SREE SOWDAMBIKA COLLEGE OF ENGINEERING
DEPARTMENT OF ECE
EC8751-OPTICAL COMMUNICATION
MULIPLE 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
2. Who proposed the use of clad waveguide structure?
a) Edward Appleton
b) Schriever
c) Kao and Hockham
d) James Maxwell
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
4. The light sources used in fibre optics communication are :
a) LED’s and Lasers
b) Phototransistors
c) Xenon lights
d) Incandescent
5. The ________ ray passes through the axis of the fiber core.
a) Reflected
b) Refracted
c) Meridional
d) Shew
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
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
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
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
10. 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
11. _____________ 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)
12. 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
13. P2O5 is used as a _____________
a) Dopant
b) Starting material
c) Cladding glass
d) Core glass
14. How many types of vapor-phase deposition techniques are present?
a) One
b) Two
c) Three
d) Four
15. ___________ 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
16. Complete the given reaction.
SiCl4 + 2H2O → SiO2 + ______
a) 2HCl
b) 4HCl
c) 2Cl2
d) 4Cl2
17. 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
18. _________ 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)
19. 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
20. 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
21. 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
22. 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
23. 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.
24. 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
25. 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.
26. 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
27. In single mode fibers, the most beneficial index profile is
a) Step index
b) Graded index
c) Step and graded index
d) Coaxial cable
28. 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
29. 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
30. 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
31. 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
32. 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
33. 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
34. How many mechanisms are there which causes absorption?
a) One
b) Three
c) Two
d) Four
35. 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
36. The effects of intrinsic absorption can be minimized by-
a) Ionization
b) Radiation
c) Suitable choice of core and cladding components
d) Melting
37. Which of the following is not a metallic impurity found in glass in extrinsic absorption?
a) Fe2+
b) Fe3+
c) Cu
d) Si
38.. In the given equation, state what αr suggests;
a) Radius of curvature
b) Refractive index difference
c) Radiation attenuation coefficients
d) Constant of proportionality
39. 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
40. 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
41. 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
a) By operating at larger wavelengths
42. 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
43. 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
44. 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
45. Mie scattering has in-homogeneities mainly in
a) Forward direction
b) Backward direction
c) All direction
d) Core-cladding interface
46. 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
47. 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
48. 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
49. Stimulated Brillouin scattering is mainly a
a) Forward process
b) Backward process
c) Upward process
d) Downward process
50. Stimulated Raman scattering occur in
a) Forward direction
b) Backward direction
c) Upward direction
d) Forward and backward direction
51. Stimulated Raman scattering may have an optical power threshold of may be three orders of
magnitude
a) Lower than Brillouin threshold
b) Higher than Brillouin threshold
c) Same as Brillouin threshold
d) Higher than Rayleigh threshold
52. 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
53. 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
54. 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
55. 3dB optical bandwidth is always ___________ the 3dB electrical bandwidth.
a) Smaller than
b) Larger than
c) Negligible than
d) Equal to
56. 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
57. 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
58. 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
59. In waveguide dispersion, refractive index is independent of
a) Bit rate
b) Index difference
c) Velocity of medium
d) Wavelength
60.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
