Optical Fiber Communication - Jan 2013

Electronics & Communication (Semester 7)

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) list the disadvantages of coper wire at the optical frequency range.(6 marks) 1 (b) Expalain the ray theroy of the fiber,with the help of neat sketch.(8 marks) 1 (c) a silica galss fiber has a core refractive index of 1.5 and the elading refractive index of 1.45.calculate,br.critical angel for the core-cladding interface
the NA of the fiber and <br. percentage="" of="" light="" collected="" by="" the="" fiber<="" a="">

</br.></span>(6 marks) 2 (a) Describe the attenuation mechanisms In an optical fiber(10 marks) 2 (b) derive the equation for material dispersion in the optical fiber(6 marks) 2 (c) An optical signal at a specific wavelength has lost 55% of its power,after traversing 7km of fiber.what is the attenuation in dB/km of this of this fiber(4 marks) 3 (a) what are the characteristic requirements of an optical source?with the help of diagram.describe the operation of surface emitting LED.(10 marks) 3 (b) which are the noise types affecting the optical detector(3 marks) 3 (c) Describe the pin diode perfomance,using the diagram(7 marks) 4 (a) Derive an equation for power coupling to the step index fiber and graded index fiber(10 marks) 4 (b) what is equilibrium numerical aperture of a fiber?With the help of diagrams.expalin the lensing schemes for coupling improvement(10 marks) 5 (a) Discuss the error sources in the optical signal detection (7 marks) 5 (b) Derive an equation for optical receiver sensitivity.(10 marks) 5 (c) Calculate the PIN diode receiver sensitivity,if the gain of the photo detector is 1.its noise figure is 1 and bandwidth of the receiver is assumed to be half of the bit rate.Note the BER is 10^-12 and data rate is 100mb/s.(3 marks) 6 (a) Write the diagram and explain the radio over fiber links(10 marks) 6 (b) what is link power budget?with an example,explain the link power budget calculation (10 marks) 7 (a) with the help of neat diagram,expalin the link power budget calculation (8 marks) 7 (b) Describe the principles of working of isolators,circulator and ADM using suitable diagrams(12 marks) 8 (a) What are the optical amplifires ?Describe with the help of a sketch the semiconductor laser amplifire (10 marks) 8 (b) Describe the SONET optical network working with reference to suitable diagram.(10 marks)