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Reg No.: Name:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Seventh Semester B.Tech Degree Examination (Regular and Supplementary), December 2020
Course Code: EC405

Course Name: OPTICAL COMMUNICATION

Max. Marks: 100 Duration: 3 Hours
PARTA
Answer any two full questions, each carries 15 marks. Marks
1 a) Explain the general light wave system with figure. (5)
b) Write a short note on scattering losses. (5)

c) Consider a multimode fiber that has a core refractive index ൩ 51.48 and a (5)
cladding index 12 = 1.46. Find (a) critical angle at the core- cladding interface,

(b) the N.A. for the fiber, and (c) the acceptance angle in air for the fiber.

2 a) Write ashort note on photonic crystal fibre with figure. (5)

b) Briefly explain operation of Surface Emitting LED with figure. (7)

c) Write a short note on Amplified Spontaneous Emission noise. (3)

3 ஐ Write a short note on bending losses in optical fiber. (5)

b) Explain the various LED characteristics. (5)

c) Write a short note on intramodal dispersion. (5)
PART छ

Answer any two full questions, each carries 15 marks.
4 a) Explain the structure of avalanche photodiode with figure. (6)
b) Consider the photons are incident on a PIN photodiode, which has a responsivity (5)

of 0.65A/W. If the optical power level is 10۷۲۷۸۲۰. Calculate the photocurrent

generated.
c) Derive expression for Quantum or Shotnoise in photodetector. (4)
5 a) Briefly explain the Link Power Budget with figure. (5)

b) Consider a LED driven circuit has a rise time of 15 ns. Taking a typical LED (6)
spectral width of 40nm and has a material dispersion related rise time degradation
of 2115 over the 6km link. Consider the receiver has 25MHz bandwidth and has
the rise time degradation from the receiver is 1405. If the selected fiber has a
400MHz.km bandwidth-distance product with q (parameter) = 0.7, and the modal-
dispersion-induced fiber rise time is 3.9ns. Find the value of link rise time.

©) Write a short note on GH effect. (4)

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