Optical Communication & Networks - Dec 2013

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) Explain spontaneous emission and stimulated emission.(5 marks) 1(b) Explain bandwidth distance product.(5 marks) 1(c) Discuss in brief single mode step index index fiber and multi-mode step index fiber.(5 marks) 1(d) What are the advantages of optical fiber communication?(5 marks) 2(a) Derive the expression for numerical Aperture of a step index fiber.What will happen to N.Aa.if cladding is removed?(10 marks) 2(b) explain intermodal and intramodal dispersion in optical fibers.How does dispersion affect the transmission B.W of optical fibers.(10 marks) 3(a) What are the reasons for signal attenuation in an optical 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) Give the structure of a surface emitting LED.Compare with an edge emitting LED.(10 marks) 4(b) Explain any one fiber fabrication process with a neat diagram(10 marks) 5(a) Explain with neat sketches fiber splicing techniques.Enlist the desirable requirements of a good Fiber connector.(10 marks) 5(b) Describe quantum efficiency and responsivity of a photo defector.derive an expression for the responsivity of an intrinsic photo defector.(10 marks) 6(a) Briefly discuss the possible souces of noise in optical fiber receiver.describe in detail.what is meant by quantum noise?(10 marks) 6(b) Explain the techniques for measurement of attenuation,dispersion,refractive index and numerical aperture of a fiber.(10 marks)

Write short notes on any four:

7(a) Link power Budget(5 marks) 7(b) OTDR(5 marks) 7(c) Coherent and non-coherent optical transmission.(5 marks) 7(d) Multiplexing of optical signals(5 marks) 7(e) PIN diode.(5 marks)