Optical Fibre Communication - May 2015

Electronics & Telecomm. (Semester 8)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Draw the refractive index profile with dimensions of different types of Fibre.(5 marks) 1 (b) Describe the concept of WDM.(5 marks) 1 (c) Distinguish Spontaneous and Stimulated Emission.(5 marks) 1 (d) Describe the Eye diagram as applicable to Optical Fibre Communications.(5 marks) 2 (a) Explain any one Fibre fabrication process with neat diagram. Compare the different methods of fabrication.(10 marks) 2 (b) Starting from Maxwell's equation derive the wave equation for Step Index Fibre.(10 marks) 3 (a) Explain the Signal Attenuation in optical Fibre and plot the three windows.(10 marks) 3 (b) Describe the intermodal delay and intramodal dispersion in optical Fibre.(10 marks) 4 (a) Describe with diagram the structure of distributed feedback laser diode.(10 marks) 4 (b) A silicon avalanche photo-diode has a quantum efficiency of 65 percent at a wavelength of 900mm. Suppose 0.5 7mu;W of optical power produces a multiplied photo-current of 107mu;A. Find the multiplication M.(10 marks) 5 (a) Describe the different types of pre amplifiers used in optical receivers.(10 marks) 5 (b) Explain with diagram the setup for making pulse dispersion measurements in time domain.(10 marks) 6 (a) Why Link Power Budget is important in optical Fibre communication system? Explain with an example.(10 marks) 6 (b) Explain the different types of detections in Coherent systems.(10 marks)

Write short notes on any four:

7 (a) OTDR(5 marks) 7 (b) Fibre materials(5 marks) 7 (c) Zero dispersion wavelength(5 marks) 7 (d) Linearly polarised modes(5 marks) 7 (e) Mode coupling(5 marks)