinear chirp caused by self-phase modulation balances, postpones, the temporal broadening induced by group velocity delay.
a. four wave mixing
b. phase modulation
c. soliton propagation
d. raman scattering
Answer:
c. soliton propagation
131. What is a fundamental necessity in the fabrication of fibers for light transmission?
a. same refractive index for both core and cladding.
b. pump source
c. material composition of fiber
d. variation of refractive index inside the optical fiber
Answer:
d. variation of refractive index inside the optical fiber
132. Which materials are unsuitable for the fabrication of graded index fiber?
a. glass-like-materials
b. mono-crystalline structures
c. amorphous material
d. silica based material
Answer:
b. mono-crystalline structures
133. How many different categories are available for the methods of preparing optical glasses?
a. 1
b. 2
c. 3
d. 4
Answer:
b. 2
134. What is the first stage in liquid-phase-technique?
a. preparation of ultra-pure material powders
b. melting of materials
c. decomposition
d. crystallization
Answer:
a. preparation of ultra-pure material powders
135. Which processes are involved in the purification stage in liquid-phase-technique?
a. filtration, co-precipitation, re-crystallization
b. decomposition, filtration, drying
c. doping, drying, decomposition
d. filtration, drying, doping
Answer:
a. filtration, co-precipitation, re-crystallization
136. At what temperature range, does the melting of multi components glass systems takes place?
a. 100-300 degree celsius
b. 600-800 degree celsius
c. 900-1300 degree celsius
d. 1500-1800 degree celsius
Answer:
c. 900-1300 degree celsius
137. Fiber drawing using preform was useful for the production of graded index fibers. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
138. The minute perturbations and impurities in the fiber drawing process using preform technique can result in very high losses of
a. between 500 and 1000 db/km
b. between 100 and 300 db/km
c. between 1200 and 1600 db/km
d. more than 2000 db/km
Answer:
a. between 500 and 1000 db/km
139. The liquid-phase melting technique is used for the production of fibers
a. with a core diameter of 50μm.
b. with a core diameter less than 100μm.
c. with a core diameter more than 200μm.
d. with a core diameter of 100μm.
Answer:
c. with a core diameter more than 200μm.
140. 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:
a. true
141. Which of the following is not a technique for fabrication of glass fibers?
a. vapor phase oxidation method
b. direct melt method
c. lave ring method
d. chemical vapor deposition technique
Answer:
c. lave ring method
142. _____________ technique is method of preparing extremely pure optical glasses.
a. liquid phase (melting)
b. radio frequency induction
c. optical attenuation
d. vapor phase deposition (vpd)
Answer:
d. vapor phase deposition (vpd)
143. Which of the following materials is not used as a starting material in vapor-phase deposition technique?
a. sicl4
b. gecl4
c. o2
d. b2o3
Answer:
d. b2o3
144. P2O5 is used as a _____________
a. dopant
b. starting material
c. cladding glass
d. core glass
Answer:
a. dopant
145. How many types of vapor-phase deposition techniques are present?
a. one
b. two
c. three
d. four
Answer:
b. two
146. ___________ uses flame hydrolysis stems from work on soot processes which were used to prepare the fiber with losses below 20 dB/km.
a. outside vapor phase oxidation
b. chemical vapor deposition
c. liquid phase melting
d. crystallization
Answer:
a. outside vapor phase oxidation
147. Complete the given reaction
a. 2hcl
b. 4hcl
c. 2cl2
d. 4cl2
Answer:
b. 4hcl
148. In modified chemical vapor deposition, vapor phase reactant such as _________ pass through a hot zone.
a. halide and oxygen
b. halide and hydrogen
c. halide and silica
d. hydroxides and oxygen
Answer:
a. halide and oxygen
149. _________ is the stimulation of oxide formation by means of non-isothermal plasma maintained at low pressure in a microwave cavity surrounding the tube.
a. outside vapor phase oxidation (ovpo)
b. vapor axial deposition (vad)
c. modified chemical vapor deposition (mcvd)
d. plasma-activated chemical vapor deposition (pcvd)
Answer:
d. plasma-activated chemical vapor deposition (pcvd)
150. Only graded index fibers are made with the help of vapor-phase deposition techniques. State whether true or false.
a. true
b. false
Answer:
b. false
151. Modified Chemical Vapor Deposition (MCVD) process is also called as an inside vapor phase oxidation (IVPD) technique. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
152. Multimode step index fiber has
a. large core diameter & large numerical aperture
b. large core diameter and small numerical aperture
c. small core diameter and large numerical aperture
d. small core diameter & small numerical aperture
Answer:
a. large core diameter & large numerical aperture
153. . A typically structured glass multimode step index fiber shows as variation of attenuation in range of
a. 1.2 to 90 db km-1at wavelength 0.69μm
b. 3.2 to 30 db km-1at wavelength 0.59μm
c. 2.6 to 50 db km-1at wavelength 0.85μm
d. 1.6 to 60 db km-1at wavelength 0.90μm
Answer:
c. 2.6 to 50 db km-1at wavelength 0.85μm
154. A multimode step index fiber has a large core diameter of range
a. 100 to 300 μm
b. 100 to 300 nm
c. 200 to 500 μm
d. 200 to 500 nm
Answer:
a. 100 to 300 μm
155. Multimode step index fibers have a bandwidth of
a. 2 to 30 mhz km
b. 6 to 50 mhz km
c. 10 to 40 mhz km
d. 8 to 40 mhz km
Answer:
b. 6 to 50 mhz km
156. Multimode graded index fibers are manufactured from materials with
a. lower purity
b. higher purity than multimode step index fibers.
c. no impurity
d. impurity as same as multimode step index fibers.
Answer:
b. higher purity than multimode step index fibers.
157. The performance characteristics of multimode graded index fibers are
a. better than multimode step index fibers.
b. same as multimode step index fibers.
c. lesser than multimode step index fibers
d. negligible
Answer:
a. better than multimode step index fibers.
158. Multimode graded index fibers have overall buffer jackets same as multimode step index fibers but have core diameters
a. larger than multimode step index fibers.
b. smaller than multimode step index fibers.
c. same as that of multimode step index fibers.
d. smaller than single mode step index fibers.
Answer:
b. smaller than multimode step index fibers.
159. 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:
b. 100μm/140 μm
160. Multimode graded index fibers use incoherent source only. State whether the following statement is true or false.
a. true
b. false
Answer:
b. false
161. 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:
b. graded index
162. The fibers mostly not used nowadays for optical fiber communication system are
a. single mode fibers
b. multimode step fibers
c. coaxial cables
d. multimode graded index fibers
Answer:
a. single mode fibers
163. Single mode fibers allow single mode propagation; the cladding diameter must be at least
a. twice the core diameter
b. thrice the core diameter
c. five times the core diameter
d. ten times the core diameter
Answer:
d. ten times the core diameter
164. A fiber which is referred as non-dispersive shifted fiber is
a. coaxial cables
b. standard single mode fibers
c. standard multimode fibers
d. non zero dispersion shifted fibers
Answer:
b. standard single mode fibers
165. Standard single mode fibers (SSMF) are utilized mainly for operation in
a. c-band
b. l-band
c. o-band
d. c-band and l-band
Answer:
c. o-band
166. Fiber mostly suited in single-wavelength transmission in O-band is
a. low-water-peak non dispersion-shifted fibers
b. standard single mode fibers
c. low minimized fibers
d. non-zero-dispersion-shifted fibers
Answer:
b. standard single mode fibers
167. When optical fibers are to be installed in a working environment, the most important parameter to be considered is
a. transmission property of the fiber
b. mechanical property of the fiber
c. core cladding ratio of the fiber
d. numerical aperture of the fiber
Answer:
b. mechanical property of the fiber
168. It is not important to cover these optical fibers required for transmission. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
169. Optical fibers for communication use are mostly fabricated from
a. plastic
b. silica or multicomponent glass
c. ceramics
d. copper
Answer:
b. silica or multicomponent glass
170. 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:
a. 4.32*109nm-1
171. 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:
d. 3.9 %
172. Stress corrosion must be considered while designing and testing optical fiber cables. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
173. Which statistics are used for calculations of strengths of optical fibers?
a. edwin statistics
b. newton statistics
c. wei-bull statistics
d. gamma statistics
Answer:
c. wei-bull statistics
174. 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:
b. stress corrosion susceptibility
175. Optical fibers for communication use are mostly fabricated from
a. plastic
b. silica or multicomponent glass
c. ceramics
d. copper
Answer:
b. silica or multicomponent glass
176. 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:
a. 4.32*109nm-1
177. 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:
d. 3.9 %
178. Stress corrosion must be considered while designing and testing optical fiber cables. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
179. Which statistics are used for calculations of strengths of optical fibers?
a. edwin statistics
b. newton statistics
c. wei-bull statistics
d. gamma statistics
Answer:
c. wei-bull statistics
180. . ____________ results from small lateral forces exerted on the fiber during the cabling process.
a. attenuation
b. micro-bending
c. dispersion
d. stimulated emission
Answer:
b. micro-bending
181. Microscopic meandering of the fiber core axis that is micro-bending is caused due to
a. environmental effects
b. rough edges of the fiber
c. large diameter of core
d. polarization
Answer:
a. environmental effects
182. How many forms of modal power distribution are considered?
a. one
b. two
c. three
d. four
Answer:
b. two
183. What does micro-bending losses depend on?
a. core material
b. refractive index
c. diameter
d. mode and wavelength
Answer:
d. mode and wavelength
184. The fiber should be________________ to avoid deterioration of the optical transmission characteristics resulting from mode-coupling-induced micro-bending.
a. free from irregular external pressure
b. coupled with plastic
c. large in diameter
d. smooth and in a steady state
Answer:
a. free from irregular external pressure
185. The diffusion of hydrogen into optical fiber affects the ______________
a. transmission of optical light in the fiber
b. spectral attenuation characteristics of the fiber
c. core of the fiber
d. cladding of the fiber
Answer:
b. spectral attenuation characteristics of the fiber
186. __________ can induce a considerable amount of attenuation in optical fibers.
a. micro-bending
b. dispersion
c. diffusion of hydrogen
d. radiation exposure
Answer:
d. radiation exposure
187. The radiation-induced attenuation can be reduced through photo-bleaching. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
188. The losses due to hydrogen absorption and reaction with fiber deposits can be temporary. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
189. The losses caused due to hydrogen absorption mechanisms are in the range of
a. 20 db/km to25 db/km
b. 10 db/km to15 db/km
c. 25 db/km to50 db/km
d. 0 db/km to5 db/km
Answer:
c. 25 db/km to50 db/km
190. The cable must be designed such that the strain on the fiber in the cable does not exceed__________
a. 0.002%
b. 0.01%
c. 0.2%
d. 0.160%
Answer:
c. 0.2%
191. How many categories exists in case of cable design?
a. two
b. three
c. one
d. four
Answer:
b. three
192. How many types of buffer jackets are used in fiber buffering?
a. three
b. one
c. two
d. four
Answer:
a. three
193. Loose tube buffer jackets exhibits a low resistance to movement of the fiber. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
194. An inclusion of one or more structural members in an optical fiber so as to serve as a cable core foundation around which the buffer fibers may be wrapped is called _____________
a. attenuation
b. splicing
c. buffering
d. stranding
Answer:
d. stranding
195. Which of the following is not a strength member used in optical cable?
a. steel wire
b. germanium
c. aramid yarns
d. glass elements
Answer:
b. germanium
196. When the stranding approach consists of individual elements (e.g. single-fiber or multi fiber loose tube buffer) than the cable is termed as
a. optical unit cable
b. coaxial cable
c. layer cable
d. bare glass cable
Answer:
c. layer cable
197. The primary function of the structural member is load bearing. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
198. 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:
d. 13 ×1010nm-2
199. The cable is normally covered with an outer plastic sheath to reduce _______________
a. abrasion
b. armor
c. friction
d. dispersion
Answer:
a. abrasion
200. A measure of amount of optical fiber emitted from source that can be coupled into a fiber is termed as
a. radiance
b. angular power distribution
c. coupling efficiency
d. power-launching
Answer:
c. coupling efficiency
201. The ratio r = (n1 – n)/ (n1 – n) indicates
a. fresnel reflection
b. reflection coefficient
c. refraction coefficient
d. angular power distribution coefficient
Answer:
b. reflection coefficient
202. A GaAs optical source having a refractive index of 3.2 is coupled to a silica fiber having a refractive index of 1.42. Determine Fresnel reflection at interface in terms of percentage.
a. 13.4%
b. 17.4%
c. 17.6%
d. 14.8%
Answer:
d. 14.8%
203. A particular GaAs fiber has a Fresnel reflection magnitude of 17.6% i.e. 0.176. Find the power loss between the source and the fiber?
a. 0.86 db
b. 0.78 db
c. 0.84 db
d. 0.83 db
Answer:
c. 0.84 db
204. 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:
b. -0.010 db
205. 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:
a. 0.23 db
206. How many types of misalignments occur when joining compatible fiber?
a. one
b. two
c. five
d. three
Answer:
d. three
207. 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:
a. intrinsic joint losses
208. 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:
c. 0.42 db
209. 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:
d. 0.080
210. Determine coupling efficiency if the misalignment loss in a graded index fiber is 0.102
a. 0.136
b. 0.898
c. 0.982
d. 0.684
Answer:
b. 0.898
211. In a single mode fiber, the losses due to lateral offset and angular misalignment are given by 0.20 dB and 0.46 dB respectively. Find the total insertion loss
a. 0.66 db
b. 0.26 db
c. 0.38 db
d. 0.40 db
Answer:
a. 0.66 db
212. The intrinsic loss through a multimode fiber joint is independent of direction of propagation. State whether the given statement is true or false
a. true
b. false
Answer:
b. false
213. The expanded beam connectors use ____________ for beam expansion and reduction.
a. square micro-lens
b. oval micro-lens
c. spherical micro-lens
d. rectangular micro-lens
Answer:
c. spherical micro-lens
214. Lens-coupled expanded beam connectors exhibit average losses of _________ in case of single mode and graded index fibers.
a. 0.3 db
b. 0.7 db
c. 0.2 db
d. 1.5 db
Answer:
b. 0.7 db
215. Sapphire ball lens expanded beam design is successful than spherical lens coupled design. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
216. The fiber is positioned at the ________ of the lens in order to obtain a collimated beam and to minimize lens-to-lens longitudinal misalignment effects.
a. aperture
b. focal length
c. curve
d. exterior circumference
Answer:
b. focal length
217. ___________ exhibits a parabolic refractive index profile with a maximum at the axis similar to graded index fiber.
a. lens coupled design
b. sapphire ball lens
c. spherical micro-lens
d. grin-rod lens
Answer:
d. grin-rod lens
218. 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:
a. 1 to 5 degrees
219. In the given equation, if r is the radial distance, n is the refractive index; what does z stands for?
a. focal length
b. distance along the optical axis
c. axial angle
d. diameter
Answer:
b. distance along the optical axis
220. The majority of the GRIN-rod lenses have diameters in the range of ____________
a. 2 to 2.5 mm
b. 3 to 4 mm
c. 0.1 to 0.4 mm
d. 0.5 to 2 mm
Answer:
d. 0.5 to 2 mm
221. Which of the following factors does not cause divergence of the collimated beam from a GRIN-rod lens?
a. lens cut length
b. size of fiber core
c. refractive index profile
d. chromatic aberration
Answer:
c. refractive index profile
222. GRIN-rod lens connectors have loss characteristics which are independent of the modal power distribution in the fiber. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
223. A permanent joint formed between two different optical fibers in the field is known as a
a. fiber splice
b. fiber connector
c. fiber attenuator
d. fiber dispersion
Answer:
a. fiber splice
224. How many types of fiber splices are available?
a. one
b. two
c. three
d. four
Answer:
b. two
225. The insertion losses of the fiber splices are much less than the Fresnel reflection loss at a butted fiber joint. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
226. What is the main requirement with the fibers that are intended for splicing?
a. smooth and oval end faces
b. smooth and square end faces
c. rough edge faces
d. large core diameter
Answer:
b. smooth and square end faces
227. In score and break process, which of the following is not used as a cutting tool?
a. diamond
b. sapphire
c. tungsten carbide
d. copper
Answer:
d. copper
228. The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as
a. mechanical splicing
b. fusion splicing
c. melting
d. diffusion
Answer:
b. fusion splicing
229. Which of the following is not used as a flame heating source in fusion splicing?
a. microprocessor torches
b. ox hydric burners
c. electric arc
d. gas burner
Answer:
d. gas burner
230. 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:
a. 0.1 db
231. _____________ 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:
b. v-groove splices
232. 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:
a. true
233. Alignment accuracy of the order ___________ is obtained using the three glass rod alignment sleeve.
a. 0.23 μm
b. 0.15 μm
c. 0.05 μm
d. 0.01 μm
Answer:
c. 0.05 μm
234. In case of multiple fusion, splice losses using an electric arc fusion device with multimode graded index fiber range from
a. 0.01 to 0.04 db
b. 0.19 to 0.25 db
c. 0.12 to 0.15 db
d. 0.04 to 0.12 db
Answer:
d. 0.04 to 0.12 db
235. The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as
a. mechanical splicing
b. fusion splicing
c. melting
d. diffusion
Answer:
b. fusion splicing
236. The rounding of the fiber ends with a low energy discharge before pressing the fibers together and fusing with a stronger arc is called as
a. pre-fusion
b. diffusion
c. crystallization
d. alignment
Answer:
a. pre-fusion
237. _____________ is caused by surface tension effects between the two fiber ends during fusing.
a. pre-fusion
b. diffusion
c. self-alignment
d. splicing
Answer:
c. self-alignment
238. 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:
a. true
239. When considering source-to-fiber coupling efficiencies, the ________ is an important parameter than total output power.
a. numerical aperture
b. radiance of an optical source
c. coupling efficiency
d. angular power distribution
Answer:
b. radiance of an optical source
240. It is a device that distributes light from a main fiber into one or more branch fibers.
a. optical fiber coupler
b. optical fiber splice
c. optical fiber connector
d. optical isolator
Answer:
a. optical fiber coupler
241. Optical fiber couplers are also called as ________________
a. isolators
b. circulators
c. directional couplers
d. attenuators
Answer:
c. directional couplers
242. How many types of multiport optical fiber couplers are available at present?
a. two
b. one
c. four
d. three
Answer:
d. three
243. The optical power coupled from one fiber to another is limited by
a. numerical apertures of fibers
b. varying refractive index of fibers
c. angular power distribution at source
d. number of modes propagating in each fiber
Answer:
d. number of modes propagating in each fiber
244. ________ couplers combine the different wavelength optical signal onto the fiber or separate the different wavelength optical signal output from the fiber.
a. 3-port
b. 2*2-star
c. wdm
d. directional
Answer:
c. wdm
245. How many fabrication techniques are used for 3 port fiber couplers?
a. one
b. two
c. three
d. four
Answer:
b. two
246. 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:
d. fused bi-conical taper (fbt) technique
247. Couplers insertion loss is same as that of excess loss. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
248. 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:
a. 0.22 db
249. 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:
d. 45%
250. How many manufacturing methods are used for producing multimode fiber star couplers?
a. two
b. one
c. three
d. five
Answer:
a. two
251. 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:
c. 14.77 db
252. 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:
a. star
253. A number of three-port single-mode fiber couplers are used in the fabrication of a ladder coupler with 16 output ports. The three-port couplers each have an excess loss of 0.2 dB along with a splice loss of 0.1 dB at the interconnection of each stage. Determine the excess loss.
a. 1.9 db
b. 1.4 db
c. 0.9 db
d. 1.1 db
Answer:
d. 1.1 db
254. 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:
a. 0.51 μm
255. It is a passive device which allows the flow of optical signal power in only one direction and preventing reflections in the backward direction.
a. fiber slice
b. optical fiber connector
c. optical isolator
d. optical coupler
Answer:
c. optical isolator
256. Which feature of an optical isolator makes it attractive to use with optical amplifier?
a. low loss
b. wavelength blocking
c. low refractive index
d. attenuation
Answer:
b. wavelength blocking
257. Magneto-optic devices can be used to function as isolators. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
258. How many implementation methods are available for optical isolators?
a. one
b. four
c. two
d. three
Answer:
d. three
259. A device which is made of isolators and follows a closed loop path is called as a ____________
a. circulator
b. gyrator
c. attenuator
d. connector
Answer:
a. circulator
260. The commercially available circulators exhibit insertion losses around ________________
a. 2 db
b. 0.7 db
c. 0.2 db
d. 1 db
Answer:
d. 1 db
261. A combination of a FBG and optical isolators can be used to produce non-blocking optical wavelength division add/draw multiplexers. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
262. A device which converts electrical energy in the form of a current into optical energy is called as
a. optical source
b. optical coupler
c. optical isolator
d. circulator
Answer:
a. optical source
263. How many types of sources of optical light are available?
a. one
b. two
c. three
d. four
Answer:
c. three
264. 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:
b. planck’s constant
265. The radiation emission process (emission of a proton at frequency) can occur in __________ ways.
a. two
b. three
c. four
d. one
Answer:
a. two
266. Which process gives the laser its special properties as an optical source?
a. dispersion
b. stimulated absorption
c. spontaneous emission
d. stimulated emission
Answer:
d. stimulated emission
267. 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:
b. 1.47×10-11
268. The lower energy level contains more atoms than upper level under the conditions of ________________
a. isothermal packaging
b. population inversion
c. thermal equilibrium
d. pumping
Answer:
c. thermal equilibrium
269. __________________ 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:
a. light amplification
270. 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:
d. 2.2×105
271. 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:
c. 1.6 ghz
272. Doppler broadening is a homogeneous broadening mechanism. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
273. 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:
d. 49.07 cm-1
274. Longitudinal modes contribute only a single spot of light to the laser output. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
275. Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser.
a. 1.4×10-11
b. 1.6×10-12
c. 1×10-12
d. 6×10-11
Answer:
b. 1.6×10-12
276. ____________________ lasers are presently the major laser source for optical fiber communications
a. semiconductor
b. non-semiconductor
c. injection
d. solid-state
Answer:
c. injection
277. In Nd: YAG lasers, the maximum doping levels of neodymium is ____________
a. 0.5 %
b. 1.5 %
c. 1.8 %
d. 2 %
Answer:
b. 1.5 %
278. Which of the following is not a property of Nd: YAG laser that enables its use as an optical fiber communication source?
a. single mode operation
b. narrow line-width
c. long lifetime
d. semiconductors and integrated circuits
Answer:
d. semiconductors and integrated circuits
279. The Nd: YAG laser has a narrow line-width which is ________________
a. < 0.01 nm b. > 0.01 nm
c. > 1 mm
d. > 1.6 mm
Answer:
a. < 0.01 nm
280. The strongest pumping bands is a four level system of Nd: YAG laser at wavelength of range_________________
a. 0.25 and 0.56 nm
b. 0.75 and 0.81 nm
c. 0.12 and 0.23 nm
d. 1 and 2 nm
Answer:
b. 0.75 and 0.81 nm
281. The Nd: YAG laser is costlier than earth-doped glass fiber laser. State whether the following statement is true or false
a. true
b. false
Answer:
a. true
282. It is a resonant cavity formed by two parallel reflecting mirrors separated by a mirror separated by a medium such as air or gas
a. optical cavity
b. wheatstone’s bridge
c. oscillator
d. fabry-perot resonator
Answer:
d. fabry-perot resonator
283. 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:
b. false
284. 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:
c. nitrogen
285. 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:
a. low
286. . _______________ 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:
d. zblanp
287. 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:
b. 5 and 10 nm
288. In Fabry-perot laser, the lower threshold is obtained by
a. increasing the refractive index
b. decreasing the refractive index
c. reducing the slope efficiency
d. increasing the slope efficiency
Answer:
c. reducing the slope efficiency
289. When did the non-semiconductor laser developed?
a. 1892
b. 1946
c. 1985
d. 1993
Answer:
c. 1985
290. Y3Al5 O12 Is a molecular formula for _____________
a. ytterbium aluminate
b. yttrium oxide
c. ytterbium oxy-aluminate
d. yttrium-aluminum garnet
Answer:
d. yttrium-aluminum garnet
291. 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:
a. intrinsic semiconductor
292. The energy-level occupation for a semiconductor in thermal equilibrium is described by the
a. boltzmann distribution function
b. probability distribution function
c. fermi-dirac distribution function
d. cumulative distribution function
Answer:
c. fermi-dirac distribution function
293. What is done to create an extrinsic semiconductor?
a. refractive index is decreased
b. doping the material with impurities
c. increase the band-gap of the material
d. stimulated emission
Answer:
b. doping the material with impurities
294. The majority of the carriers in a p-type semiconductor are__________.
a. holes
b. electrons
c. photons
d. neutrons
Answer:
a. holes
295. _________________ is used when the optical emission results from the application of electric field.
a. radiation
b. efficiency
c. electro-luminescence
d. magnetron oscillator
Answer:
c. electro-luminescence
296. In the given equation, what does p stands for?
a. permittivity
b. probability
c. holes
d. crystal momentum
Answer:
d. crystal momentum
297. 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:
b. 1.39ns
298. Which impurity is added to gallium phosphide to make it an efficient light emitter?
a. silicon
b. hydrogen
c. nitrogen
d. phosphorus
Answer:
c. nitrogen
299. 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:
d. heavy doping of both p-type and n-type material
300. 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:
b. 660 ma
301. 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.
a. 0.61
b. 0.12
c. 0.32
d. 0.48
Answer:
c. 0.32
302. A homo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
303. How many types of hetero-junctions are available?
a. two
b. one
c. three
d. four
Answer:
a. two
304. The ______________ system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region.
a. inp
b. gasb
c. gaas/gasb
d. gaas/alga as dh
Answer:
d. gaas/alga as dh
305. Stimulated emission by recombination of injected carriers is encouraged in
a. semiconductor injection laser
b. gas laser
c. chemist laser
d. dye laser
Answer:
a. semiconductor injection laser
306. In semiconductor injection laser, narrow line bandwidth is of the order
a. 1 nm or less
b. 4 nm
c. 5 nm
d. 3 nm
Answer:
a. 1 nm or less
307. Injection laser have a high threshold current density of
a. 104acm-2and more
b. 102acm-2
c. 10-2acm-2
d. 10-3acm-2
Answer:
a. 104acm-2and more
308. ηT Is known as slope quantum efficiency. State true or false
a. true
b. false
Answer:
b. false
309. The total efficiency of an injection laser with GaAs active region is 12%. The applied voltage is 3.6 V and band gap energy for GaAs is 2.34 eV. Determine external power efficiency.
a. 7.8 %
b. 10 %
c. 12 %
d. 6 %
Answer:
a. 7.8 %
310. In a DH laser, the sides of cavity are formed by _______________
a. cutting the edges of device
b. roughening the edges of device
c. softening the edges of device
d. covering the sides with ceramics
Answer:
b. roughening the edges of device
311. A particular laser structure is designed so that the active region extends the edges of devices. State whether the following statement is true or false.
a. true
b. false
Answer:
a. true
312. Gain guided laser structure are
a. chemical laser
b. gas laser
c. dh injection laser
d. quantum well laser
Answer:
c. dh injection laser
313. Laser modes are generally separated by few
a. tenths of micrometer
b. tenths of nanometer
c. tenths of pico-meter
d. tenths of millimeter
Answer:
b. tenths of nanometer
314. 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:
a. smaller than broadened transition line-width
315. Single longitudinal mode operation is obtained by
a. eliminating all transverse mode
b. eliminating all longitudinal modes
c. increasing the length of cavity
d. reducing the length of cavity
Answer:
d. reducing the length of cavity
316. A correct DH structure will restrict the vertical width of waveguide region
a. 0.5μm.
b. 0.69 μm
c. 0.65 μm
d. less than 0.4 μm
Answer:
d. less than 0.4 μm
317. The external power efficiency of an injection laser with a GaAs is 13% having band gap energy of 1.64 eV. Determine external power efficiency
a. 0.198
b. 0.283
c. 0.366
d. 0.467
Answer:
a. 0.198
318. The strip width of injection laser is
a. 12 μm
b. 11.5 μm
c. less than 10 μm
d. 15 μm
Answer:
c. less than 10 μm
319. Some refractive index variation is introduced into lateral structure of laser. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
320. Buried hetero-junction (BH) device is a type of _____________ laser where the active volume is buried in a material of wider band-gap and lower refractive index.
a. gas lasers.
b. gain guided lasers.
c. weak index guiding lasers.
d. strong index guiding lasers.
Answer:
d. strong index guiding lasers.
321. In Buried hetero-junction (BH) lasers, the optical field is confined within
a. transverse direction.
b. lateral direction.
c. outside the strip.
d. both transverse and lateral direction.
Answer:
d. both transverse and lateral direction.
322. A double-channel planar buried hetero-structure (DCP BH) has a planar active region, the confinement material is
a. alga as
b. ingaasp
c. gaas
d. sio2
Answer:
b. ingaasp
323. Problems resulting from parasitic capacitances can be overcome
a. through regrowth of semi-insulating material.
b. by using oxide material.
c. by using a planar ingaasp active region.
d. by using a algaas active region.
Answer:
a. through regrowth of semi-insulating material.
324. Quantum well lasers are also known as
a. bh lasers.
b. dh lasers.
c. chemical lasers.
d. gain-guided lasers.
Answer:
b. dh lasers.
325. Quantum well lasers are providing high inherent advantage over
a. chemical lasers.
b. gas lasers.
c. conventional dh devices.
d. bh device.
Answer:
c. conventional dh devices.
326. Strip geometry of a device or laser is important. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
327. Better confinement of optical mode is obtained in
a. multi quantum well lasers.
b. single quantum well lasers.
c. gain guided lasers.
d. bh lasers.
Answer:
a. multi quantum well lasers.
328. Multi-quantum devices have superior characteristics over
a. bh lasers.
b. dh lasers.
c. gain guided lasers.
d. single-quantum-well devices.
Answer:
b. dh lasers.
329. Dot-in-well device is also known as
a. dh lasers.
b. bh lasers.
c. qd lasers.
d. gain guided lasers.
Answer:
c. qd lasers.
330. A BH can have anything from a single electron to several electrons. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
331. QD lasers have a very low threshold current densities of range
a. 0.5 to 5 a cm-2
b. 2 to 10 a cm-2
c. 10 to 30 a cm-2
d. 6 to 20 a cm-2
Answer:
d. 6 to 20 a cm-2
332. __________________ may be improved through the use of frequency-selective feedback so that the cavity loss is different for various longitudinal modes.
a. frequency selectivity
b. longitudinal mode selectivity
c. electrical feedback
d. dissipated power
Answer:
b. longitudinal mode selectivity
333. Device which apply the frequency-selective feedback technique to provide single longitudinal operation are referred to as ________________
a. dsm lasers
b. nd: yag lasers
c. glass fiber lasers
d. qd lasers
Answer:
a. dsm lasers
334. Which of the following does not provide single frequency operation?
a. short cavity resonator
b. dsm lasers
c. coupled cavity resonator
d. fabry-perot resonator
Answer:
d. fabry-perot resonator
335. Conventional cleaved mirror structures are difficult to fabricate with the cavity lengths below
a. 200μmand greater than 150 μm
b. 100 μm and greater than 50 μm
c. 50 μm
d. 150 μm
Answer:
c. 50 μm
336. In the given equation, corrugation period is given by lλb/2Ne. If λb is the Bragg wavelength, then what does ‘l’ stand for?
a. length of cavity
b. limitation index
c. integer order of grating
d. refractive index
Answer:
c. integer order of grating
337. The first order grating (l=1) provide the strongest coupling within the device. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
338. The semiconductor lasers employing the distributed feedback mechanism are classified in _________________ categories
a. one
b. two
c. three
d. four
Answer:
b. two
339. DBF-BH lasers exhibit low threshold currents in the range of ________________
a. 40 to 50 ma
b. 21 to 30 ma
c. 2 to 5 ma
d. 10 to 20 ma
Answer:
d. 10 to 20 ma
340. Fabry-Perot devices with BH geometries high modulation speeds than DFB-BH lasers. State whether the given statement is true or false
a. true
b. false
Answer:
b. false
341. The InGaAsP/InP double channel planar DFB-BH laser with a quarter wavelength shifted first order grating provides a single frequency operation and incorporates a phase shift of ______________
a. π/2 radians
b. 2π radians
c. π radians
d. 3π/2 radians
Answer:
a. π/2 radians
342. The narrow line-width obtained under the CW operation for quarter wavelength shifted DFB laser is ________________
a. 2 mhz
b. 10 mhz
c. 3 mhz
d. 1 mhz
Answer:
c. 3 mhz
343. Line-width narrowing is achieved in DFB lasers by a strategy referred as _______________
a. noise partition
b. grating
c. tuning
d. bragg wavelength detuning
Answer:
d. bragg wavelength detuning
344. _________________ is a technique used to render the non-conducting material around the active cavity by producing permanent defects in the implanted area
a. dispersion
b. ion de-plantation
c. ion implantation
d. attenuation
Answer:
c. ion implantation
345. The threshold temperature coefficient for InGaAsP devices is in the range of
a. 10-40 k
b. 40-75 k
c. 120-190 k
d. 150-190 k
Answer:
b. 40-75 k
346. The process where the energy released during the recombination of an electron-hole event getting transferred to another carrier is known as
a. inter-valence bond absorption
b. auger recombination
c. carrier leakage effects
d. exothermic actions
Answer:
b. auger recombination
347. Auger recombination can be reduced by using
a. strained mqw structure.
b. strained sqw structure.
c. gain-guided strained structure.
d. strained quantum dots lasers.
Answer:
a. strained mqw structure.
348. High strain in strained MCQ structure should be incorporated. State whether the given statement is true or false.
a. true
b. false
Answer:
b. false
349. The parameter that prevents carrier from recombination is
a. auger recombination
b. inter-valence band absorption
c. carrier leakage
d. low temperature sensitivity
Answer:
c. carrier leakage
350. Determine the threshold current density for an AlGaAs injection laser with T0=180k at 30°C.
a. 6.24
b. 9.06
c. 3.08
d. 5.09
Answer:
d. 5.09
c. solid-state
d. silicon hybrid
Answer:
b. pulsed
351. The phenomenon occurring when the electron and photon population within the structure comes into equilibrium is known as
a. auger recombination
b. inter-valence band absorption
c. carrier leakage
d. relaxation oscillations
Answer:
d. relaxation oscillations
352. When a current pulse reaches a laser having parasitic capacitance after the initial delay time, that pulse will
a. have no effect
b. will get vanished
c. becomes narrower
d. gets broader
Answer:
d. gets broader
353. Reducing delay time and ____________ are of high importance for lasers.
a. auger recombination
b. inter-valence band absorption
c. carrier leakage effects
d. relaxation oscillations
Answer:
d. relaxation oscillations
354. Dynamic line-width broadening under the direct modulation of injection current is known as
a. auger recombination
b. inter-valence band absorption
c. carrier leakage effects
d. frequency chirping
Answer:
d. frequency chirping
355. A particular characteristic or parameter that occurs during analog transmission of injection lasers is
a. noise
b. mode hopping
c. carrier leakage effects
d. frequency chirping
Answer:
a. noise
356. Intensity of output from semiconductor injection lasers leading to optical intensity noise is due to
a. fluctuations in amplitude
b. mode hopping
c. carrier leakage effects
d. frequency chirping
Answer:
a. fluctuations in amplitude
357. In multimode lasers the optical feedback from unnecessary external reflections affecting stability of frequency and intensity is
a. remains unaffected
b. increased gradually
c. reduced
d. gets totally vanished
Answer:
c. reduced
358. Reduction in the number of modes in multimode fiber increases the mode partition noise. State whether the given statement is true or false.
a. false
b. true
Answer:
a. false
359. The behavior of laser occurring when current is increased above threshold particularly is
a. mode hopping
b. auger recombination
c. frequency chirping
d. noise
Answer:
a. mode hopping
360. ____________________ lasers are presently the major laser source for optical fiber communications
a. semiconductor
b. non-semiconductor
c. injection
d. solid-state
Answer:
c. injection
361. Which of the following is not a property of Nd: YAG laser that enables its use as an optical fiber communication source?
a. single mode operation
b. narrow line-width
c. long lifetime
d. semiconductors and integrated circuits
Answer:
d. semiconductors and integrated circuits
362. 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:
b. false
363. 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:
c. nitrogen
364. _______________ 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:
d. zblanp
365. In Fabry-perot laser, the lower threshold is obtained by
a. increasing the refractive index
b. decreasing the refractive index
c. reducing the slope efficiency
d. increasing the slope efficiency
Answer:
c. reducing the slope efficiency
366. Y3Al5 O12 Is a molecular formula for _____________
a. ytterbium aluminate
b. yttrium oxide
c. ytterbium oxy-aluminate
d. yttrium-aluminum garnet
Answer:
d. yttrium-aluminum garnet
367. Which of these factors are critical in affecting the system performance in the case of coherent optical fiber transmission?
a. laser line-width and stability
b. refractive index and index difference
c. core cladding diameter
d. frequency
Answer:
a. laser line-width and stability
368. _______________ occurs as a result of the change in lasing frequency with gain
a. frequency multiplication
b. dispersion
c. attenuation
d. line-width broadening
Answer:
d. line-width broadening
369. Laser cavity length can be extended by
a. increasing the refractive index
b. reducing frequency
c. introduction of external feedback
d. using grin-rod lenses
Answer:
c. introduction of external feedback
370. What is the purpose of wavelength dispersive element is LEC lasers?
a. wavelength selectivity
b. reduction of line-width
c. frequency multiplication
d. avalanche multiplication
Answer:
a. wavelength selectivity
371. An effective method to reduce the line-width is to make the cavity longer. State whether the following statement is true or false.
a. true
b. false
Answer:
a. true
372. Which devices are used to modulate the external cavity in order to achieve the higher switching speeds?
a. electromagnetic
b. acousto-optic
c. dispersive
d. lead
Answer:
b. acousto-optic
373. How many techniques are used to tune monolithic integrated devices (lasers)?
a. five
b. one
c. two
d. three
Answer:
c. two
374. _________________ laser can be produced when a coupler section is introduced between the amplifier and phase sections of a structure
a. sg-dbr
b. gcsr
c. y 4-shifted
d. dsm
Answer:
b. gcsr
375. The rare-earth-doped fiber lasers have spectral line-width in the range of _________________
a. 0.1 to 1 nm
b. 1.2 to 1.5 nm
c. 6 to 10 nm
d. 2 to 2.3 nm
Answer:
a. 0.1 to 1 nm
376. The lasing line-width of Fox-smith resonator is ____________________
a. less than 1 mhz
b. 1 mhz
c. 2 mhz
d. greater than 3 mhz
Answer:
a. less than 1 mhz
377. What is the widest tuning range obtained in optical fiber laser structure?
a. 60 nm
b. 80 nm
c. more than 100 nm
d. 100 nm
Answer:
c. more than 100 nm
378. The mechanism which results from a refractive index change in the passive waveguide layer is called as
a. absorption
b. spontaneous emission
c. monolithic inversion
d. bragg wavelength control
Answer:
d. bragg wavelength control
379. How many sections are included in a sampling grating distributed Bragg-reflector laser (SG-DBR)?
a. four
b. five
c. three
d. two
Answer:
b. five
380. Fiber based lasers provide diffraction-limited power at higher levels than solid-state laser. State whether the given statement is true or false
a. true
b. false
Answer:
a. true
381. The parameters having a major role in determining threshold current of efficiency of injection laser are:
a. angle recombination and optical losses
b. frequency chirping
c. relaxation oscillation
d. mode hopping
Answer:
a. angle recombination and optical losses
382. Auger current is mostly ___________________ for material with band gap providing longer wavelength emission.
a. unaffected
b. lesser
c. larger
d. vanishes
Answer:
c. larger
383. Injection lasers operating in smaller wavelengths are subjected to increased carrier losses. State whether the following statement is true or false?
a. true
b. false
Answer:
b. false
384. Devices based on quaternary PbSnSeTe and their ternary compounds, emit at wavelength ?
a. between 3-4 μm
b. longer than 4 μm
c. between 3.5 to 4.2 μm
d. between 2 to 3 μm
Answer:
b. longer than 4 μm
385. Replacing Sn with Eu, Cd or Ge in some _________________ the band gap.
a. remove the band gap
b. does not affect
c. decreases
d. increases
Answer:
d. increases
386. Lasing obtained in __________ when 191 mW of pump light at a wavelength of 0.477 μm is launched into laser.
a. ternary pbsnsete alloy laser
b. quaternary pbsnsete alloy laser
c. doped fluoro-zirconate fiber
d. ternary pbeute alloy laser
Answer:
c. doped fluoro-zirconate fiber
387. The thulium doped fiber laser when pumped with alexandrite laser output at 0.786 μm, the laser emits at
a. 0.6 μm
b. 0.8 μm
c. 2.3 μm
d. 1.2μm
Answer:
c. 2.3 μm
388. The diode-cladding-pumped Erbium praseodymium-doped fluoride device operates at wavelength.
a. around 3 μm
b. 4 μm
c. 2.6 μm
d. 1.04 μm
Answer:
a. around 3 μm
389. A technique based on inter-sub band transition is known as
a. auger recombination
b. frequency chirping
c. inter-valence band absorption
d. quantum cascading
Answer:
d. quantum cascading
390. In a QC laser, a same electron can emit number of photons. State the given statement is true or false?
a. true
b. false
Answer:
a. true
391. The phenomenon resulting in the electrons to jump from one state to another each time emitting of photon is known as :
a. inter-valence band absorption
b. mode hopping
c. quantum cascading
d. quantum confinement
Answer:
d. quantum confinement
392. A QC laser is sometimes referred as:
a. unipolar laser
b. bipolar laser
c. gain guided laser
d. non semiconductor laser
Answer:
a. unipolar laser
393. In QC lasers, it is possible to obtain different output signal wavelengths. This can be achieved by
a. inter-valence band absorption
b. mode hopping
c. quantum cascading
d. selecting layers of different thickness
Answer:
d. selecting layers of different thickness
394. QC lasers ______________ the performance characteristics.
a. have negligible effects
b. does not affects
c. improves
d. degrades
Answer:
c. improves
395. An MQW cascaded laser is more advantageous because of:
a. mode hopping
b. auger recombination
c. control over layers of material
d. properties of material
Answer:
c. control over layers of material
396. The absence of _______________ in LEDs limits the internal quantum efficiency.
a. proper semiconductor
b. adequate power supply
c. optical amplification through stimulated emission
d. optical amplification through spontaneous emission
Answer:
c. optical amplification through stimulated emission
397. The excess density of electrons Δnand holes Δpin an LED is
a. equal
b. Δpmore than Δn
c. Δn more than Δp
d. does not affects the led
Answer:
a. equal
398. The hole concentration in extrinsic materials is _________ electron concentration.
a. much greater than
b. lesser than
c. equal to
d. negligible difference with
Answer:
a. much greater than
399. In a junction diode, an equilibrium condition occurs when
a. Δngreater than Δp
b. Δnsmaller than Δp
c. constant current flow
d. optical amplification through stimulated emission
Answer:
c. constant current flow
400. Determine the total carrier recombination lifetime of a double heterojunction LED where the radioactive and nonradioactive recombination lifetime of minority carriers in active region are 70 ns and 100 ns respectively.
a. 41.17 ns
b. 35 ns
c. 40 ns
d. 37.5 ns
Answer:
a. 41.17 ns
401. Determine the internal quantum efficiency generated within a device when it has a radiative recombination lifetime of 80 ns and total carrier recombination lifetime of 40 ns.
a. 20 %
b. 80 %
c. 30 %
d. 40 %
Answer:
b. 80 %
402. Compute power internally generated within a double-heterojunction LED if it has internal quantum efficiency of 64.5 % and drive current of 40 mA with a peak emission wavelength of 0.82 μm.
a. 0.09
b. 0.039
c. 0.04
d. 0.06
Answer:
b. 0.039
403. The Lambertian intensity distribution __________ the external power efficiency by some percent.
a. reduces
b. does not affects
c. increases
d. have a negligible effect
Answer:
a. reduces
404. A planar LED fabricated from GaAs has a refractive index of 2.5. Compute the optical power emitted when transmission factor is 0.68.
a. 3.4 %
b. 1.23 %
c. 2.72 %
d. 3.62 %
Answer:
c. 2.72 %
405. A planar LED is fabricated from GaAs is having a optical power emitted is 0.018% of optical power generated internally which is 0.018% of optical power generated internally which is 0.6 P. Determine external power efficiency.
a. 0.18%
b. 0.32%
c. 0.65%
d. 0.9%
Answer:
d. 0.9%
406. For a GaAs LED, the coupling efficiency is 0.05. Compute the optical loss in decibels.
a. 12.3 db
b. 14 db
c. 13.01 db
d. 14.6 db
Answer:
c. 13.01 db
407. 13. In a GaAs LED, compute the loss relative to internally generated optical power in the fiber when there is small air gap between LED and fiber core. (Fiber coupled = 5.5 * 10-4Pint)
a. 34 db
b. 32.59 db
c. 42 db
d. 33.1 db
Answer:
b. 32.59 db
408. Determine coupling efficiency into the fiber when GaAs LED is in close proximity to fiber core having numerical aperture of 0.3
a. 0.9
b. 0.3
c. 0.6
d. 0.12
Answer:
a. 0.9
409. If a particular optical power is coupled from an incoherent LED into a low-NA fiber, the device must exhibit very high radiance . State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
410. The amount of radiance in planer type of LED structures is
a. low
b. high
c. zero
d. negligible
Answer:
a. low
411. In optical fiber communication, ______________ major types of LED structures are used
a. 2
b. 4
c. 6
d. 3
Answer:
c. 6
412. As compared to planar LED structure, Dome LEDs have ______________ External power efficiency, ____________ effective emission area and _____________ radiance.
a. greater, lesser, reduced
b. higher, greater, reduced
c. higher, lesser, increased
d. greater, greater, increased
Answer:
b. higher, greater, reduced
413. The techniques by Burros and Dawson in reference to homo structure device is to use an etched well in GaAs structure. Determine the given statement is True or false.
a. true
b. false
Answer:
a. true
414. In surface emitter LEDs, more advantage can be obtained by using
a. bh structures
b. qc structures
c. dh structures
d. gain-guided structure
Answer:
c. dh structures
415. Internal absorption in DH surface emitter Burros type LEDs is
a. cannot be determined
b. negligible
c. high
d. very low
Answer:
d. very low
416. DH surface emitter generally give
a. more coupled optical power
b. less coupled optical power
c. low current densities
d. low radiance emission into-fiber
Answer:
a. more coupled optical power
417. A DH surface emitter LED has an emission area diameter of 60μm. Determine emission area of source
a. 1.534*10-6
b. 5.423*10-3
c. 3.564*10-2
d. 2.826*10-9
Answer:
d. 2.826*10-9
418. Estimate optical power coupled into fiber of DH SLED having emission area of 1.96*10-5, radiance of 40 W/rcm2, numerical aperture of 0.2 and Fresnel reflection coefficient of 0.03 at index matched fiber surface.
a. 5.459*10-5
b. 1.784*10-3
c. 3.478*102
d. 9.551*10-5
Answer:
d. 9.551*10-5
419. In a multimode fiber, much of light coupled in the fiber from an LED is
a. increased
b. reduced
c. lost
d. unaffected
Answer:
c. lost
420. Determine the overall power conversion efficiency of lens coupled SLED having forward current of 20 mA and forward voltage of 2 V with 170 μWof optical power launched into multimode step index fiber.
a. 1.256*10-5
b. 4.417*102
c. 4.25*10-3
d. 2.14*10-3
Answer:
c. 4.25*10-3
421. The overall power conversion efficiency of electrical lens coupled LED is 0.8% and power applied 0.0375 V. Determine optical power launched into fiber
a. 0.03
b. 0.05
c. 0.3
d. 0.01
Answer:
a. 0.03
422. Mesa structured SLEDs are used
a. to reduce radiance
b. to increase radiance
c. to reduce current spreading
d. to increase current spreading
Answer:
c. to reduce current spreading
423. The InGaAsP is emitting LEDs are realized in terms of restricted
a. length strip geometry
b. radiance
c. current spreading
d. coupled optical power
Answer:
a. length strip geometry
424. The active layer of E-LED is heavily doped with
a. zn
b. eu
c. cu
d. sn
Answer:
a. zn
425. Intrinsically _________________ are a very linear device.
a. injection lasers
b. dh lasers
c. gain-guided
d. leds
Answer:
d. leds
426. Linearizing circuit techniques are used for LEDs. State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
427. The internal quantum efficiency of LEDs decreasing _______________ with ________________ temperature.
a. exponentially, decreasing
b. exponentially, increasing
c. linearly, increasing
d. linearly, decreasing
Answer:
b. exponentially, increasing
428. To utilize _____________________ of SLDs at elevated temperatures, the use of thermoelectric coolers is important.
a. low-internal efficiency
b. high-internal efficiency
c. high-power potential
d. low-power potential
Answer:
c. high-power potential
429. For particular materials with smaller bandgap energies operating in _____________ wavelength, the linewidth tends to ______________
a. 2.1 to 2.75 μm, increase
b. 1.1 to 1.7 μm, increase
c. 2.1 to 3.6 μm, decrease
d. 3.5 to 6 μm, decrease
Answer:
b. 1.1 to 1.7 μm, increase
430. The active layer composition must be adjusted if a particular center wavelength is desired.State whether the given statement is true or false.
a. true
b. false
Answer:
a. true
431. In optical fiber communication, the electrical signal dropping to half its constant value due to modulated portion of optical signal corresponds to _______
a. 6 db
b. 3 db
c. 4 db
d. 5 db
Answer:
b. 3 db
432. The optical 3 dB point occurs when currents ratio is equal to
a. ⅝
b. ⅔
c. ½
d. ¾
Answer:
c. ½
433. The optical bandwidth is _____________ the electrical bandwidth.
a. smaller
b. greater
c. same as
d. zero with respect to
Answer:
b. greater
434. When a constant d.c. drive current is applied to device, the optical o/p power is 320 μm. Determine optical o/p power when device is modulated at frequency 30 MHz with minority carrier recombination lifetime of LED i.e. 5ns.
a. 4.49*10-12
b. 6.84*10-9
c. 1.29*10-6
d. 2.29*10-4
Answer:
d. 2.29*10-4
435. The optical power at 20 MHz is 246.2 μW. Determine dc drive current applied to device with carrier recombination lifetime for LED of 6ns.
a. 3.48*10-4
b. 6.42*10-9
c. 1.48*10-3
d. 9.48*10-12
Answer:
a. 3.48*10-4
436. Determine the 3 dB electrical bandwidth at 3 dB optical bandwidth Bopt of 56.2 MHz.
a. 50.14
b. 28.1
c. 47.6
d. 61.96
Answer:
b. 28.1
437. The 3 dB electrical bandwidth B is 42 MHz. Determine 3dB optical bandwidth Bopt:
a. 45.18
b. 59.39
c. 78.17
d. 94.14
Answer:
b. 59.39
438. Determine degradation rate βrif constant junction temperature is 17 degree celsius.
a. 7.79*10-11
b. 7.91*10-11
c. 6.86*10-11
d. 5.86*10-11
Answer:
a. 7.79*10-11
439. Determine CW operating lifetime for LED with βrt = -0.58 and degradation rate βr= 7.86*10-11 h-1.
a. 32.12
b. 42
c. 22.72
d. 23.223
Answer:
c. 22.72