M.Sc. (Semester IV) (CBCS) Examination Mar/Apr-2018
Electronics Science
OPTIC FIBER COMMUNICATION
Time: 2½ Hours
Max. Marks: 70
Instructions: Q. and are compulsory. Answer any three questions from Q.3 to Q.7. All questions carry equal marks. Use of nonprogrammable calculator is allowed.
Q.1
Select the most correct alternative
14
Intrinsic absorption window is
0.8 to 1.7 um
1.7 to 3.7 um
0.1 to 0.8 um
4.2 to 10 um
Graded index optical fiber behaves as the step index, when profile parameter is




Dispersion of light is low in optical fiber.
Multimode step index
Single mode step index
Multimode graded index
Single mode graded index
Core diameter of single mode step index fibers
100 to 1000
10 to 30
2 to 10
50 to 100
GaAs material is gap material.
Direct
Indirect
Both and
None of the above
gives very low loss while connecting the optical fiber.
Fusion splice
Mechanical splice
Multicarrier system
ASK heterodyne detection
Double-hetero junction LED has quantum efficiency of
90-100%
10-40%
60-80%
None of the above
In optical waveguide is absent.
Current density
Magnetic field
Electric field
Electric flux density
As per the attenuation spectra for some common mid- and far-infrared fibers, it is found that fiber has very low loss.
Sapphire
Chalcogenide glasses
Hollow glass
Fluoride glass
10) ST-connectors in optical fibers give db loss.
0.60-1.00
0.20-0.50
0.01-0.15
0.30-0.60
11) Germanium devices are used in the region.
Near infrared
Far infrared
Both and
Visible
12) Raman scattering optical power threshold is orders of magnitude greater than the Brillouin threshold.
Two
Three
Four
Five
13) Microbending losses are caused by
During the manufacturing process
Cable installation process
Due to environmental effects
All of the above
14) ferrule connectors can be assembled in housings to form multiple-fiber configurations.
Only cylindrical
Only biconical
Both cylindrical and biconical
None of the above
Q.2
Answer the following.
What is a PIN photodiode?
05
Explain Rayleigh scattering.
05
Write a note on Fusion splices.
04
Q.3
Explain in detail the following terms.
10
Total internal reflection
Acceptance angle
What are the advantages of optical fiber communication?
04
Q.4
Explain Liquid-phase techniques with suitable sketch.
10
Give a brief account of vapor axial deposition.
04
Q.5
A typical relative refractive index difference for an optical fiber designed for long distance transmission is 1%. Estimate the numerical aperture and the solid acceptance angle in air for the fiber when the core index is 1.46. Also, calculate the critical angle at the core-cladding interface within the fiber. (It may be assumed that the concepts of geometric optics hold for the fiber).
08
Write a short note on LED.
06
Q.6
What are the advantages of semiconductor injections laser over other semiconductor sources? Draw and explain schematic diagram of a GaAs homojunction injection laser.
10
What is dispersion?
04
Q.7
Draw and explain optical communication system. Discuss the applications of optical fiber.
10
Give a brief account of the mid-infrared detector.
04