Optical Communication & Networks - Dec 2012

Electronics & Telecomm. (Semester 7)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1(a) What are the advantages of Optical Fiber Communication?(5 marks) 1(b) Explain Bandwidth distance product.(5 marks) 1(c) What are Linearly Polarized modes?(5 marks) 1(d) Compare direct band and indirect band semi conductors.(5 marks) 2(a) Derive the expression for numerical aperture of a step-index fiber. What will happen to N.A. if cladding is removed?(10 marks) 2(b) Compare step index and graded index fiber.(10 marks) 3(a) Starting from Maxwell's equations, derive the wave equation for step index fiber(10 marks) 3(b) Explain the significance of V-number. Derive the expression for number of guided modes in graded index fiber.(10 marks) 4(a) What do you understand by intramodal dispersion? Derive the expression for material dispersion.(10 marks) 4(b) What are the reasons for signal attenuation in an optical fiber(10 marks) 5(a) Give the structure of the surface emitting LED. Compare with an edge emitting LED.(10 marks) 5(b) Explain Avalanche Photodiode with proper structure and electric field. What is multiplication factor?(10 marks) 6(a) What are splices? Explain different types of splices.(10 marks) 6(b) Explain Double Crucible method of fiber fabrication.(10 marks)

Write short notes on any two:

7(a) Linearly polarized modes(10 marks) 7(b) OTDR(10 marks) 7(c) Link Power Budget(10 marks)