MU Electronics and Telecom Engineering (Semester 7)
Optical Communication & Networks
December 2014
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


1 (a) Explain three operating windows in optical communication.
5 M
1 (b) State the difference between the dispersion shifted and dispersion compensated fiber.
5 M
1 (c) Compare direct band gap and indirect band gap semiconductors.
5 M
1 (d) Derive expression for responsivity of an intrinsic photo detector in terms of quantum efficiency wavelength.
5 M

2 (a) A graded index fiber has a core diameter of 45μ m. Core has a parabolic refractive index profile. The fiber has NA of 0.22 and operating at wavelength of 1.2 μm. Estimate total number of guided mode propagating in the fiber.
10 M
2 (b) Explain any one fiber fabrication process with a neat diagram. Compare the different methods of fabrication.
10 M

3 (a) Explain all aspect of link power budget and rise time budget.
10 M
3 (b) What are the factors that are responsible for optical signal attenuation and dispersion during signal propagation through optical fiber.
10 M

4 (a) A silica optical fiber with core diameter large enough to be considered by Ray theory has a core refractive index of 1.5 and cladding refractive index 1.47.
Determine
ii) The NA
iii) The Acceptance angle.
10 M
4 (b) With the help of device structure explain the working of LED and LASER with the emphasis on spontaneous and stimulated emission.
10 M

5 (a) Describe the various methods of splicing individual fibers together. Enlist the desirable requirements of good fiber conductor.
10 M
5 (b) State the working principle of Raman amplifier and state its applications.
10 M

6 (a) Explain basic principle of operation of photo detector. Explain the working of PIN diode and APD as photo detector, also compare their performance.
10 M
6 (b) Draw and explain block diagram of optical receiver along with various noise sources and relevant equations.
10 M

Write short notes on any four:
7 (a) Optical bandwidth and Electrical bandwidth
5 M
7 (b) Coherent and Non coherent optical communicator.
5 M
7 (c) OTDR
5 M
7 (d) Multiplexing of optical signals
5 M
7 (e) Linearly polarized modes
5 M



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